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Full text of "Contemporary Fixed Prosthodontics"

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Contemporary 
Fixed 

Prosthodontics 



Contemporary 

Fixed 

Prosthodontics 



Third Edition with 2800 illustrations 

STEPHEN F. ROSENSTIEL, bds, msd 

Professor and Chair 

Section of Restorative Dentistry 

Prosthodontics and Endodontics 

The Ohio State University College of Dentistry 

Columbus, Ohio 

MARTIN F. LAND, d d s , m s d 
Professor and Chair 
Department of Restorative Dentistry 
Southern Illinois University 
School of Dental Medicine 
Alton, Illinois 

JUNHEI FUJIIVLOTO, DDS, IVLSD, DDSc 

Part-Time Lecturer, Tokyo Medical and Dental University 
Director of J.F. Occlusion and Prosthodontic 

Postgraduate Course 
Private Practice, Tokyo, Japan 



Artwork for Third Edition by 
DONALD O'CONNOR 
Medical Illustrator 
St. Peters, Missouri 

A rtworkfor Second Edition by 
SANDRA CELLO-LANG 
Bio-Medical Illustrator 
Chicago, Illinois 

SUE E. COTTRILL 
Medical Illustrator 
Chicago, Illinois 

KERRIE MARZO 
Medical Illustrator 
Chicago Heights, Illinois 

A rtworkfor First Edition by 
KRYSTYNA SRODULSKI 
Medical Illustrator 
San Antonio, Texas 

Photographic Services by 
JAMES COCKERILL, RBP 
Medical and Dental Photographer 
Oak Park, Illinois 



Editor-in-Chief.. John Schrefer 
Editor: Penny Rudolph 
Developmental Editor: Kimberly Frare 
Project Manager: Linda McKinley 
Production Editor: Rich Barber 
Designer: Kathi Gosche 



THIRD EDITION 

Copyright © 2001 by Mosby, Inc. 

Previous editions copyrighted 1988, 1995. 

All rights reserved. No part of this publication may be reproduced, stored in a retrieval 
system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, 
recording, or otherwise, without prior written permission from the publisher. 

Permission to photocopy or reproduce solely for internal or personal use is permitted for 
libraries or other users registered with the Copyright Clearance Center, provided that the base 
fee of $4.00 per chapter plus $.10 per page is paid directly to the Copyright Clearance Center, 
27 Congress Street, Salem, MA 02970. This consent does not extend to other kinds of 
copying, such as copying for general distribution, for advertising or promotional purposes, for 
creating new collected works, or for resale. 

Printed in the United States of America 

Mosby, Inc. 

11830 Westline Industrial Drive 

St. Louis, Missouri 63146 

Library of Congress Cataloging in Publication Data 

International Standard Book Number 0-8151-5559-X 
01 02 03 04 05 / 9 8 7 6 5 4 3 2 1 



ipiiFiftts i€ if iiiiil 



Contributors 



ROBEIYT F. BAIMA, DDS 

Associate Professor 

Department of Periodontology and Dental Hygiene, 

Restorative Dentistry 

The University of Detroit Mercy 

School of Dentistry 

Detroit, Michigan 

WILLIAM A. BRANTLEY, PHD 

Professor and Director of the Graduate Program in Dental 

Materials 

Section of Restorative Dentistry, Prosthodontics 

and Endodontics 

The Ohio State University 

College of Dentistry 

Columbus, Ohio 

ISABELLE L. DENRY, DDS, PHD 

Associate Professor 

Section of Restorative Dentistry, Prosthodontics 

and Endodontics 

The Ohio State University 

College of Dentistry 

Columbus, Ohio 

ROBERT DUANE DOUGLAS, DMD, MS 

Assistant Professor and Section Head Fixed Prosthodontics 

Department of Restorative Dentistry 

Southern Illinois University 

School of Dental Medicine 

Alton, Illinois 

MARTIN A. FREILICH, DDS 
Associate Professor 
Department of Prosthodontics 
University of Connecticut Health Center 
Farmington, Connecticut 

ANTHONY GEGAUFF 

Associate Professor 

Section of Restorative Dentistry, Prosthodontics and 

Endodontics 

The Ohio State University 

College of Dentistry 

Columbus, Ohio 



A. JON GOLDBERG, PHD 
Associate Department of Prosthodontics 
Director Center for Biomaterials 
University of Connecticut Health Center 
Farmington, Connecticut 

JULIE A. HOLLOW AY, DDS, MS 

Associate Professor, Prosthodontics 

Section of Restorative Dentistry, Prosthodontics 

and Endodontics 

The Ohio State University 

College of Dentistry 

Columbus, Ohio 

WILLIAM M. JOHNSTON, PHD 

Professor 

Section of Restorative Dentistry, Prosthodontics 

and Endodontics 

The Ohio State University 

College of Dentistry 

Columbus, Ohio 

PETER E. LARSEN, DDS 

Professor and Chairman 

Section of Oral and Maxillofacial Surgery 

The Ohio State University 

College of Dentistry 

Columbus, Ohio 

LEON W.LAUB, PHD 
Manager of Engineering/Product Manager 
Rocky Mountain Orthodontics, Inc. 
Denver, Colorado 

EDWIN A. MCGLUMPHY, DDS, MS 

Associate Professor 

Section of Restorative Dentistry, Prosthodontics 

and Endodontics 

The Ohio State University 

College of Dentistry 

Columbus, Ohio 

DONALD A. MILLER, DDS, MS 
Private Practice Limited to Endodontics 
Diplomate, American Board of Endodontics 
Joliet, Illinois 



I 



Contributors 



JAMES L. SANDRIK, PHD 

Assistant to Associate Executive Director, 

Division of Science 

American Dental Association 

Chicago, Illinois 



VAN THOMPSON, DDS, PHD 
Professor of Prosthodontics and Biomaterials 
Department of Prosthodontics and Biomaterials 
University of Medicine and Dentistry of New Jersey 
Newark, New Jersey 






Preface 



"m 



>::i;"".';'^'>ir-hr'.t. 



"The 'odd' editions, the first, the third, fifth and so 
on, are the toughest ... by the time you get to a third 
edition, your specialty will have changed suffi- 
ciently that you will be forced to completely rethink 
the organization of your book" an experienced text- 
book author told us several years ago. He was ab- 
solutely right. Since 1988 and 1995, when the first 
and second editions of Contemporary Fixed 
Prosthodontics were published, our field has indeed 
evolved beyond previously predictable expecta- 
tions. Many of the changes are driven by technolog- 
ical developments and newly available materials. 
Some, because the practice of dentistry has experi- 
enced changes in the demand for certain services. 
Throughout the process of formulating this new 
edition, we have sought to make the text more read- 
able for the dental student while maintaining the 
core format previously so well received. Concur- 
rently, every effort was made to maintain the in- 
depth comprehensive content for the established 
practitioner, graduate student, and researcher. 

It remains a difficult task to achieve the best bal- 
ance between comprehensive incorporation of cur- 
rent needs as driven by changes in the undergradu- 
ate dental curriculum, while continuing to provide 
the reader with comprehensive and clinically 
relevant information about as broad an array of top- 
ics and techniques. Some dental schools aim to de- 
emphasize student involvement in laboratory pro- 
cedures, yet we firmly believe that, although few 
beginning dentists will achieve proficiency with the 
increasingly complicated laboratory steps, each 
graduate must have a thorough understanding of 
how dental prostheses are fabricated so he or she 
can exercise sound clinical judgment and decision 
making. Also, the dental profession must have 
ready access to a comprehensive reference that en- 
ables rapid retrieval of integrated and relevant in- 
formation. Thus, one of our challenges was to main- 
tain the comprehensive nature of the provided 
information, while subtly restructuring content so 
both novice and experienced practitioners can take 
full advantage with minimal digression to related 
but less than critical information. 



ORGANIZATION 

This edition retains the previous four- section for- 
mat: Planning and Preparation; Clinical Procedures 
Part 1; Laboratory Procedures, and Clinical Proce- 
dures Part 1 1 . Pertinent basic sciences continue to be 
presented throughout and are integrated with ap- 
plicable content. 

We are particularly grateful for the constructive 
conmnents and suggestions received from a large 
number of our colleagues who were kind enough to 
take the time to conduct an in-depth review of the 
text, and to comment and respond to a lengthy list 
of specific questions. Their recommendations to ad- 
dress specific issues, not adequately covered previ- 
ously, helped considerably in formulating the initial 
template for this revision. 

NEW TO THIS EDITION 

Content and references were thoroughly updated 
throughout, and glossaries consistent with the most 

recent edition of The Glossary of Prosthodontics Terms 

were added to provide the reader with lists of ter- 
minology relevant to the chapter topics. Selected 
key words are listed at the beginning of the chap- 
ters, to facilitate rapid information retrieval. Also, 
essay format Study Questions were added to pro- 
vide the student an opportunity to test his or her 
knowledge and comprehension after reading a 
chapter. 

Section I. This section now consists of six chap- 
ters, the previous chapter on "History, Examination, 
Diagnosis and Prognosis" having been divided into 
two separate chapters: "History Taking and Clinical 
Examination" and "Diagnostic Casts and Related 
Procedures." The section now includes additional 
step-by-step sequences of photographs of com- 
monly performed diagnostic procedures and new 
artwork to clarify hinge axis location and border 
movements. 

Section 11. The tooth preparation chapters in 
Section 1 1 were revised; new artwork was generated 
for inlays, onlays, and metal-ceramic preparations; 



I 



Preface 



and content was thoroughly updated, in particular 
for all-ceramic restorations. The Implant chapter 
was comprehensively revised to be current with 
new developments in implant prosthodontics, as 
was the chapter on Provisional Restorations. 

Section III. In an effort to emphasize the im- 
portance of the mutual collaboration between 
dentist and technician, Section III now begins with 
the chapter on Laboratory Communication. In addi- 
tion to the many new illustrations throughout the 
section, for example those on occlusal waxing, the 
chapter on Pontic Design underwent an in-depth re- 
vision. It now includes emphasis on ridge shape 
and contour of the edentulous site, pontic classifica- 
tion, and various more contemporary techniques 
than the ones previously presented. 

Similarly, the chapter on All-Ceramic Restoration 
Fabrication was again updated to incorporate the 
most recent developments and techniques. A sec- 
tion on esthetic considerations was added to the 
Color Science chapter, and a chapter on Fiber- 
Reinforced Composite Fixed Prostheses follows the 
comprehensively rewritten chapter on Resin- 
Retained Fixed Partial Dentures. 

section IV This section now includes, among 
others, a more detailed discussion on luting agents, 
in an effort to make sense out of the myriad of 
choices confronting the practitioner when attempt- 
ing to select the appropriate luting agents for vari- 
ous fixed prosthodontic procedures. The treatment 
presentations now include additional long-term fol- 
low up on simple and complex fixed prosthodontic 
treatments, emphasizing the goal of longevity when 
planning fixed prostheses. 

^jGIVING CREDIT WHERE 
CREDIT IS DUE 

After three editions, it is difficull, if not impossible, 
to be 100 percent accurate and complete in crediting 
all sources of information, ideas, illustTations, pho- 
togrnphs, and concepts. Without the selfless help 
and support of so many others, we could not have 
managed this overwhelming task. Once again, 
whenever we approached colleagues, friends, and 
manufacturers, our requests for permission to in- 
clude materials were invariably most kindly ap- 
proved. Throughout we hav^ ti\c^de every effort io 
correctly identify all sources and individuals who 

helped u& bring this mssiTirngth undertaking to a 

successful completion. We apologize for any omis- 
sions, which are certainly unintentional, and for 
which we are solely responsible. 



i|[ACKNOWLEDGMENTS 

A special thank you to , . . 

All those who contributed imselfishly to make 
this text better through donation of their time, en- 
ergy, pictures, concepts for illustrations, or clinical 
photos. 

Our reviewers who took time out of their busy 
schedules to provide input and suggestions to in- 
corporate Ln this edition: Drs. Ralph DeLong, Uni- 
versity of Minnesota; Ira Gulker, New York Univer- 
sity; Ronald Gunderson, University of Maryland; 
David Koth, University of Alabama; Xavier Lepe^ 
University of Washington; Terry Lindquist, Univer- 
sity of Iowa; Mark Richards, West Virginia Univer- 
sity; Terry Wilwerdine. Creitrhton University- Ger- 
ald Woofsey, University of Missouri Kansas City. 

James Cockerill, R.B.P., who one more time 
provided selected photographic support, building 
on his previous contributions to the first two 
editions. 

Don O'Connor, who generated all new artwork 
for this edition emulating the styles used previously 
by Krystina Srodulski for edition one, and Sandra 
Cello for edition two. 

Our contributors: Drs. Robert F. Baima, William 
Brantley, Isabelle Dcnry, Duane Douglas, Martin 
Frcilicn, Jon Goldberg, Julie Holloway, Peter Larsen, 
Donald Miller, Edwin McGlumphy, and Van 
Thompson. 

Dr. Clifford W, VanBlarcom, Chairman of the 
Nomenclature Committee of the Academy pf 
Prosthodontics, and Dr. Brien R. Lang, Chairman of 
the Editorial Council of The Journal of Prosthetic 
Dentistry, for generously supporting the integration 
of terms from The Glossary of Prosthodontic Terms into 
the various chapters. It is so importitnt when teach- 
ing a discipline to use the correct word and as Mark 
Twain put it "The difference between the right word 
and the almost right word is the difference between 
lightning and a lightning bug," 

Faculty and staff at Southern Illinois University, 
School of Dental Medicine, and The Oliio State Uni- 
versity College of Dentistry for their help in making 
an already successful text even better: especially 
Tammy Duggan, Connie Mason, and Angela Evans 
for their tireless support and Pat Uhiemeyer for 
all the time spent word processing, and Drs. James 
A. Nelson, Gaylord J. James Jr., Kenneth Seckler, 
Cornell C. Thomas, and Robert Froemling for al- 
ways bemg willmg to take on another task. 

The outstanding team at Mosby: especially 

Fenny Rudolph, Kimberly Frare, Stacy Welsh, and 

Rich Barber for their patience and understanding 
in this endeavor. They are the professionals in this 
enterprise. 



Preface 



Enid, Karen, and Yoshiko have now 'survived' 
three editions. It takes special spouses to tolerate 
prosthodontists to begin with, but to support us 
throughout the completion of yet another edition 
shows how special they truly are. 

A highly respected restorative dentist told us 
once: "It took me about 10 to 15 years after dental 
school, until I could routinely make excellent inlays 
and onlays." This illustrates but one small aspect of 



I 



the lifetime challenge that fixed prosthodontics pre- 
sents to student, practitioner, and scholar. We hope 
that this new edition may help those who are suffi- 
ciently motivated and interested to meet that chal- 
lenge successfully. 

Stephen E Rosenstiel 

Martin E Land 

Junhei Fujimoto 



Contents 



3 
4 

5 

6 
Section II 



Section I PLANNING AND 
PREPARATION, 1 

1 HISTORY TAKING AND CLINICAL 
EXAMINATION, 2 

2 DIAGNOSTIC CASTS AND RELATED 
PROCEDURES, 25 
TREATMENT PLANNING, 59 
PRINCIPLES OF OCCLUSION, 83 
PERIODONTAL CONSIDERATIONS, 108 
MOUTH PREPARATION, 135 

CLINICAL PROCEDURES - 
PART I, 165 

7 PRINCIPLES OF TOOTH 
PREPARATION, 166 

8 THE COMPLETE CAST CROWN 
PREPARATION, 202 

9 THE METAL-CERAMIC CROWN 
PREPARATION, 216 

10 THE PARTIAL VENEER CROWN, INLAY, 
AND ONLAY PREPARATIONS, 230 

1 1 TOOTH PREPARATION FOR ALL-CERAMIC 
RESTORATIONS, 262 

12 RESTORATION OF THE ENDODONTICALLY 
TREATED TOOTH, 272 

13 IMPLANT-SUPPORTED FIXED 
PROSTHESES, 313 

14 TISSUE MANAGEMENT AND IMPRESSION 
MAKING, 354 

15 PROVISIONAL RESTORATIONS, 380 

Section III LABO R ATO RY PROCEDURES, 

4iy 

16 COMMUNICATING WITH THE DENTAL 
LABORATORY, 418 



17 WORKING CASTS AND DIES, 431 

18 WAX PATTERNS, 457 

19 FRAMEWORK DESIGN AND METAL 
SELECTION FOR METAL-CERAMIC 
RESTORATIONS, 488 

20 PONTIC DESIGN, 513 

21 RETAINERS FOR REMOVABLE PARTIAL 
DENTURES, 543 

22 I NVESTING AND CASTING, 567 

23 COLOR SCIENCE, ESTHETICS, AND 
SHADE SELECTION, 592 

24 METAL-CERAMIC RESTORATIONS, 609 

25 ALL-CERAMIC RESTORATIONS, 643 

26 RESIN-RETAINED FIXED PARTIAL 
DENTURES, 673 

27 FIBER- REINFORCED COMPOSITE FIXED 
PROSTHESES, 697 

28 CONNECTORS FOR FIXED PARTIAL 
DENTURES, 707 

29 FINISHING THE CAST 
RESTORATION, 732 

Section IV CLINICAL PROCEDURES - 
PART II, 745 

30 EVALUATION, CHARACTERIZATION, 
AND GLAZING, 746 

31 LUTING AGENTS AND CEMENTATION 
PROCEDURES, 765 

32 POSTOPERATIVE CARE, 782 

APPENDIX A DENTAL MATERIALS AND EQUIPMENT 
INDEX, 818 

APPENDIX B MANUFACTURERS' INDEX, 826 



XI 



E C T I O N 



O N 



AND 



i 



CHAPTER 



ONE 



iSTORY Taking 
And Clinical Examination 



chief complaint 

click 

communication 

dental history 

fixed prosthodontics 

fremitus 

medical history 



palpation 

percussion 

periodontal evaluation 

slide 

systemic conditions 

TMJ dysfunction 



Fixed prosthodontic treatment involves the replace- 
ment and restoration of teeth by artificial substitutes 
that are not readily removable from the mouth. Its 
focus is to restore function, esthetics, and comfort. 



Fixed prosthodontics can offer exceptional satisfac- 
tion for both patient and dentist. It can transform an 
unhealthy, unattractive dentition with poor func- 
tion into a comfortable, healthy occlusion capable of 
years of further service while greatly enhancing es- 
thetics (Fig. 1-1, A, B). Treatment can range from the 
fairly straightforward restoration of a single tooth 
with a cast crown (Fig. 1-1, C), replacement of one or 
more missing teeth with a fixed partial denture (Fig. 
1-1, D), to a highly complex restoration involving all 
the teeth in an entire arch or dentition. 

To achieve predictable success in this technically 
exacting and demanding field, there must be meticu- 
lous attention to every detail-from the initial patient 




Fig- 1- 1 - A se. erely damaged maxillary dentition (A) restored with metal-ceramic fixed prostheses 
(B). C, Complete cast crown restores mandibular molar. D, Three-unit fixed partial denture replacing 
missing mandibular premolar. 

(C courtesy Dr. X Lepe. D courtesy Dr. J. Nelson) 



Chapter 1 History Taking and Clinical Examination 



I 



interview and diagnosis, through the active treat- 
ment phases, and to a planned schedule of follow-up 
care. Otherwise, the result is likely to be unsatisfac- 
tory and frustrating for both dentist and patient, re- 
sulting in disappointment and loss of confidence. 

Problems encountered during or following treat- 
ment can often be traced to errors and omissions 
during history taking and initial examination. An 
inexperienced clinician may plunge into the treat- 
ment phase before collecting sufficient diagnostic 
information that will help predict likely pitfalls. 

Making the correct diagnosis is prerequisite to for- 
mulating an appropriate treatment plan. This requires 
that all pertinent information be obtained. A complete 
history includes a comprehensive assessment of the 
patient's general and dental health, individual needs, 
preferences, and personal circumstances. This chapter 
reviews fundamentals of history taking and clinical 
examination, with special emphasis on obtaining the 
necessary information to make appropriate fixed 
prosthodontic treatment decisions. 

^HISTORY 

A patient's history should include all pertinent 
information concerning the reasons for seeking 
treatment, along with any personal information, in- 
cluding relevant previous medical and dental expe- 
riences. The chief complaint should be recorded, 
preferably in the patient's own words. A screening 
questionnaire (Fig. 1-2) is useful for history taking; 
it should be reviewed in the patient's presence to 
correct any mistakes and to clarify inconclusive en- 
tries. If the patient is mentally impaired or a minor, 
the guardian or responsible parent must be present. 

CHIEF COMPLAINT 

The accuracy and significance of the patient's pri- 
mary reason(s) for seeking treatment should be an- 
alyzed first. This may be just the tip of the iceberg, 
and careful examination will often reveal problems 
and disease of which the patient is unaware; never- 
theless, the patient perceives the chief complaint as 
the major problem. Therefore, when a comprehen- 
sive treatment plan is proposed, special attention 
must be given to how it can be resolved. The inex- 
perienced clinician trying to prescribe an "ideal" 
treatment plan can lose sight of the patient's wishes. 
The patient may then become frustrated because the 
dentist apparently does not understand or does not 
want to understand. 

Chief complaints usually fall into one of the fol- 
lowing four categories: 

• Comfort (pain, sensitivity, swelling) 

• Function (difficulty in mastication or speech) 



• Social (bad taste or odor) 

• Appearance (fractured or unattractive teeth or 
restorations, discoloration) 

Comfort. If pain is present, its location, charac- 
ter, severity, and frequency should be noted, as well 
as the first time it occurred, what factors precipitate 
it (e.g., hot, cold, or sweet things), and any changes 
in its character. Is it localized or more diffuse in na- 
ture? It is often helpful to have the patient point at 
the area while paying close attention. 

If swelling is present, the location, size, consis- 
tency, and color are noted as well as how long it has 
been felt and whether it is increasing or decreasing. 

Function. Difficulties in chewing may result 
from a local problem such as a fractured cusp or 
missing teeth; it may also indicate a more general- 
ized malocclusion or dysfunction. 

Social. A bad taste or smell often indicates com- 
promised oral hygiene and periodontal disease. Often 
social pressures prompt the individual to seek care. 

Appearance. Compromised appearance is a 
strong motivating factor for patients to seek advice 
as to whether improvement is possible (Fig. 1-3). 
Such individuals may have missing or crowded 
teeth, or a tooth or restoration may be fractured. 
Their teeth may be unattractively shaped, malposi- 
tioned, or discolored, or there may be a develop- 
mental defect. 

PERSONAL DETAILS 

The patient's name, address, phone number, sex, oc- 
cupation, work schedule, and marital and financial 
status are noted. Much can be learned in a 5-minute, 
casual conversation during the initial visit. In addi- 
tion to establishing rapport and developing a basis 
for the patient to trust the dentist, small and seem- 
ingly unimportant personal details often have con- 
siderable impact on establishing a correct diagnosis, 
prognosis, and treatment plan. 

MEDICAL HISTORY 

An accurate and current general medical history 
should include any medication the patient is taking 
as well as all relevant medical conditions. If neces- 
sary, the patient's physician(s) can be contacted for 
clarification. The following classification may be 
helpful: 

1. Conditions affecting the treatment methodol- 
ogy (e.g., any disorders that necessitate the use 
of antibiotic premedication, any use of steroids 
or anticoagulants, and any previous allergic 



HEALTH QUESTIONNAIRE 



REG. NO. 



Name 



Date 



Age 



Write Yes or No. 



1 . Have you been botspittitized of under the care of a physkian within the last 2 years? 

2. Has there Iseen a change in your general health within the past 2 years? 



z, nas mere rseen acnange m your general neaiin \ 
3. Are you aflergic to p<>rricillin or any other druj*sf 



4. Indicate Ye* or No Id .my of the tonctitions Iselow ibr which you are being treated or you have had: 



Y / N He.3rl aH,itk 

Y / N Heart trouble 

Y / N Heart surgefy 

Y / N Angina (< ho^t pain) 

Y / N High bUxxl pressure 

Y / N Prolapsed niitrai vaJve 

Y y N hiearl murmur 

Y / N Artifittal heart valves 

Y / N Congenital heart lesions 

Y / N CardifK piJcemaker 

Y / N Rheumntit fever 

Y / N Stroke 

Y / N Allergies 

Do you use tobacco? Y / N Type , 
Do you drink alcohol? Y / N Type , 



Y / N Hives, skin rash 

Y / N Cancer treatment 

Y / N Radiation therapy 

Y / N Ulcers 

Y / N Gastritis 

Y / N Hiatus hernia 

Y / N Easy bruisinfi 

Y / N Excessive bleeding 

Y / N Artificial |oim 

Y / N Arthritis 

Y / N Asthma 

Y y N Persistent tough 

Y / N Emphysema 



How much if , 
How much? 



5. Have you had any serious illness, disease, or condition not listed above? 
If so, explain 



Y / N 

Y / N 

Y / N 

Y / N 

Y / N 

Y y N 

Y y N 

Y/N 

Y/ N 

Y / N 

Y / N 



Sulmance abuse 

AIDS 

HtV infection 

Diabetes 

Hepatitis 

Kidney trouble 

Psychiatric ireatmenf 

Fainting spells 

Seizures 

Epilepsy 

Anemia 



Women Only 

Y y N 

Y / N 



Currently pregnant 
Nursing 



Y y N Femjie prolslems 



d. Indicate date of your last physical eiicamination 
7. Name and address of your persortal physician 



n. List any nwdi cations you are currently taking 



S, Have you had ar*y problems or .sHxiety asiociated with previous dental care? 
If so, explain 



DENTAL QUESTIONNAIRE 
indicate Yes or No to the Following: 

Y y N 1G. Does il hurl when you thew? 

Y y N 11 . Is a tooth sensitive or ttmder^ 

Y/N 12. Do you have frequent loolhaches or jjum pain^ 

Y/N 1 ^ Do your gum^ bleeti a loi when you i)rush your tei^ih? 

Y/N M. Do you have occasional dryness or burning in your mouth? 

Y/N 15. Do you have occasional pain in Ihc jaws, ne<k, or temples? 

Y/N U). Does it hurt when you open wide or lake a bi^j bite? 

Y/N 17. Does your jaw make "clicking or popping" sounds when you chew or move your jaw? 

Y / N ia. Do you suffer frofti headache?;? 

Y/N 1*1. Do you have occasional ear pjtn or pain in front of the eai^? 

Y / N 20. Does your jaw "feel tirt'd" after a medl? 

Y/N 21. Do you ever have to search for a place to close your teeth? 
Y/N 22. Does a looth ever get in (be way? 

23. Is there anything you wish to tell us that has not been asked? 

24. Were there any Hems you did not understand? 

I will inform the Clinic of any changes in the aiwve 

Person completing form litgn here: , 



Date Signed: 



self parent 

Circle Relationship 
If Minor: Parent or legal Guardian Signature 



guardian 



Fig. 1-2. Screening questionnaire. 



Chapter 1 History Taking and Clinical Examination 



I 



responses to medication or dental materials). 
Once these are identified, treatment usually can 
be modified as part of the comprehensive treat- 
ment plan, although some factors may severely 
limit available options. 
2. Conditions affecting the treatment plan (e.g., 
previous radiation therapy, hemorrhagic disor- 
ders, extremes of age, and terminal illness). 
These can be expected to modify the patient's 
response to dental treatment and may affect 




Fig. 1 -3. Poor appearance is a common reason for seek- 
ing restorative dental treatment. 



the prognosis. For instance, patients who have 
previously received radiation treatment in the 
area of a planned extraction require special 
measures (hyperbaric oxygen) to prevent seri- 
ous complications. 
3. Systemic conditions with oral manifestations. 
For example, periodontitis may be modified by 
diabetes, menopause, pregnancy, or the use of 
anticonvulsant drugs (Fig. 1-4); in cases of hiatal 
hernia, bulimia, or anorexia nervosa, teeth 
may be eroded by regurgitated stomach acid 1/2 
(Fig. 1-5); certain drugs may generate side 




Fig. 1-4. Severe gingival hyperplasia associated with an- 
ticonvulsant drug use. 

(Courtesy Dr. P.B. Robinson.) 




H 




Fig. 1-5. A, Extensive damage caused 
by self-induced acid regurgitation. Note 
that the lingual surfaces are bare of 
enamel except for a narrow band at the 
gingival. B, Teeth prepared for partial- 
coverage restorations. C, Working cast. 
D and E, The completed restoration. 



I 



Section 1 Planning and Preparation 



effects that mimic temporomandibular disor- 
ders (TMDs)3 or reduce salivary flow.4 .5 

4. Possible risk factors to the dentist and auxiliary 
personnel (e.g., patients who are suspected or 
confirmed carriers of hepatitis B, acquired im- 
munodeficiency syndrome, or syphilis). 
Dental offices practice "universal precautions" to 

ensure appropriate infection control. This means 

that full infection control is taken for every patient; 

no additional measures are needed when treating 

known carriers. 6 

DENTAL HISTORY 

Clinicians should be cautious when commenting 
before a thorough examination is completed. With 
adequate experience, a clinician can often assess 
preliminary treatment needs during the initial ap- 
pointment. However, fairly assessing the quality of 
a previously rendered treatment can be difficult, be- 
cause the circumstances under which the treatment 
was rendered are seldom known. When such an as- 
sessment is requested for legal proceedings, the pa- 
tient should be referred to a specialist familiar with 
the "usual and customary" standard of care. 

Periodontal History. The patient's oral hygiene 
is assessed, and current plaque -control measures 
are discussed, as are previously received oral hy- 
giene instructions. The frequency of any previous 
debridements should be recorded, and the dates 
and nature of any previous periodontal surgery 
should be noted. 

Restorative History. The patient's restorative 
history may include only simple composite resin or 
dental amalgam fillings, or it may involve crowns and 
extensive fixed partial dentures. The age of existing 
restorations can help establish the prognosis and 
probable longevity of any future fixed prostheses. 

Endodontic History. Patients often forget 
which teeth have been endodontically treated. 
These can be readily identified with radiographs. 
The findings should be reviewed periodically so 
that periapical health can be monitored and any re- 
curring lesions promptly detected (Fig. 1-6). 

Orthodontic History. Occlusal analysis should 
be an integral part of the assessment of a postortho- 
dontic dentition. If restorative treatment needs are 
anticipated, they should be undertaken by the 
restorative dentist. Occlusal adjustment (reshaping 
of the occlusal surfaces of the teeth) may be needed 
to promote long-term positional stability of the 
teeth and reduce or eliminate parafunctional activ- 




Fig. 1-6. Defective endodontics has led to recurrence of 
a periapical lesion. Retreatment will be required. 




Fig. 1-7. Apical root resorption subsequent to orthodon- 
tic treatment. 



ity. On occasion, root resorption (detected on radio- 
graphs) (Fig. 1-7) may be attributable to previous 
orthodontic treatment. As the crown/root ratio is 
affected, future prosthodontic treatment and its 
prognosis may also be affected. Restorative treat- 
ment can often be simplified by minor tooth move- 
ment. When a patient is contemplating orthodontic 
treatment, considerable time can be saved if minor 
tooth movement (for restorative reasons) is incorpo- 
rated from the start. Thus good communication be- 
tween the restorative dentist and the orthodontist 
may prove very helpful. 

Removable Prosthodontic History. The pa- 
tient's experiences with removable prostheses must 
be carefully evaluated. For example, a removable 
partial denture may not have been worn for a vari- 
ety of reasons, and the patient may not even have 



Chapter 1 History Taking and Clinical Rxamination 



I 



mentioned its existence. Careful questioning and 
examination will usually elicit discussion concern- 
ing any such devices. Listening to the patient's com- 
ments about previously unsuccessful removable 
prostheses can be very helpful in assessing whether 
future treatment will be more successful. 

Oral Surgical History. Information about miss- 
ing teeth and any complications that may have oc- 
curred during tooth removal is obtained. Special 
evaluation and data collection procedures are nec- 
essary for patients who require prosthodontic care 
subsequent to orthognathic surgery. Before any 
treatment is undertaken, the prosthodontic compo- 
nent of the proposed treatment should be fully co- 
ordinated with the surgical component. 

Radiographic History. Previous radiographs 
may prove helpful in judging the progress of dental 
disease. They should be obtained if possible, be- 
cause it is generally better to avoid exposing the pa- 
tient to unnecessary ionizing radiation. Dental prac- 
tices will usually forward radiographs or acceptable 
duplicates promptly upon request. In most in- 
stances, however, a current diagnostic radiographic 
series is essential and should be obtained as part of 
the examination. 

TMJ Dysfunction History. A history of pain or 
clicking in the temporomandibular joints or neuro- 
muscular symptoms, such as tenderness to palpa- 
tion, may be due to TMJ dysfunction, which 

should normally be treated and resolved before 
fixed prosthodontic treatment begins. A screening 
questionnaire will efficiently identify these prob- 
lems. The patient should be questioned regarding 
any previous treatment for joint dysfunction (e.g., 
occlusal devices, medications, biofeedback, or phys- 
ical therapy exercises). 

^ EXAMINATION 

An examination consists of the clinician's use of 
sight, touch, and hearing to detect conditions out- 
side the normal range. To avoid mistakes, it is criti- 
cal to record what is actually observed rather than 
to make diagnostic comments about the condition. 
For example, "swelling," "redness," and "bleeding 
on probing of gingival tissue" should be recorded 
rather than "gingival inflammation" (which implies 
a diagnosis). 

Thorough examination and data collection are 
needed for the prospective fixed prosthodontic pa- 
tient, and the protocol for this effort can be obtained 
from various textbooks of oral diagnosis.7 .8 



GENERAL EXAMINATION 

The patient's general appearance, gait, and weight 
are assessed. Skin color is noted for signs of anemia 
or jaundice. Vital signs, such as respiration, pulse, 
temperature, and blood pressure, are measured and 
recorded. Fixed prosthodontic treatment is often in- 
dicated in middle-aged or older patients, who can 
be at higher risk for cardiovascular disease. Rela- 
tively inexpensive cardiac monitoring units are 
available for in-office use (Fig. 1-8). Patients with vi- 
tal signs outside normal ranges should be referred 
for a comprehensive medical evaluation before de- 
finitive treatment is initiated. 

EXTRAORAL EXAMINATION 

Special attention is given to facial asymmetry because 
small deviations from normal may hint at serious un- 
derlying conditions. Cervical lymph nodes are pal- 
pated, as are the TMJs and the muscles of mastication. 

Temporomandibular Joints. The clinician lo- 
cates the TMJs by palpating bilaterally just anterior 
to the auricular tragi while having the patient open 
and close. This permits a comparison between the 
relative timing of left and right condylar move- 
ments during the opening stroke. Asynchronous 
movement may indicate an anterior disk displace- 
ment that prevents one of the condyles from making 
a normal translatory movement (see Chapter 4). Au- 
ricular palpation (Fig. 1-9) with light anterior pres- 
sure helps identify potential disorders in the poste- 
rior attachment of the disk. Tenderness, or pain on 
movement, is noted and can be indicative of inflam- 
matory changes in the retrodiscal tissues, which are 
highly vascular and innervated. Clicking in the TMJ 
is often noticeable through auricular palpation but 
may be difficult to detect when palpating directly 
over the lateral pole of the condylar process, be- 
cause the overlying tissues can "muffle" the click. 
Placement of the fingertips on the angles of the 
mandible will help identify even a minimal click, 
because very little soft tissue lies between the fin- 
gertips and the mandibular bone. 

A maximum mandibular opening resulting in 
less than 35 mm of interincisal movement is consid- 
ered to be restricted, because the average opening is 
greater than 50 mm. 9, 10 Such restricted movement on 
opening can be indicative of intracapsular changes 
in the joints. Similarly, any midline deviation on 
opening and/or closing is recorded. The maximum 
lateral movements of the patient can be measured 
(normal is about 12 mm) (Fig. 1-10). 

Muscles of Mastication. Next, the masseter 
and temporal muscles, as well as other relevant 




Section 1 Planning and Preparation 

Ch^rHacteristic'H of the [lulse- 




Regulcir 
1 



R.Kl' 



Rhythm 



Irregular 



Pattern 



H '— j^ 


-1- ^ J- 


' .t ' ^. ^1 


Ji /ill A /\ A 


rTrlir T /iMlVrHTl 1 




"; \i 'j :: 


^ ^h -^ 1- 


- — i- — ■ ■ ■ ■ ' > — . — ~ -J ^ .. i .^_-. 



Fig. 1-8. Cardiac monitoring printout. 
(Courtesy Dr. T. Quilitz.) 



Fast __ 
>1(MVmin 



Normal 



*j{J-iO0/mm 

Slow 

<bO/min 



Early beats 



Skipped beats —— 
Regularly irreguLir 
Totally irregular — 



Common ECC tindings 

Sinus tachycardia 
Venffjcular tachycardia 
Normal sinus rhythm 
Sinus bfadyycarditi 
Heart bfock 

-| Atrial premature contfaction 



-j Premature ventricular contraction 
-\ Sinus arrhythmia 



-| Atrial fibril lation 




\ A 



Fig. 1 -9. Auricular palpation of the posterior aspects of 
the temporomandibular joints. 




Fig. 1 -1 0. Maximum opening of more than 50 mm (A) 
and lateral movement of about 12 mm (B) are normal. 



postural muscles, are palpated for signs of tender- 
ness (Fig. 1-11). Palpation is best accomplished bi- 
laterally and simultaneously. This allows the patient 
to compare and report any differences between the 
left and right sides. Light pressure should be used 
(the amount of pressure one can tolerate when gen- 
tly pushing on one's closed eyelid without feeling 
discomfort is a good comparative measure), and if 



any difference is reported between the left and right 
sides, the patient is asked to classify the discomfort 
as mild, moderate, or severe. If there is evidence of 
significant asynchronous movement or TMJ dys- 
function, a systematic sequence for comprehensive 
muscle palpation should be followed as described 
by Solberg9 and Krogh-Poulsen and Olsson." Each 
palpation site is given a numerical score based on 



Chapter 1 History Taking and Clinical Examination 



I 




the patient's response. If neuromuscular or TMJ 
treatment is initiated, the examiner can then repal- 
pate the same sites periodically to assess the re- 
sponse to treatment (Fig. 1-12). 

Lips. The patient is observed for tooth visibility 
during normal and exaggerated smiling. This can be 
critical in fixed prosthodontic treatment planning, 12 
especially for margin placement of certain metal- 
ceramic crowns. Some patients show only their 
maxillary teeth during smiling. More than 25% do 
not show the gingival third of the maxillary central 
incisors during an exaggerated smile 13 (Fig. 1-13). 
The extent of the smile will depend on the length 
and mobility of the upper lip and the length of the 
alveolar process. When the patient laughs, the jaws 
open slightly and a dark space is often visible 
between the maxillary and mandibular teeth (Fig. 
1-14). This has been called the negative space. ^^ Miss- 
ing teeth, diastemas, and fractured or poorly re- 
stored teeth will disrupt the harmony of the nega- 
tive space and often require correction." 

INTRAORAL EXAMINATION 

The intraoral examination can reveal considerable 
information concerning the condition of the soft tis- 



Fig. 1-11. Muscle palpation. 
A, The masseter. B, The temporal. 
C, The trapezius. D, The sterno- 
cleidomastoid. E, The floor of the 
mouth. 

sues, teeth, and supporting structures. The tongue, 
floor of the mouth, vestibule, cheeks, and hard and 
soft palates are examined, and any abnormalities 
are noted. This information can be properly evalu- 
ated during treatment planning only if objective in- 
dices, rather than vague assessments, are used. 

Periodontal Examination 

Robert F. Bairn a 

A periodontal examination should provide informa- 
tion regarding the status of bacterial accumulation, 
the response of the host tissues, and the degree of ir- 
reversible damage. Because long-term periodontal 
health is essential to successful fixed prosthodontics 
(see Chapter 5), existing periodontal disease must 
be corrected before any definitive prosthodontic 
treatment is undertaken. 

Gingiva. The gingiva should be lightly dried 
before examination so that moisture does not ob- 
scure subtle changes or detail. Color, texture, size, 
contour, consistency, and position are noted and 
recorded. The gingiva is then carefully palpated to 
express any exudate or pus that may be present in 
the sulcular area. 



I 



section 1 Planning and Preparation 

n 





Palpation is btst done 
bilaterally, simultaneously 
asking the patient to 
identity any differences 
between left and right. 



Fig. 1-12. Palpation sites for assessing muscle tenderness. A, TMJ capsule: lateral and dorsal. B, Mas- 

seter: deep and superficial. C, Temporal: anterior and posterior. D, Vertex. E, Neck: nape and base. 

F, Stern ocleidomastoid: insertion, body, and origin. G, Medial pterygoid. H, Posterior digastric. 

1, Temporal tendon. J, Lateral pterygoid. 

(From Ki h-Pouf N WG, Olsson A: Dent Clin North Am 10:627, 1966.) 




Fig. 1 -1 3. Smile analysis is an important part of the examination, particularly when anterior crowns 
or FPDs are being considered. A, Some individuals show considerable gingival tissue during an exagger- 
ated smile. B, Others may not show the gingival margins of even the central incisors. 



spaces. Any deviation from these findings should be 
noted. With the development of chronic marginal 
gingivitis (Fig. 1-15, B), the gingiva becomes en- 
larged and bulbous, loss of stippling occurs, the 
margins and papillae are blunted, and bleeding and 
exudate are observed. 

The width of the band of attached keratinized 
gingiva around each tooth may be assessed by mea- 
suring the surface band of keratinized tissue in an 
apicocoronal dimension with a periodontal probe 
and subtracting the measurement of the sulcus 
depth. Another method to obtain this measurement 
by visual examination is to gently depress the mar- 
ginal gingiva with the side of a periodontal probe or 
explorer. At the mucogingival junction (MGJ), the 
effect of the instrument will be seen to end abruptly, 
indicating the transition from tightly bound gingiva 
to more flexible mucosa. Injecting anesthetic solu- 




Fig. 1 -1 4. The "negative" space between the maxillary 
and mandibular teeth is assessed during the examination. 



Healthy gingiva (Fig. 1-15, A) is pink, stippled, 
and firmly bound to the underlying connective tis- 
sue. The gingival margin is knife-edged, and 
sharply pointed papillae fill the interproximal 



Chapter 1 History Taking and Clinical Examination 





Fig. 1-15. A, Healthy gingivae-pink, knife-edged, and firmly attached. B, Gingivitis-plaque and 
calculus have caused marginal inflammation, with changes in color, contour, and consistency of the free 
gingival margin. Inflammation extends into the keratinized attached gingiva. 




Fig. 1-1 6. A, Three types of sulcus/pocket-measuring probes. B, Correct position of a periodontal 
probe in the interproximal sulcular area, parallel to the root surface and in a vertical direction as far in- 
terproximally as possible. 



tion into the nonkeratinized mucosa close to the 
MGJ to make the mucosa balloon slightly is a third 
method of visualizing the MGJ. However, this is 
done only if the other methods do not provide the 
desired information. 

Periodontium. The periodontal probe (Fig. 
1-16, A) is one of the most reliable and useful 
diagnostic tools available for examining the peri- 
odontium. It provides a measurement (in millime- 
ters) of the depth of periodontal pockets and 
healthy gingival sulci on all surfaces of each tooth. 
In this examination the probe is inserted essentially 
parallel to the tooth and is "walked" circumferen- 
tially through the sulcus in firm but gentle steps, de- 
termining the measurement when the probe is in 
contact with the apical portion of the sulcus (Fig. 1- 
16, B). Thus any sudden change in the attachment 
level can be detected. The probe may also be angled 
slightly (5 to 10 degrees) in the interproximal areas 
to reveal the topography of an existing lesion. Prob- 
ing depths (usually six per tooth) are recorded on a 
periodontal chart (Fig. 1-17), which also contains 
other data pertinent to the periodontal examination 
(e.g., tooth mobility or malposition, open or defi- 
cient contact areas, inconsistent marginal ridge 
heights, missing or impacted teeth, areas of inade- 
quate attached keratinized gingiva, gingival reces- 



sion, furcation involvements, and malpositioned 
frenum attachments). 

CLINICAL ATTACHMENT LEVEL 

Documenting the level of attachment helps the clin- 
ician determine the amount of periodontal destruc- 
tion that has occurred and is essential when render- 
ing a diagnosis of periodontitis (loss of connective 
tissue attachment) 16,17 This measurement also pro- 
vides the clinician with more detailed and accurate 
information regarding the prognosis of an individ- 
ual tooth. The clinical attachment level (CAL or AL) 
is determined by measuring the distance between 
the apical extent of the probing depth and a fixed 
reference point on the tooth, most commonly either 
the apical extent of a restoration and/or the cemen- 
toenamel junction (CEJ). This measurement can be 
documented on modified periodontal charts (Fig. 
1-18) and incorporated with the standard periodon- 
tal documentation (see Fig. 1-17) to complete the 
clinical periodontal examination. When the free 
margin of the gingiva is located on the clinical 
crown and the level of the epithelial attachment is at 
the CEJ, there is no loss of attachment, and recession 
is noted as a negative number. When the level of 
the epithelial attachment is on root structure and 
the free margin of the gingiva is at the CEJ, the at- 
tachment loss equals the probing depth, and the 



■ 



Section 1 Planning and Preparation 



Charting of condition! before periodontal; treatmeni 
Photographs, date Radiographs, date . 

OCCLUSAL 



Casts, dale 



LINGUAL 



FACIAL 



FACIAL 



LINGUAL 




>■ 
a: 
< 



X 

< 



RIGHT 



LEFT 



OCCLUSAL 




< 

—I 

03 



r^ Q 



Fig, 1-17. Chart tor record irij^ picket depths. The parallel lines are approximately 2 mm apart. Fol- 
lowing are the notaHons involved in using the chart: 

1. Block out any missing teeth, 

2. Draw a red X through the crown of any tcHith that is to be extracted. 

3. Record the gingival level with a continuous blue line. 

4. Record pocket depths with a red line interrupted at Ihe proximal surfaces of each tooth. 

5. Shade the pocket form on each tooth with a red pencil (between the red and blue lines). 

6. Indicate bifurcation or tril'urcation involvements with a small red X at the involved area. 

7. Record open contacts with vertical parallel lines ( II ) through the area. 

8. Record improper contacts with a wavy red line (^_) through the area, 

9. Record gingival overhang(s) with a red spur (a) through the area. 

10. Outline cavities and faulty restorations of periodontal significance in red. 

11, Indicate rotated teeth by outlining in blue to show ihfir actual position. 

(Moiiified slight h/ from Coldnian IIM. Cohen DW: Periodontal therapy cd 5, St Louis, 197X Mosby.) 



recession is 0. In a situation in which there is in- 
creased periodontal destruction and recession, the 
loss of attachment measurement equals the probing 
depth plus the measurement of recession (see Fig. 
1-18, B, C). Clinical attachment loss is a measure of 
periodontal destruction at a site, rather than current 
disease activity, and it may be considered the diag- 
nostic "gold standard" for periodontitis. 19 It should 
be documented in the initial periodontal examina- 
tion.") It is an important consideration in the devel- 
opment of the overall diagnosis, treatment plan. 



and prognosis of the dentition and can be an effec- 
tive research tool. 



Dental Charting 

An accurate charting of the state of the dentition 
will reveal important information about the condi- 
tion of the teeth and will facilitate treatment plan- 
ning. Adequate charting (Fig. 1-19), in addition to 
all periodontal information, must show the pres- 



A 



Chapter 1 History Taking and Clinical Examination 



C 



I 



SSiidcnL rLoniE. 
Piri»d«ibi( C 





1»H7 Iidml AE^mhriiiH SFT I^CV 


U^M,l*Mrf. ] 












r 1 










_[_,!- 





_ 




~i_ _L 



Rtcciuiad. 
AL 

































3^J 



--30'? 



i?p p 



izj: 



^.v-y^ 



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g g, f^ ff f) ^ '3 V' <' c y >? 15 ,«;• fp CH 



6^0©e9 e0@@@ 




-Mlmni Hon <i^ ^n| ivp-r-ti-*. li 







wiWn, I.II.III.U.F^ir 



fc!^ Hill ,«>H»*Tal Wmi ' 



PD 






















AL 













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Fig. 1-18. A, Modified periodontal chart B, Maxillary right sextant of modified periodontal chart 
with areas to record probing depths (PD), recession, and attachment loss (AL). C, Maxillary left sextant 
of modified periodontal chart exhibiting clinical documentation. 

(Courtesy University of Detroit Mercy School of Dentistry, Department of Periodontology and Dental Hygiene). 



ence or absence of teeth, dental caries, restorations, 
wear faceting and abrasions, fractures, malforma- 
tions, and erosions. Missing teeth will often have an 
impact on the position of adjacent teeth (see also the 
section on arch integrity in Chapter 3). Similarly, the 
presence of dental caries on one interproximal sur- 
face should alert the examiner to carefully inspect 
the adjacent proximal wall, even if caries is not ap- 
parent radiographically. The degree and extent of 
caries development over time can have a consider- 
able impact on the eventual prognosis of fixed 
prosthodontic treatment. The condition and type of 
the existing restorations are noted (e.g., amalgam, 
cast gold, composite resin, all-ceramic). Open con- 
tacts and areas where food impaction occurs must 
also be identified. The presence of wear facets is in- 
dicative of sliding contact sustained over time and 
thus may indicate parafunctional activity (see 
Chapter 4). Wear facets are often easier to see on di- 
agnostic casts, however (see Chapter 2), during the 
clinical examination, the location of any observed 
facets is recorded. Fracture lines in teeth may re- 
quire fixed prosthodontic intervention, although 
minor hairline cracks in walls that are not subject to 
excessive loading can often go untreated and sim- 
ply be observed at recall appointments (see Chapter 
32). The location of fractures should be indicated on 
the chart, as should any other abnormalities. 



Occlusal Examination. The initial clinical ex- 
amination starts with the clinician asking the pa- 
tient to make a few simple opening and closing 
movements while carefully observing the opening 
and closing strokes. The objective is to determine to 
what extent the patient's occlusion differs from the 
ideal (see Chapter 4) and how well the patient has 
adapted to this difference. Special attention is given 
to initial contact, tooth alignment, eccentric con- 
tacts, and jaw maneuverability. 

Initial Tooth Contact. The relationship of 
teeth in both centric relation (see Chapter 4) and 
the intercuspal position should be assessed. If all 
teeth come together simultaneously at the end of 
terminal hinge closure, the centric relation posi- 
tion (CR) of the patient is said to coincide with the 
maximum inter cusp ation (MI) (see Chapters 2 
and 4). The patient is guided into a terminal hinge 
closure to detect where initial tooth contact oc- 
curs (see the sections on bimanual manipulation 
and terminal hinge closure in Chapters 2 and 4). 
The clinician should ask the patient to "close 
featherlight" until any of the teeth touch and to 
have the patient help identify where that initial 
contact occurs by asking him or her to point at the 
location. If initial contact occurs between two 
posterior teeth (usually molars), the subsequent 



I 



Section 1 Planning and Pr eparation 




Fig. 1-19. A, An appropriate charting system will designate the location, type, and extent of existing 
restorations and the presence of any disease condition, all of which become part of the permanent pa- 

Continued 



tient record. 



movement from the initial contact to the MI posi- 
tion is carefully observed and its direction noted. 
This is referred to as a slide from CR to ML The 
presence, direction, and estimated magnitude of 



the slide are recorded, and the teeth on which ini- 
tial contact occurs are identified. Any such dis- 
crepancy between CR and MI should be evalu- 
ated in the context of other signs and symptoms 



Chapter 1 History Taking and Clinical Examination 



I 



Jj^Frn* 


U-j 


^1 




-' 




■f ^' ■ :: ' Y^ V "^ ^ ^^P^^H 










Fig. 1 -1 9, cont'd. B, Radiographic findings obtained from a full-mouth series are correlated with the 
clinical findings and noted in the record. C to E, Charting is performed to provide a quick reference to 
conditions in the mouth. The following may be useful: 

1. Amalgam restorations (C) are depicted by an outline drawing blocked in solidly to show the size, 
shape, and location of the restoration. 

2. Tooth-colored restorations (D) are depicted by an outline drawing of the size, shape, and location of the 
restoration. 

3. Gold restorations (E) are depicted by an outline drawing inscribed with diagonal lines to show the size, 
shape, and location of the restoration. 

4. Missing teeth are denoted by a large X on the facial. Ungual, and occlusal diagrams of each tooth that 
is not visible clinically or on radiographs. 

5. Caries is recorded by circling the tooth number located at the apex of the involved tooth and noting the pres- 
ence and location of the cavity in the description column corresponding to the tooth number on the right. 

6. Defective restorations are recorded by circling the tooth number and noting the defect in the descrip- 
tion column. 

(Modified slightly from Sturdevant CM et al: The art and science of operative dentistry, ed 3, st Louis, 1994, 

Mosby.) 



that may be present (e.g., elevated muscle tone 
previously observed during the extraoral exami- 
nation, mobility on the teeth where initial contact 
occurs, wear facets on the teeth involved in the 
slide). 



General Alignment (Fig. 1-20). The teeth are 
evaluated for crowding, rotation, supra-eruption, 
spacing, malocclusion, and vertical and horizontal 
overlap. Teeth adjacent to edentulous spaces often 
have shifted position slightly. Small amounts of 



I 



Section 1 Planning anH Preparation 




Fig. 1 -20. Alignment of the dentition can be assessed in- 
traorally, although diagnostic casts allow a more detailed as- 
sessment. This patient has caries-free teeth in good alignment. 



tooth movement can significantly affect fixed 
prosthodontic treatment. Tipped teeth will affect 
tooth preparation design or in severe cases, may re- 
sult in a need for minor tooth movement before 
restorative treatment. Supra-erupted teeth are often 
overlooked clinically but will often complicate fixed 
partial denture design and fabrication. 

The relative relationship of adjacent teeth to teeth 
requiring fixed prosthodontic treatment is important. 
A tooth may have drifted into the space previously 
occupied by the tooth in need of treatment because a 
large filling was previously lost. Such changes in 
alignment can seriously complicate or preclude fab- 
rication of a cast restoration for the damaged tooth 
and may even necessitate its extraction. 

Lateral and Protrusive Contacts. Excursive 
contacts on posterior teeth may be undesirable un- 
der certain circumstances (see Chapter 4). 

The degree of vertical and horizontal overlap of 
the teeth is noted. When asked, most patients are ca- 
pable of making an unguided protrusive move- 
ment. During this movement, the degree of poste- 
rior disclusion that results from the overlaps of the 
anterior teeth is observed. 

The patient is then guided into lateral excursive 
movements, and the presence or absence of contacts 
on the nonworking side and then the working side 
is noted. Such tooth contact in eccentric movements 
can be verified with a thin Mylar strip (shim stock). 
Any posterior cusps that hold the shim stock will be 
evident (Fig. 1-21). Teeth that are subject to exces- 
sive loading may develop varying degrees of mo- 
bility. Tooth movement (fremitus) should be identi- 
fied by palpation (Fig. 1-22). If a heavy contact is 
suspected, a finger placed against the buccal or 




Fig. 1 -21 . Eccentric tooth contact can be tested with thin 
Mylar shim stock. 




Fig. 1-22. Fremitus (movement on palpation) indicates 
tooth contact during lateral excursions. 



labial surface while the patient lightly taps the teeth 
together will locate fremitus in MI. 

Jaw Maneuverability. The ease with which the 
patient moves the jaw and the way it can be 
guided through hinge closure and excursive move- 
ments should be assessed, since these factors are a 
good guide to neuromuscular and masticatory 
function. If the patient has developed a pattern of 
protective reflexes, manipulating the jaw will be 
difficult. The patient's restricted maneuverability 
is recorded. 



Chapter 1 History Taking and Clinical Examination 



I 




Fig. 1-23. A to C, A full-mouth radiographic survey should enable the dentist to make a detailed as- 
sessment of the morphology of each tooth and its bone support. 



RADIOGRAPHIC EXAMINATION 

Radiographs provide essential information to sup- 
plement the clinical examination. Detailed knowl- 
edge of the extent of bone support and the root mor- 
phology of each standing tooth is essential to 
establishing a comprehensive fixed prosthodontic 
treatment plan. Although radiation exposure guide- 



lines recommend limiting the number of radio- 
graphs to only those that will result in potential 
changes in treatment decisions, a full periapical se- 
ries (Fig. 1-23) is normally required for new patients 
so that a comprehensive fixed prosthodontic treat- 
ment plan can be developed. Patient exposure can 
be minimized by using a technique that provides 



I 



Section 1 Planning and Preparation 



the most information with a minimal need for re- 
peat films and by using appropriate protection. The 
use of digital radiography can further help reduce 
radiation exposure. 

Panoramic films (Fig. 1-24) provide useful infor- 
mation about the presence or absence of teeth. They 
are especially helpful in assessing third molars and 
impactions, evaluating the bone before implant 
placement (see Chapter 13), and screening edentu- 
lous arches for buried root tips. However, they do 
not provide a sufficiently detailed view for assess- 
ing bone support, root morphology, caries, or peri- 
apical pathology. 

Special radiographs may be needed for the as- 
sessment of TMJ disorders. A transcranial exposure 
(Fig. 1-25), with the help of a positioning device, 
will reveal the lateral third of the mandibular 
condyle and can be used to detect structural and po- 
sitional changes. However, interpretation may be 
difficult. 21 More information can be obtained from 
serial tomography, arthrography, 22 CT scanning, 23 




Fig. 1-24 . A panoramic film cannot be substituted for a 
full-mouth series because the image is distorted. Neverthe- 
less, it is very useful for assessing unerupted teeth, screen- 
ing edentulous areas for buried root tips, and evaluating 
the bone before implant placement. 




magnetic resonance imaging (Fig. 1-26), or digi- 
tal subtraction radiography of the joints. 

VITALITY TESTING 

Before any restorative treatment, pulpal health must 
be assessed, usually by measuring the response to 
percussion and thermal or electrical stimulation. A 
diagnosis of nonvitality can be confirmed by 
preparing a test cavity without the administration 
of local anesthetic. Vitality tests, however, assess 
only the afferent nerve supply. Misdiagnosis can oc- 
cur if the nerve supply is damaged but the blood 
supply is intact. Careful inspection of radiographs is 




Fig. 1-25 . A transcranial radiograph shows the lateral 
pole of the mandibular condyle (arrow). 



Fig. 1-26. More sophisticated techniques permit the 
generation of computer-assisted images of clinician- 
determined cross-sections. A, A CT scan. B, An MRI show- 
ing the soft tissue in greater detail. 

(Courtesy Dr. J. Petrie.) 



Chapter 1 History Taking and Clinical Rx a mi nation 



I 



therefore an essential aid in the examination of such 
teeth. 

DIAGNOSIS AND PROGNOSIS 

Not all patients seeking fixed prosthodontic treat- 
ment will present diagnostic problems. Nevertheless, 
diagnostic errors are possible, especially when a pa- 
tient complains of pain or symptoms of occlusal dys- 
function. Treatment may be needed to eliminate ob- 
vious dental caries, to restore a fractured prosthesis, 
or to replace a missing tooth. A logical and systematic 
approach to diagnosis will help avoid mistakes. 

DIFFERENTIAL DIAGNOSIS 

When the history and examination are completed, a 
differential diagnosis is made. The practitioner 
should determine the most likely causes of the ob- 
served condition(s) and record them in order of 
probability. A definitive diagnosis can usually be 
developed after such supporting evidence has been 
assembled. 

A typical diagnosis will condense the informa- 
tion obtained during the clinical history taking and 
examination. For instance, a diagnosis could read as 
follows: 28-year-old male, no significant medical 
history; vital signs normal. Chief complaint: Mesio- 
lingual cusp fracture on tooth # 30. Teeth # 1, # 16, # 
17, # 19, and #32 missing. Patient reports significant 
postoperative discomfort after previous molar ex- 
traction. High smile line. Caries: # 6, mesial; # 12, 
distal; # 20, mesio-occlusal; and # 30, mesio- 
occlusal-distal. Tooth # 8 has received previous 
endodontic treatment. Generalized gingivitis four 
posterior quadrants, with recession noted on teeth # 
23, # 24, and # 25. 5-mm pockets on teeth # 18, # 30, 
and #31. Radiographic evidence of periapical 
pathology tooth # 30. Tooth # 30 tests nonvital. 

This hypothetical scenario summarizes the pa- 
tient's problems, allowing subsequent prioritization 
as a treatment plan is developed (see Chapter 3). In 
this case, the patient's chief complaint likely has a 
longer-term history that has only recently led to 
symptoms the patient could identify, causing him to 
seek care. 

PROGNOSIS 

The prognosis is an estimation of the likely course 
of a disease. It can be difficult to make, but its im- 
portance to patient understanding and successful 
treatment planning must nevertheless be recog- 
nized. The prognosis of dental disorders is influ- 
enced by general factors (age of the patient, lowered 
resistance of the oral environment) and local factors 
(forces applied to a given tooth, access for oral hy- 



giene measures). For example, a young person with 
periodontal disease will have a more guarded prog- 
nosis than an older person with the same disease ex- 
perience. In the younger person, the disease has fol- 
lowed a more virulent course because of the 
generally less-developed systemic resistance; these 
facts should be reflected in treatment planning. 

Fixed prostheses function in a hostile environ- 
ment: the moist oral environment is subject to con- 
stant changes in temperature and acidity and con- 
siderable load fluctuation. A comprehensive clinical 
examination helps identify the likely prognosis. All 
facts and observations are first considered individu- 
ally and then correlated appropriately. 

General Factors. The overall caries rate of the 
patient's dentition indicates future risk to the pa- 
tient if the condition is left untreated. Important 
variables include the patient's understanding 
and comprehension of plaque-control measures as 
well as the physical ability to perform those tasks. 
Systemic problems analyzed in the context of the 
patient's age and overall health provide important 
information. Diabetics are prone to a higher inci- 
dence of periodontal pathology, and special pre- 
cautionary measures may be indicated before treat- 
ment begins. Such conditions also affect the overall 
prognosis. 

Some patients are capable of an extremely high 
bite force, whereas others are not. If an elevated 
muscle tone of hypertrophied elevator muscles is 
identified during the extraoral examination and 
multiple intraoral wear facets are observed, loading 
of the teeth will be considerably higher than in the 
dentition of a frail 90-year-old who tires easily when 
asked to close. Other important factors in determin- 
ing overall prognosis are the history and success of 
previous dental treatments. If a patient's previous 
dental care has been successful over a period of 
many years, a better prognosis can be anticipated 
than when apparently properly fabricated prosthe- 
ses fail or become dislodged within a few years of 
initial placement. 

Local Factors. The observed vertical overlap of 
the anterior teeth has a direct impact on the load 
distribution in the dentition and thus can have an 
impact on the prognosis. In the presence of favor- 
able loading, minor tooth mobility is less of a con- 
cern than in the presence of unfavorable directed or 
high load. Impactions adjacent to a molar that will 
be crowned may pose a serious threat in a younger 
individual in whom additional growth can be antic- 
ipated, but it may be of lesser concern in an older 
individual. 



■ 



Section 1 Planning anH Preparation 



Individual tooth mobility, root angulation, root 
morphology, crown-to-root ratios, and many other 
variables all have an impact on the overall fixed 
prosthodontic prognosis. They will be addressed 
later in this book. 



SUMMARY 

The history and clinical examination must provide 
sufficient data for the practitioner to formulate a 
successful treatment plan. If they are too hastily ac- 
complished, details may be missed that can cause 
significant problems during treatment, when it 
may be difficult or impossible to make corrections. 
Also, the overall outcome and prognosis may be 
adversely affected. In particular, it is critical to de- 
velop a thorough understanding of special patient 
concerns relating to previous care and expectations 
about future treatment. Many problems encoun- 
tered during fixed prosthodontic treatment are di- 
rectly traceable to factors overlooked during the 
initial examination and data collection. A diagno- 
sis is a summation of the observed problems 
and their underlying etiologies. The patient's over- 
all prognosis is influenced by general and local 
factors. 




QLOS^km 



anterior guidance: 1 : the influence of the contacting 
surfaces of anterior teeth on tooth-limiting mandibu- 
lar movements. 2: the influence of the contacting sur- 
faces of the guide pin and anterior guide table on ar- 
ticular movements. 3: the fabrication of a relationship 



of the anterior teeth preventing posterior tooth con- 
tact in all eccentric mandibular movements. 

anterior programming device: an individually fabri- 
cated anterior guide table that allows mandibular 
motion without the influence of tooth contacts and 
facilitates the recording of maxillomandibular rela- 
tionships; also used for deprogramming. 

apex: n, pi apexes: or apices: (1601) 1: the uppermost 
point; the vertex. 2: in dentistry, the anatomic end of 
a tooth root. 

artlirograpliy: n 1: roentgenography of a joint after in- 
jection of an opaque contrast material. 2: in den- 
tistry, a diagnostic technique that entails filling the 
lower, upper, or both joint spaces of the temporo- 
mandibular joint with a contrast agent to enable ra- 
diographic evaluation of the joint and surrounding 
structures; used to diagnose or confirm disk dis- 
placements and perforations. 

articulate: vh {1691) 1: to join together as a joint. 2: the 
relation of contacting surfaces of the teeth or their 
artificial replicas in the maxillae to those in the 
mandible. 

articulate: adj (1586) in speech, to enunciate clearly or 
be clearly spoken. 

auscultation: n (ca, 1828) the process of determining 
the condition of various parts of the body by listen- 
ing to the sounds they emit. 

buccolingual relationship: any position of reference rel- 
ative to the tongue and cheeks. 

centric relation record : a registration of the relation- 
ship of the maxilla to the mandible when the 
mandible is in centric relation. The registration may 
be obtained either intraorally or extraorally. 

centric slide: o^^ the movement of the mandible while 
in centric relation from the initial occlusal contact 
into maximum intercuspation (GPT-4). 

chronic pain: pain marked by long duration or fre- 
quent recurrence. 



Sf^fdif Qiic^iiam 



1. Discuss fhe importance of the chief complaint and its management during examinotion and treatment plan 
presentation. 

2. What is the classification of conditions observed as part of the medico! history? 

3. Describe the vorious areos included when taking a comprehensive dental histary. 

4. What systemic conditions may exhibit oral manifestations that can affect a fixed prosthodontic treatment 
plan? 

5« What is included in a comprehensively conducted exirooral examination? Specify all structures included in 

palpation. 
6* Discuss three criHca! observations that ore pari of a comprehensive periodontal evaluolion. Why are they 

important for fixed prosthodontic evaluation? 
7. What would be recorded as part of an intraoral charting? 
8* Discuss the various types of rodiogrophs available for diagnostic purposes. Whaf are the advontoges and 

limitations of each technique? 
9. Give examples of general and focal foctors that may influence the patient's prognosis. 



Chapter 1 History Taking and Clinical Fxamination 



■ 



click: n (1611) a brief sharp sound; with reference to 
the temporomandibular joint, any bright or sharp 
sound emanating from the joint. 

condylar axis: a hypothetical line through the man- 
dibular condyles around which the mandible may 
rotate. 

condylar hinge position: obs the position of the con- 
dyles of the mandible in the glenoid fossae at which 
hinge axis movement is possible (GPT-4). 

crepitation: n a crackling or grating noise in a joint 
during movement, likened to the throwing of fine 
salt into a fire or rubbing hair between the fingers; 
the noise made by rubbing together the ends of a 
fracture bone. 

deflection: n (1605) 1: a turning aside or off course. 2: a 
continuing eccentric displacement of the mandibu- 
lar midline incisal path symptomatic of restriction 
in movement. 

demineralization: n (ca. 1903) 1: loss of minerals (as 
salts of calcium) from the body. 2: in dentistry, de- 
calcification. 

dental cast: a positive life-size reproduction of a part 
or parts of the oral cavity. 

deprogrammer: n various types of devices or materi- 
als used to alter the proprioceptive mechanism dur- 
ing mandibular closure. 

deviation: n (15c) with respect to movement of the 
mandible, a discursive movement that ends in the 
centered position and is indicative of interference 
during movement. 

disk derangement: an abnormal relationship of the ar- 
ticular disk to the condyle, fossa, and/or eminence. 

diagnostic cast: a life-size reproduction of a part or 
parts of the oral cavity and/or facial structures for 
the purpose of study and treatment planning. 

erosion: n (1541) 1: an eating away; a type of ulcera- 
tion. 2: in dentistry, the progressive loss of tooth 
substance by chemical processes that do not involve 
bacterial action-producing defects that are sharply 
defined, wedge-shaped depressions often in facial 
and cervical areas. 

etiologic factors: the elements or influences that can be 
defined as the cause or reason for a disease or lesion. 

facet: n (1625) a small, planar surface on any hard 
body. Usage: the French spelling of fsiCQiJacette, has 
continued to confuse the profession regarding pro- 
nunciation. 

fixed prosthodontics: the branch of prosthodontics 
concerned with the replacement and/or restoration 
of teeth by artificial substitutes that are not readily 
removed from the mouth. 

forces of mastication: obs the motive force created by 
the dynamic action of the muscles during the phys- 
iologic act of mastication (GPT-4). 

fremitus: n (1879) a vibration perceptible on palpation; 
in dentistry, a vibration palpable when the teeth 
come into contact. 



high lip line: the greatest height to which the inferior 
border of the upper lip is capable of being raised by 
muscle function. 

horizontal overlap: the projection of teeth beyond 
their antagonists in the horizontal plane. 

incisal guidance: 1: the influence of the contacting sur- 
faces of the mandibular and maxillary anterior teeth 
on mandibular movements. 2: the influence of the 
contacting surfaces of the guide pin and guide table 
on articulator movements. 

i nfraocclusion: n malocclusion in which the occluding 
surfaces of teeth are below the normal plane of oc- 
clusion. 

i nitial occlusal contact: the first or initial contact of op- 
posing teeth. 

interocclusal distance: the distance between the oc- 
cluding surfaces of the maxillary and mandibu- 
lar teeth when the mandible is in a specified 
position. 

labioversion: n labial position of a tooth beyond nor- 
mal arch form. 

leaf gauge: a set of blades or leaves of increasing 
thickness used to measure the distance between 
two points or to provide metered separation. 

local etiologic factors: the environmental influences 
that may be implicated in the causation, modifica- 
tion, and/or perpetuation of a disease entity. 

low lip line: 1 : the lowest position of the inferior bor- 
der of the upper lip when it is at rest. 2: the lowest 
position of the superior border of the lower lip dur- 
ing smiling or voluntary retraction. 

mandibular hinge position: obs the position of the man- 
dible in relation to the maxilla at which opening 
and closing movements can be made on the hinge 
axis (GPT-4). 

mandibular trismus: reduced mobility of the mandible 
resulting from tonic contracture of the masticatory 
muscles. 

masticatory force: the force applied by the muscles of 
mastication during chewing. 

muscle spasm: a sudden involuntary contraction of a 
muscle or group of muscles attended by pain and 
interference with function. It differs from muscle 
splinting in that the contraction is sustained even 
when the muscle is at rest and the pain/ dysfunction 
is present with passive and active movements of the 
affected part- also called myospasm. 

muscle splinting: (slang) involuntary contraction (rigid- 
ity) of muscles occurring as a means of avoiding the 
pain caused by movement of the part (resistance 
to passive stretch). The involved muscle(s) relaxes 
at rest. 

musculoskeletal pain: deep, somatic pain that origi- 
nates in skeletal muscles, facial sheaths, and ten- 
dons (myogenous pain); bone and periosteum (os- 
seous pain); joint, joint capsules, and ligaments 
(arthralgic pain); and in soft connective tissues. 



■ 



Section 1 Planning and Preparation 



myofascial trigger point: a tiyperirritable spot, usually 
within a skeletal muscle or in the muscle fascia, that 
is painful on compression and can give rise to char- 
acteristic referred pain, tenderness (secondary hy- 
peralgesia), and autonomic phenomena. 

NMR: acronym for Nuclear Magnetic Resonance; a ra- 
diologic procedure that provides images in any plane 
without radiation or any biologic after-effect by pick- 
ing up signals from resonating hydrogen nuclei. 

nonworking side interference: undesirable contacts of 
the opposing occlusal surfaces on the nonworking 
side. 

occlude: vb occluded; occluding: vt (1597) 1: to bring to- 
gether; to shut. 2: to bring or close the mandibular 
teeth into contact with the maxillary teeth. 

occlusal force: the result of muscular force applied on 
opposing teeth; the force created by the dynamic ac- 
tion of the muscles during the physiologic act of 
mastication; the result of muscular activity applied 
to opposing teeth. 

overhang: n (1864) excess restorative material project- 
ing beyond a cavity or preparation margin. 

palpate: vr palpated; palpating: (1849) to examine by 
touch. 

panoramic radiograph: a radiograph produced by a 
panoramic machine-also called onhopanto graph. 

percussion: n (1544) 1: the act of striking a part with 
sharp blows to help diagnose the condition of the 
underlying parts by means of the sound obtained. 
2: in dentistry, striking a part with short, sharp 
blows as a diagnostic aid in evaluation of a tooth or 
dental implant by the sound obtained. 

periapical: adj relating to tissues surrounding the apex 
of a tooth, including the alveolar bone and peri- 
odontal hgament. 

periradicular: adj around or surrounding a tooth root. 

PFM: acronym for Porcelain Fused to Metal. 

physical elasticity of muscle: obs the physical quality of 
being elastic; (i.e., yielding to active or passive 
physical stretch) (GPT-4). 

preoperative records: obs any record(s) made for the 
purpose of study or treatment planning (gpt-4). 

pretreatment records: any records made for the pur- 
pose of diagnosis, recording of the patient history, 
or treatment planning before therapy. 

prosthetic restoration: obs an artificial replacement for 
an absent part of the human body (gpt-4). 

pulpitis: n inflammation of the dental pulp. 

radiograph: n (1880) an image produced on any sensi- 
tive surface by means of electromagnetic radiation 
other than light; an x-ray photograph. 

radiolucent: permitting the passage of radiant energy 
with relatively little attenuation by absorption. 

radiopaque: (1917) a structure that strongly inhibits 
the passage of radiant energy 



range of motion: the range, measured in degrees of a 
circle, through which a joint can be extended or 
flexed. The range of the opening, lateral, and pro- 
trusive excursions of the temporomandibular joint. 

reciprocal click: a pair of clicks emanating from the 
temporomandibular joint, one of which occurs dur- 
ing opening movements and the other during clos- 
ing movements. 

1 record: vb (14c) 1: to register data relating to specific 

conditions that exist currently or previously 2: to 
register permanently by mechanical means (i.e., jaw 
relationships) 

2 record: n (14c) 1: an official document. 2: a body of 

known or recorded facts about someone or some- 
thing. 

reduced interarch distance: an occluding vertical di- 
mension that results in an excessive interocclusal 
distance when the mandible is in rest position and 
in a reduced interridge distance when the teeth are 
in contact-also called overdosure. 

retruded contact position: that guided occlusal relation- 
ship occurring at the most retruded position of the 
condyles in the joint cavities. A position that may be 
more retruded than the centric relation position. 

reverse articulation: an occlusal relationship in which 
the mandibular teeth are located facial to the oppos- 
ing maxillary teeth; the maxillary buccal cusps are po- 
sitioned in the central fossae of the mandibular teeth. 

root fracture: a microscopic or macroscopic cleavage 
of the root in any direction. 

tinnitus: n (1843) a noise in the ears, often described as 
ringing or roaring. 

tomograph: n a radiograph produced from a machine 
that has the source of radiation moving in one direc- 
tion and the film moving in the opposite direction. 

tomography: n a general term for a technique that pro- 
vides a distinct image of any selected plane through 
the body, while the images of structures that lie 
above and below that plane are blurred. The term 
body -section radiography has been applied to the pro- 
cedure, although the several methods to accomplish 
it have been given distinguishing names. 

torus: n;pl tori: (1563) a smooth, rounded anatomical 
protuberance. 

trigger point: a focus of hyperirritability in tissue, 
which, when palpated, is locally tender and leads to 
heterotopic pain. 

unstrained jaw relation: obs 1: the relation of the 
mandible to the skull when a state of balanced toms 
exists among all the muscles involved 2: any jaw re- 
lation that is attained without undue or unnatural 
force and that causes no undue distortion of the tis- 
sues of the temporomandibular joints (GPT-4). 

xerostomia: n dryness of the mouth from lack of nor- 
mal secretions. 



Chapter 1 History Taking and Clinical Examination 



I 



'ki£>7m.6:HC^S 



1. Bouquot JE, Seime RJ: Bulimia nervosa: dental 

perspectives, Pract Periodont A esthet Dent 9:655, 
1997. 

2. Milosevic A: Eating disorders and the dentist, Br 
Dent J 186:109, 1999. 

3. Cope MR: Metoclopramide-induced masticatory 

muscle spasm, BrDent J 154:335, 1983. 

4. Pajukoski H et al: Salivary flow and composition 
in elderly patients referred to an acute care geri- 
atric ward. Oral Surg 84:265, 1997. 

5. Hunter KD, Wilson WS: The effects of antide- 
pressant drugs on salivary flow and content of 
sodium and potassium ions in human parotid 

saliva, Arch Oral Biol 40:983, 1995. 

6. American Dental Association: Infection control 
recommendations for the dental office and labo- 
ratory, J Am Dent Assoc (Suppl) 1, 1992. 

7. Epstein O et al: Clinical examination, ed 2, St 
Louis, 7997, Mosby. 

8. Little JW et al: Dental management of the 
medically compromised patient, ed 5, St Louis, 

1997, Mosby. 

9. Solberg WK: Occlusion-related pathosis and its 
clinical evaluation. In Clark JW editor: clinical 
dentistry, vol 2, eh 35, Hagerstown, Md, 7976, 
Harper & Row. 

10. PuUinger AG et al: Differences between sexes in 
maximum jaw opening when corrected to body 
size, J OralRehabil 14:291, 1987. 

11. Krogh-Poulsen WG, Olsson A: Occlusal dishar- 
monies and dysfunction of the stomatognathic 
system. Dent Clin North Am 10:627,1966. 

12. Moskowitz ME, Nayyar A: Determinants of den- 
tal esthetics: a rational for smile analysis and 
treatment, Compend Contin Educ Dent 16:1164, 
1995. 

13. Crispin B J, Watson JF: Margin placement of es- 
thetic veneer crowns. 1. Anterior tooth visibility, 
J Prosthet Dent 45:278, 1981. 

14. Lombardi RE: The principles of visual percep- 
tion and their clinical application to denture es- 
thetics, ] Prosthet Dent 29:358, 1973. 



15. Matthews TG: The anatomy of a smile, J Prosthet 
Dent 39:128, 1978. 

16. The American Academy of Periodontology: Epi- 
demiology of periodontal diseases, J Periodontol 
67:935, 1996. 

1 7. The American Academy of Periodontology: 
Guidelines for periodontal therapy, J Periodontol 
69:405,1998. 

18. Carranza FA Jr, Newman MG: Clinical periodon- 
tology, ed 8, Philadelphia, 7996, WB Saunders. 

79. Goodson JM: Selection of suitable indicators of 
periodontitis. In Bader JD, editor: Risk assessment 
in dentistry. Chapel Hill, N.C., 1989, University 
of North Carolina Dental Ecology. 

20. The American Academy of Periodontology: 
Parameters of care, Chicago, 799S, The American 
Academy of Periodontology. 

21. Van Sickels JE et al: Transcranial radiographs in 
the evaluation of craniomandibular (TMJ) disor- 
ders, J Prosthet Dent 49:244, 1983. 

22. Blaschke DD et al: Arthrography of the temporo- 
mandibular joint: review of current status, J Am 
Dent Assoc 100:388, 1980. 

23. Fava C, Preti G: Lateral transcranial radiography 
of temporomandibular joints. 11. Image forma- 
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J Prosthet Dent 59:218, 1988. 

24. Laurell KA et al: Magnetic resonance imaging of 
the temporomandibular joint. I. Literature re- 
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25. Laurell KA et al: Magnetic resonance imaging of 
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findings, ] Prosthet Dent 58:211, 1987. 

26. Laurell KA et al: Magnetic resonance imaging of 
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cephalostat for clinical imaging, J Prosthet Dent 
58:355,1987. 

27. Kapa SF et al: Assessing condylar changes with 
digital subtraction radiography. Oral Surg 
75:247, 1993. 



'^^m 



CHAPTER 






Diagnostic Casts 
AND Related Procedures 




anterior guide table 
arbitrary facebow 
arcon 
articulator 
articulator controls 
centric relation (CR) 
centric relation record 
diagnostic impressions 



diagnostic waxing 
hinge axis 

i rreversible hydrocolloid 
kinematic facebow 
nonarcon 
pantograph 
programming device 
third reference point 



Accurate diagnostic casts (Fig. 2-1) transferred to a 
semiadjustable articulator are essential in planning 
fixed prosthodontic treatment. This permits static 
and dynamic relationships of the teeth to be exam- 
ined without interference from protective neuro- 
muscular reflexes, and unencumbered views from 
all directions reveal aspects of the occlusion not al- 
ways easily detectable intraorally (e.g., the relation- 
ship of the Ungual cusps in the occluded position). If 
the maxillary cast has been transferred with a face- 
bow, a centric relation (CR) interocclusal record has 
been used for articulation of the mandibular cast, 
and the condylar elements have been appropriately 
set (such as with protrusive and/or excursive inte- 
rocclusal records), reproducing the patient's move- 
ments with reasonable accuracy is possible. If the 
casts have been articulated in CR, assessing both the 
CR and the MI position is possible, because any slide 
can then be reproduced. Other critical information 
not immediately apparent during the clinical exami- 
nation includes the occlusocervical dimension of 
edentulous spaces. On an articulator, these are read- 
ily assessed in the occluded position and throughout 
the entire range of mandibular movement. Relative 
alignment and angulation of proposed abutment 
teeth are easier to evaluate on casts than intraorally, 
as are many other subtle changes in individual tooth 
position. Articulated diagnostic casts permit a de- 
tailed analysis of the occlusal plane and the occlu- 
sion, and diagnostic procedures can be performed 
for a better diagnosis and treatment plan; tooth 




Fig. 2- 1 . Diagnostic casts mounted on a Whip Mix 
articulator. 



preparations can be "rehearsed" on the casts, and di- 
agnostic waxing procedures allow evaluation of the 
eventual outcome of proposed treatment. 



IMPRESSION MAKING FOR 
lAGNOSTIC CASTS 

Accurate impressions of both dental arches are re- 
quired. Flaws in the impressions will result in inac- 
curacies in the casts that easily compound. For in- 
stance, a small void in the impression caused by 
trapping an air bubble on one of the occlusal sur- 
faces will result in a nodule on the occlusal table. If 
it is not recognized and carefully removed, it will 
lead to an inaccurate articulator mounting, and the 
diagnostic data will be incorrect. 

As long as the impression extends several mil- 
limeters beyond the cervical line of the teeth, the 
borders of diagnostic impressions are usually not of 
great concern for fixed prosthodontic purposes, un- 
less a removable prosthesis also is to be fabricated. 
Properly manipulated irreversible hydrocolloid (al- 
ginate) is sufficiently accurate and offers adequate 



25 



■ 



Section 1 Planning and Preparation 



surface detail for planning purposes. However, the 
material does not reproduce sufficient surface detail 
for suitable working casts and dies on which actual 
fixed prostheses are fabricated (see Chapter 17). 

Irreversible hydrocolloid 

The irreversible hydrocolloids, or alginates, are es- 
sentially sodium or potassium salts of alginic acid 
and are therefore water soluble. They react chemi- 
cally with calcium sulfate to produce insoluble cal- 
cium alginate. These materials contain other ingre- 
dients, chiefly diatomaceous earth (for strength and 
body), trisodium phosphate (Na3P04), and similar 
compounds to control the setting rate as they react 
preferentially with calcium sulfate. When this reac- 
tion is complete and the retarder is consumed, gel 
formation begins. The clinician can control the reac- 
tion rate by varying the temperature of the mixing 
water. Because set irreversible hydrocolloid is 
largely water, it will readily absorb (by imbibition) 
as well as give off (by syneresis) liquid to the at- 
mosphere, causing distortion of the impression. 
Alginate impressions must therefore be poured 
immediately. 



DIAGNOSTIC IMPRESSION TECHNIQUE 
Armamentarium 

Impression trays 
Modeling compound 
Mixing bowl 
Mixing spatula 
Gauze squares 
Irreversible hydrocolloid 
ADA Type IV or V stone 
Vacuum mixer 
Humidor 
Disinfectant 



Tray Selection 

All impression materials require retention in the im- 
pression tray. This can be provided for irreversible hy- 
drocolloid by using an adhesive or by making perfo- 
rations or undercuts around the rim of the tray. All 
types of trays are capable of producing impressions 
with clinically acceptable accuracy.' For irreversible 
hydrocolloids, the largest tray that will fit comfort- 
ably in the patient's mouth should be selected. A 
greater bulk of material will produce a more accurate 
impression (i.e., a bulky impression has a more favor- 
able surface area/volume ratio and is less susceptible 
to water loss or gain and therefore unwanted dimen- 
sional change). In contrast, elastomeric impression 
materials work well with a relatively tightly fitting 
custom impression tray in which a relatively uniform 
thin layer of material is used. This produces the most 
accurate impression (see Chapter 14). 



Distortion of irreversible hydrocolloid can occur 
if any part of the impression is unsupported by the 
tray or if there is movement of the tray during set- 
ting. For these reasons, the tray may need to be ex- 
tended and its perimeter modified with modeling 
compound (Fig. 2-2). 

Impression Making 

For optimum results the teeth should be cleaned and 
the mouth thoroughly rinsed. Some drying is neces- 
sary, but excessively dried tooth surfaces will cause 
the irreversible hydrocolloid impression material to 
adhere. The material is mixed to a homogeneous 
consistency, loaded into the tray, and its surface 
smoothed with a moistened, gloved finger.' Concur- 
rently, a small amount of material is wiped into the 
crevices of the occlusal surfaces (Fig. 2-3, A, B) before 
the tray is seated (Fig. 2-3, C). Also, a small amount 
can be applied by wiping it into the mucobuccal 
fold. As the tray is inserted into the patient's mouth 
and seated, the patient is reminded to relax the 
cheek muscles. If a patient continues to stretch wide 
open while the tray is being fully seated, impression 
material is often squeezed out of the mucobuccal 
fold or from underneath the upper lip. 

A loss of tackiness of the material (gelation) im- 
plies initial set. The tray should be removed quickly 
2 to 3 minutes after gelation. Teasing or wiggling the 
set impression from the mouth causes excessive dis- 
tortion due to viscous flow. Also, certain irreversible 
hydrocolloid materials distort if held in the mouth 
more than 2 or 3 minutes after gelation. 3 Following 
removal, the impression should be rinsed and disin- 
fected, dried slightly with a gentle air stream, and 
poured immediately. For disinfection, spraying with 




Fig. 2-2. Stock impression trays can be readily modified 
with modeling compound to provide better support for the 
alginate. Typically the posterior border needs extension. If 
the patient has a high palate, the alginate should be sup- 
ported here too, although it should not block out the reten- 
tive area of the tray. 



Chapter 2 Diagnostic Casts and Related Pmrerliirps 



I 



a suitable glutaraldehyde and placement in a self- 
sealing plastic bag for approximately 10 minutes is 
recommended, after which it can be poured. Alter- 
natively, the impression can be immersed in 
iodophor or glutaraldehyde disinfectant. The disin- 
fection protocol is an essential precaution for pre- 
venting cross-infection and protecting laboratory 
personnel (see Chapter 14). It should be noted that 
irreversible hydrocoUoid impressions carry signifi- 
cantly higher numbers of bacteria than elastomeric 
materials.' There is no significant loss of accuracy or 





Fig. 2-3. A to C, Making an alginate impression for diag 
no Stic casts. 



surface detail due to the disinfection procedure. 5,6 To 
ensure accuracy, pouring should be completed 
within 15 minutes of the time the impression is re- 
moved from the mouth. Keeping an impression in a 
moist towel is no substitute for pouring within the 
specified time. Trimming off gross excess impression 
material before setting the tray down on the bench 
top is helpful. A vacuum-mixed ADA Type IV or 
Type V stone is recommended. The choice of the 
brand of stone is important because of the harmful 
surface interactions between specific irreversible hy- 
drocoUoid materials and gypsum products.' 

After mixing, a small amount of stone is added in 
one location (e.g., the posterior aspect of one of the 
molars). Adding small amounts consistently in the 
same location will minimize bubble formation (see 
the section on pouring stone dies in Chapter 17). If air 
is trapped, bubbles can be eliminated by poking at 
them with a small instrument (e.g., a periodontal 
probe or a wax spatula). While setting, the poured 
impressions must be stored tray side down, not in- 
verted. Inverting freshly poured impressions results 
in a cast with a rough and grainy surface.' Stone is 
added to create a sufficient base that provides ade- 
quate retention for mounting on the articulator. To 
achieve maximum strength and surface detail, the 
poured impression should be covered with wet paper 
and stored in a humidor for 1 hour. This minimizes 
distortion of the irreversible hydrocoUoid during the 
setting period. The setting gypsum cast should never 
be immersed in water. If this is done, setting expan- 
sion of plaster, stone, or die stone will double or even 
triple through the phenomenon of hygroscopic ex- 
pansion (see Chapter 22). For best results, the cast 
should be separated 1 hour after pouring. 

Evaluation 

Although it is apparently a simple procedure, diag- 
nostic cast fabrication is often mishandled. Seem- 
ingly minor inaccuracies can lead to serious diag- 
nostic errors. Questionable impressions and casts 
should be discarded and the process repeated (Fig. 
2-4). Voids in the impression create nodules on the 
poured cast. These can prevent proper articulation 
and effectively render useless a subsequent occlusal 
analysis or other diagnostic procedure. 

Articulator Selection 

Handheld casts can provide information concerning 
alignment of the individual arches but do not 
permit analysis of functional relationships. For an 
analysis, the diagnostic casts need to be attached to 
an articulator, a mechanical device that simulates 
mandibular movement. Articulators can simulate 
the movement of the condyles in their corresponding 
fossae. They are classified according to how closely 



I 



Sertion 1 Planning and Preparation 




Fig. 2-4. Diagnostic casts must be accurate if they are to 
articulate properly. A, Occlusal nodules may make proper 
occlusal analysis impossible. B, Proper technique will en- 
sure a satisfactory cast. 

they can reproduce mandibular border movements. 
Because the movements are governed by the bones 
and ligaments of the TMJs, they are relatively con- 
stant and reproducible. Most articulators use me- 
chanically adjustable posterior controls to simulate 
these movements, although some use plastic pre- 
milled or customized fossa analogs. If an articulator 
closely reproduces the actual border movements of 
a given patient, this will significantly reduce chair 
time because the dental laboratory can then design 
the prosthesis to be in functional harmony with the 
patient's movements. In addition, less time will be 
needed for adjustments at delivery. 

On some instruments, the upper and lower mem- 
bers are permanently attached to each other, while on 
others they can be readily separated. The latter group 
may have a latch or clamplike feature that locks the 
two components together in the hinge position. In- 
strument selection depends on the type and complex- 
ity of treatment needs, the demands for procedural 
accuracy, and general expediency. For instance, when 
waxing a fixed partial denture, it is advantageous to 
be able to separate the instrument into two more eas- 
ily handled parts. Use of the proper instrument for a 
given procedure can translate into significant time- 
saving during subsequent stages of treatment. 

SMALL NONADJUSTABLE ARTICULATORS 

Many cast restorations are made on small nonad- 
justable articulators (Fig. 2-5). Their use often leads 




Fig. 2-5. A small nonadjustable articulator. 



to restorations with occlusal discrepancies, because 
these instruments do not have the capacity to repro- 
duce the full range of mandibular movement. Some 
discrepancies can be corrected intraorally, but this is 
often time consuming and frustrating, leading to in- 
creased inaccuracy. If discrepancies are left uncor- 
rected, occlusal interferences and associated neuro- 
muscular disorders may result. 

Of practical significance are differences between 
the hinge closure of a small articulator and that of 
the patient. The distance between the hinge and the 
tooth to be restored is significantly less on most non- 
adjustable articulators than in the patient. This can 
lead to restorations with premature tooth contacts 
because cusp position is affected. This type of arcing 
motion on the nonadjustable articulator results in 
steeper travel than occurs cUnically, resulting in pre- 
mature contacts subsequently on fabricated restora- 
tions between the distal mandibular inchnes and the 
mesial maxillary inclines of posterior teeth (Fig. 2-6). 

Depending on the specific design of the articula- 
tor, ridge and groove direction may be affected in ac- 
cordance with the same principle. This is important 
to note, because resulting prematurities are likely on 
the nonworking side (see Chapters 1 and 4). 

SEMIADJUSTABLE ARTICULATORS 

For most routine fixed prostheses, the use of a semi- 
adjustable articulator (Fig. 2-7) is a practical ap- 
proach to providing the necessary diagnostic infor- 
mation while minimizing the need for clinical 
adjustment during treatment. Semiadjustable in- 
struments do not require an inordinate amount of 
time or expertise. They are about the same size as 
the anatomic structures they represent. Therefore, 
the articulated casts can be positioned with suffi- 
cient accuracy so that arcing errors will be minimal 
and usually of minimal clinical significance (i.e.. 



Chapter 2 Diagnostic Casts and Related Procedures 



I 




The radius o£ the arc of 
closure affects the likeli- 
hood of interferences. 



Fig. 2-6. Discrepancies in the path of closure when using a 
small nonadjustable articulator can lead to restorations with 
premature occlusal contacts. A, Path of closure of an anatomi- 
cally accurate articulator. B, The small nonadjustable instru- 
ment has a smaller radius closure path, which results in pre- 
mature contact at the clinical try-in between the premolars 
during hinge closure. 




.^^ ,♦. .^1^ 





Fig. 2-7. Semiadjustable arcon articulators. A, The Denar Mark 11. B, The Whip Mix model 2240. 
(A Courtesy Dmar Corporation.) 



minimal time should be required for chairside ad- 
justments of fabricated prostheses). 

There are two basic designs of the semiadjustable 
articulator: the arcon (for articulator and condyle) 
(Fig. 2-8, A, C) and the nonarcon (Fig. 2-8, B, D). 
Nonarcon instruments gained considerable popular- 



ity in complete denture prosthodontics because the 
upper and lower members are rigidly attached, per- 
mitting easier control when positioning artificial 
teeth. As a consequence of their design, however, 
certain inaccuracies occur in cast restorations, which 
led to the development of the arcon-type instrument. 



I 



Section 1 Planning and Preparation 




& 



Fig. 2-8. A and C show an arcon; B and D show a nonarcon articulator. An advantage of the arcon 
design is that the condylar inclination of the mechanical fossae is at a fixed angle to the maxillary oc- 
clusal plane. With the nonarcon design, the angle changes as the articulator is opened, which can lead to 
errors when a protrusive record is being used to program the articulator. 

(Redrawn from Shillingburg HT et al: Fundamentals of fixed prOSthodonticS, ed 2, Chicago, 1981, Quintessence 
Publishing. ) 



In an arcon articulator, the condylar spheres are 
attached to the lower component of the articulator, 
and the mechanical fossae are attached to the upper 
member of the instrument. Thus, the arcon articu- 
lator is anatomically "correct," which makes under- 
standing of mandibular movements easier, as 
opposed to the nonarcon articulator (whose move- 
ments are confusingly "backward"). The angulation 
of the mechanical fossae of an arcon instrument is 
fixed relative to the occlusal plane of the maxillary 
cast; in the nonarcon design, it is fixed relative to the 
occlusal plane of the mandibular cast. 

Most semiadjustable articulators permit adjust- 
ments to the condylar inclination and progressive 
and/or immediate side shift. Some have straight 
condylar inclined paths, although more recent 
instruments have curved condylar housings, which 
are more anatomically correct. 

The mechanical fossae on semiadjustable articu- 
lators can be adjusted to mimic the movements of 
the patient through the use of interocclusal 
records. These consist of several thicknesses of 



wax or another suitable material in which the pa- 
tient has closed. Because these records can be sev- 
eral millimeters thick, an error is introduced when 
setting nonarcon articulators with protrusive wax 
records, because its condylar path is not fixed rela- 
tive to the maxillary occlusal plane. As the protru- 
sive record used to adjust the instrument is re- 
moved from the arcon articulator, the maxillary 
occlusal plane and the condylar inclination be- 
come more parallel to each other, leading to re- 
duced cuspal heights in subsequently fabricated 
prostheses (see Table 4-3). 

FULLY ADJUSTABLE ARTICULATORS 

A fully (or highly) adjustable articulator (Fig. 2-9) 
has a wide range of positions and can be set to fol- 
low a patient's border movements. The accuracy of 
reproduction of movement depends on the care and 
skill of the operator, the errors inherent in the artic- 
ulator and recording device, and any malalign- 
ments due to slight flexing of the mandible and the 
nonrigid nature of the TMJs. 




Chapter 2 Diagnostic Casts and Related Proce rlnres; 
^FACEBOWS 



I 



Fig. 2-9. Fully adjustable articulators. A, The Stuart. 
B,TheDenarD5A. 



Rather than relying on wax records to adjust the 
instrument, special pantographic tracings are used to 
record the patient's border movements in a series of 
tracings. The armamentarium used to generate these 
tracings is then transferred to the articulator, and the 
instrument is adjusted so the articulator replicates 
the tracings, essentially reproducing the border 
movements of the patient. The ability of fully ad- 
justable instruments to track irregular pathways of 
movement throughout entire trajectories permits the 
fabrication of complex prostheses, requiring minimal 
adjustment at the try-in and delivery appointment. 

Fully adjustable articulators are not often re- 
quired in general practice. Using and adjusting 
them can be time consuming and requires a high 
level of skill and understanding from the dentist 
and the technician. Once this skill has been ac- 
quired, however, the detailed information they con- 
vey can save considerable chairside time. They can 
be very useful as treatment complexity increases 
(e.g., when all four posterior quadrants are to be re- 
stored simultaneously or when it is necessary to re- 
store an entire dentition, especially in the presence 
of atypical mandibular movement). 



TRANSVERSE HORIZONTAL AXIS 

The mandibular hinging movement around the 
transverse horizontal axis is repeatable. That makes 
this imaginary "hinge axis" around which the 
mandible may rotate in the sagittal plane of consid- 
erable importance when fabricating fixed prosthe- 
ses. Facebows are used to record the anteroposterior 
and mediolateral spatial position of the maxillary 
occlusal surfaces relative to this transverse opening 
and closing axis of the patient's mandible. The face- 
bow is then attached to the articulator to transfer 
the recorded relationship of the maxilla by ensuring 
that the corresponding cast is attached in the correct 
position relative to the hinge axis of the instrument. 
After the maxillary cast has been attached to the ar- 
ticulator with mounting stone or plaster, the 
mandibular cast is subsequently related to the max- 
illary cast through the use of an interocclusal record. 
If the patient's casts are accurately transferred to an 
instrument, considerable time is saved in the fabri- 
cation and delivery of high-quality prostheses. 

Most facebows are rigid, caliper-like devices that 
permit some adjustments. Two types of facebows are 
recognized: arbitrary and kinematic. Arbitrary face- 
bows are less accurate than the kinematic type, but 
they suffice for most routine dental procedures. 
Kinematic facebows are indicated when it is critical 
to precisely reproduce the exact opening and closing 
movement of the patient on the articulator. For in- 
stance, when a decision to alter the vertical dimen- 
sion of occlusion is to be made in the dental labora- 
tory during the fabrication of fixed prostheses, the 
use of a kinematic facebow transfer in conjunction 
with an accurate CR interocclusal record is indicated. 

KINEMATIC HINGE AXIS FACEBOW 

Hinge Axis Recording. The hinge axis of the 
mandible can be determined to within 1 mm by ob- 
serving the movement of kinematic facebow styli po- 
sitioned immediately lateral to the TMJ close to the 
skin. A clutch (Fig. 2-10, A), which is essentially a seg- 
mented impression traylike device, is attached onto 
the mandibular teeth with a suitable rigid material 
such as impression plaster. The kinematic facebow 
consists of three components: a transverse component 
and two adjustable side arms. The transverse rod is at- 
tached to the portion of the clutch that protrudes from 
the patient's mouth. The side arms are then attached to 
the transverse member and adjusted so that the styli 
are as close to the joint area as possible. The mandible 
is then manipulated to produce a terminal hinge 
movement, and the stylus locations are adjusted with 
thumbscrews (superiorly and inferiorly, anteriorly 
and posteriorly) until they make a purely rotational 




Fig. 2-1 0. Kinematic hinge axis facebow. A, Mandibular 
clutch. The clutch separates for removal into two components 
by loosening the screws on left and right sides. B, Transferring 
the position of the mandibular hinge axis. C, pointers aligned 
with the previously marked hinge axis location. D, Kinematic 
facebow aligned on the articulator. 




The locator is adjusted 
properly when the pointer 
remains stationary during 
hinge movement. 



Fig 2-1 1 . Hinge axis recording: Left and right styli are attached via a facebow to a clutch affixed to 
the mandibular teeth. When the mandible makes a strictly rotational movement, the stylus will remain 
stationary if aligned with the actual axis of rotation. If the stylus is positioned forward or backward, 
above or below the actual axis, it will travel one of the arcs indicated by the arrows when the mandible 
makes a rotational movement. Thus, the arc indicates in what direction an adjustment should be made 
to the stylus position. 



Chapter 2 Diagnostic Casts and Related Procedures 



I 



movement (Fig. 2-11). Because the entire assembly is 
rigidly attached to the mandible, a strictly rotational 
movement signifies that stylus position coincides with 
the hinge axis. When this purely rotational movement 
is verified, the position of the hinge axis is marked 
with a dot on the patient's skin, or it may be perma- 
nently tattooed if future use is anticipated or required. 

Kinematic Facebow Transfer. An impression of 
the maxillary cusp tips is obtained in a suitable 
recording medium on a facebow fork. The facebow 
is attached to the protruding arm of the fork. The 
side arms are adjusted until the styli are aligned with 
the hinge axis marks on the patient's skin. The pa- 
tient must be in the same position that was used 
when the axis was marked to prevent skin move- 
ment from introducing any inaccuracy. A pointer de- 
vice is usually attached to the bow and adjusted to a 
repeatable reference point selected by the clinician. 
The reference point is used later for reproducibility. 
The kinematic facebow recording is then transferred 
to the articulator, and the maxillary cast is attached. 

The kinematic facebow technique is time con- 
suming, so it is generally limited to extensive 
prosthodontics, particularly when a change in the 
vertical dimension of occlusion is to be made. A less 
precisely derived transfer would then lead to unac- 
ceptable errors and a compromised result. 

ARBITRARY HINGE AXIS FACEBOW 

Arbitrary hinge axis facebows (Fig. 2-12) approximate 
the horizontal transverse axis and rely on anatomic 
average values. Manufacturers design these facebows 
so the relationship to the true axis falls within an ac- 
ceptable degree of error. Typically, an easily identifi- 
able landmark such as the extemal acoustic meatus is 
used to stabilize the bow, which is aligned with ear- 
pieces similar to those on a stethoscope. Such face- 
bows can be used single-handedly because they are 
self-centering and do not require complicated assem- 
bly. They give a sufficiently accurate relationship for 



most diagnostic and restorative procedures. How- 
ever, regardless of which arbitrary position is chosen, 
a minimum error of 5 mm from the axis can be ex- 
pected. When coupled with the use of a thick inte- 
rocclusal record made at an increased vertical dimen- 
sion, this factor can lead to considerable inaccuracy. 

Anterior Reference Point (Fig. 2-13). The use of 
an anterior reference point enables the clinician to 
duplicate the recorded position on the articulator at 
future appointments. This saves time, because pre- 
viously recorded articulator settings can be used 
again. An anterior reference point, such as the inner 
canthus of the eye or a freckle or mole on the skin, 
is selected. After this has been marked, it is used, 
along with the two points of the hinge axis, to define 
the position of the maxillary cast in space. This has 
the following advantages: 

• After the posterior controls have been adjusted 
initially, subsequent casts can be mounted on 
the articulator without repeating the facebow 
determinations and having to reset the posterior 
articulator controls. 

• Because the maxillary arch is properly posi- 
tioned relative to the axis, average values for 
posterior articulator controls can be used with- 
out having to readjust the instrument on the ba- 
sis of eccentric records. 

• When the articulator has been adjusted, the re- 
sulting numerical values for the settings can be 
compared with known average values to pro- 
vide information about the patient's individual 
variations and the likelihood of encountering 
difficulties during restorative procedures. 

Facebow Transfer 
A rm am entarium 

• Arbitrary-type hinge axis facebow 

• Modeling compound 

• Cotton rolls 




Fig. 2- 1 2. A, The Denar Slidematic and, B, Whip 
Mix Quick Mount arbitrary hinge axis facebows. Note 
the nasion relator as the third reference point. 

(A Courtesy Denar Corporation. ) 



I 



Ser-tion 1 Planning anH Preparation 




Fig. 2-13. A, B, The Denar Slidematic facebow uses a mark 43 mm superior to the incisal edge of the 
maxillary central incisor as an anterior reference point. Other systems use the infraorbital foramen or na- 
sion. The mark serves as a reference to average anatomic values. It also allows subsequent casts to be 
mounted without a repeat recording. 



Step -by -step Procedure 

1. Add modeling compound to the facebow 
fork (Fig. 2-14, A). 

2. Temper in water and seat the fork, making in- 
dentations of the maxillary cusp tips. The 
facebow fork is positioned in the patient's 
mouth, and an impression is made of the 
maxillary cusp tips. The impression must be 
deep enough to permit accurate reposition- 
ing of the maxillary cast after the facebow 
fork has been removed from the mouth. Only 
the cusp tips should be recorded. It is not 
necessary to get an impression of every cusp, 
or even an entire cusp-just one that is suffi- 
cient to position the diagnostic cast accu- 
rately. If the impression is too deep, accurate 
repositioning of the cast can become prob- 
lematic because the diagnostic casts are not 
absolutely accurate reproductions of the 
teeth. In general, the tips are reproduced 
more accurately than the fossae. 

3. Remove the fork from the mouth. Chill and 
reseat the fork, and check that no distortion 
has occurred (Fig. 2-14, B). The inclusion of 
details of pits and fissures in the recording 
medium will lead to inaccuracies when try- 
ing to seat the stone cast. Trim the recording 
medium as necessary before reseating. After 
reseating, check for stability. 

4. Have the patient stabilize the facebow fork by 
biting on cotton rolls. As an alternative, wax 
can be added to the mandibular incisor region 
of the fork. The mandibular anterior teeth will 
stabilize the fork as they engage the wax. 



5. Slide the universal joint onto the fork and po- 
sition the caliper to align with the anterior 
reference mark (Fig. 2-14, C). 

6. Tighten the screws securely in the correct se- 
quence (Fig. 2-14, D). 

7. If the articulator has an adjustable intercon- 
dylar width, record this measurement (Fig. 
2-14, E). Remove the facebow from the mouth. 

The technique is slightly different with other ar- 
bitrary facebows (Fig. 2-14, Fto k). 

Centric Relation Record. A centric relation 
record (Fig. 2-15) provides the orientation of 
mandibular to maxillary teeth in CR in the terminal 
hinge position, where opening and closing are 
purely rotational movements. Centric relation is de- 
fined as the maxillomandibular relationship in 
which the condyles articulate with the thinnest 
avascular portion of their respective disks with the 
condyle-disk complex in the anterior-superior posi- 
tion against the articuaar eminences. This position is 
independent of tooth contact. 

Maximum intercuspation may or may not occur 
coincident with the centric relation position. The 
centric relation record is transferred to the maxillary 
cast on the articulator and is used to relate the 
mandibular cast to the maxillary cast. Once the 
mandibular cast is attached to the articulator with 
mounting stone, the record is removed. The casts 
will then occlude in precisely the CR position as 
long as the maxillary cast is correctly related to the 
hinge axis with a facebow (see Fig. 2-14). When the 
articulator controls are set properly, using appro- 
priate excursive records, translated mandibular 



Chapter 2 Diagnostic Casts and Related PronpHnrps 



I 




w> 






» 



45 55 65 «f 75 85 9 



mm 



H 






Fig. 2-14. Facebow technique: A to E, 
Denar Slide matic Facebow Technique. A, 
Indentations obtained in compound. B, 
Bitefork positioned. C, Facebow attached to 
bitefork, toggles tightened. D, Transfer 
complete. E, Width measurement is read 
from the top of the facebow. F to K, Whip 
Mix Quick Mount Facebow Technique. F, 
Armamentarium. G, Note that wax has 
been added to the mandibular incisor por- 
tion of the bitefork. Softening the wax. H, 
Adapting the bitefork to the maxillary 
teeth. 1, Thinning the posterior aspect of 
the wax further facilitates stabilization of 
the fork. J, Nasion relator being positioned. 
K, Knobs and toggles are tightened. 
(F, //to K, Courtesy Whip Mix Corporation. ) 



I 



SerCtion 1 Planning and Preparation 




A CR record slmuld 
ueivr be pcrforatt'd. 



^^^f 




Fig. 2-1 5. A CR record transfers the tooth relationships 
at CR from the patient to the articulator. 



positions can be reproduced from CR. A CR/MI 
slide will be readily reproducible on casts that have 
been articulated in CR. Thus, premature tooth con- 
tacts (deflective contacts) can be observed, and it 
can be determined whether an occlusal correction is 
necessary or appropriate before fixed prosthodontic 
treatment. Casts articulated in the maximum inter- 
cuspation (MI) position do not permit the evalua- 
tion of CR and retruded contact relationships. 
Therefore, the articulation of diagnostic casts in CR 
is of greater diagnostic value. 

When using a kinematic facebow, in theory, the 
thickness of a terminal hinge record is unimportant; 
a thicker record merely increases the amount of 
rotation. When using an arbitrary facebow, any arc- 
ing movement will result in some degree of inaccu- 
racy. Both techniques are subject to small errors, 
which can be minimized by keeping the record 
thin. However, it is essential that the teeth not 
perforate the record. Any tooth contact during 
record fabrication can cause mandibular translation 
due to neuromuscular protective reflexes governed 





Fig. 2-1 6. Incorrect CR recording. A, If the mandible is 
forced backward (F), the condyles will not be in their most 
superior position but will be moved backward and down- 
ward (arrow). B, Any restorations made on casts related 
with this CR record will be in supraclusion when tried in 
the mouth. C, Note the relationship of the anterior teeth. 



by mechanoreceptors in the periodontium, render- 
ing the resulting articulation useless. 

Jaw Manipulation. Accurately mounted casts 
depend on precise manipulation of the patient's 
mandible by the dentist. The condyles should re- 
main in the same place throughout the opening-clos- 
ing arc. Trying to force the mandible backward will 
lead to downward translation of the condyles, and 
restorations made to such a mandibular position 
will be in supraclusion at the try-in stage (Fig. 2-16). 

The load-bearing surfaces of the condylar pro- 
cesses, which face anteriorly, should be manipulated 
into apposition with the mandibular fossae of the tem- 
poral bones, with the disk properly interposed. The 
ease with which this can be accomplished depends on 
the degree of the patient's neuromuscular relaxation 



Chapter 2 Diagnostic Casts and Related Proced iires 



I 



^ 



^ ^ 




^V^ 



^^ ■■*■! 






Fig. 2-17. Manipulating a patient's mandible into cen- 
tric relation. Note the position of the examiner's thumbs 
and fingers on the mandibular border. The bimanual (A) 
and the single-handed technique (B). 



and on sound technique. The latter, in turn, depends 
on the patient permitting the dentist to control the 
mandible. Attempts to force or shake the mandible 
will lead to a protective muscle response by the patient. 
The bimanual manipulation technique described 
by Dawsonl2 is recommended as a reproducible tech- 
nique '3 that can be reliably learned . 14 In this tech- 
nique, the dental chair is reclined and the patient's 
head is cradled by the examiner. With both thumbs 
on the chin and the fingers resting firmly on the infe- 
rior border of the mandible (Fig. 2-17, A), the exam- 
iner exerts gentle downward pressure on the thumbs 
and upward pressure on the fingers, manipulating 
the condyle-disk assemblies into their fully seated 
positions in the mandibular fossae. Next, the 
mandible is carefully hinged along the arc of terminal 
hinge closure. Note: It is more difficult to ensure that 
the condyles will be properly located when the sin- 
gle-handed approach (Fig 2-17, B) is used with the 
fingers exerting upward pressure, although this tech- 
nique does allow the other hand to hold the record. 

Anterior Programming Device (Fig. 2-18). In 

some patients in whom CR does not coincide with IP, 




^4k 




Fig. 2-1 8. An anterior programming device is used to 
facilitate centric relation recording. A, Autopolymerizing 
resin is adapted to the maxillary central incisors. The pa- 
tient is guided into closure and stopped when the poste- 
rior teeth are about 1 mm apart. The indentations are 
used as a guide during trimming of the device (B). The 
completed device (C) should allow the patient to make 
smooth lateral and protrusive movements. An inclined 
contact area must be avoided, because it will tend to 
retrude the mandible excessively. D, Cross section 
through device. 



I 



Section 1 Planning and Preparation 



protective reflexes may be encountered. Because of 
well-established protective reflexes that are rein- 
forced every time the teeth come together, such pa- 
tients will not allow their mandible to be manipu- 
lated and hinged easily. If tooth contact can be 
prevented, they will "forget" these reflexes, and 
manipulation becomes easier. The teeth can be kept 
apart with cotton rolls, a plastic leaf gauge, or a small 
anterior programming device made of autopolymer- 
izing acrylic resin (also known as a Lucia jig). " 

If the mandible cannot be manipulated satisfacto- 
rily after an anterior programming device has been 
in place for 30 minutes, marked neuromuscular 
dysfunction is likely. Normally this is relieved by 
providing an occlusal device (whose fabrication and 
adjustment are described in Chapter 4). 

Centric Relation Recording Technique. Differ- 
ent techniques can be used to make a CR record. The 
choice of recording medium is to some degree a 
function of the casts to be articulated. For instance, 
very accurate casts made from elastomeric impres- 
sion materials can be articulated with a high- accu- 
racy interocclusal record material such as polyvinyl 
siloxane. On the other hand, less accurate diagnostic 
casts poured from irreversible hydrocolloid are bet- 
ter articulated using a more "forgiving" material 
such as interocclusal wax, provided that the record is 
properly reinforced. Most studies have shown con- 
siderable variability among various registration ma- 
terials and techniques, ^^ so particular care is needed 
with this procedure. 

Reinforced Aluwax Record. The reinforced 
Aluwax record is a "forgiving" method for record- 
ing the CR position. It is a reliable technique, origi- 
nally described by Wirth" and Wirth and Aplin,18 
and has provided consistent results. 1920 

Armamentarium (Fig. 2-19, A) 

• Heat-retaining wax sheet (i.e., Aluwax)* 

• Soft metal sheet (Ash's metal)* 

• Sticky wax 

• Scissors 

• Ice water 

Step-by-step Procedure 

1. Soften half a sheet of occlusal wax in warm wa- 
ter and adapt it to the maxillary cusp tips. Al- 
low the patient to close lightly and make cus 
pal indentations of the mandibular teeth (Fig. 
2-19, B). These indentations form no part of the 
record, but they thin the wax slightly and indi- 

*See Appendix A. 



cate the approximate positions of the man- 
dibular teeth for later reference. 

2. Add baseplate wax to the mandibular ante- 
rior region of the record and seal along the 
periphery (Fig. 2-19, C, D). 

3. Readapt the record to the maxillary teeth, re- 
softening if necessary. Guide the patient into 
centric closure, making shallow indentations 
in the baseplate wax. Verify that no posterior 
tooth contact occurs. If it does, add an addi- 
tional layer of baseplate wax (Fig. 2-19, E, F). 

4. Remove the record carefully and verify that 
no distortion has occurred. Then chill it thor- 
oughly in ice water. 

5. Reseat the record on the maxillary teeth and 
evaluate it for stability. If the maxillary cast is 
available, evaluate the fit on this as well. 

6. Add heat-retaining wax in the mandibular 
incisor region only (Fig. 2-19, G) and manip- 
ulate the mandible as previously described. 
Having the patient in a supine position for 
this manipulation allows better control. 

7. Make indentations of the mandibular incisor 
tips in the wax, repeating several times to en- 
sure reproducibility. Remove the wax record 
and rechill it in ice water until the anterior in- 
dentations are hard (Fig. 2-19, H, I). 

8. Add a small amount of heat-retaining wax in 
the mandibular posterior region and reseat 
the record (Fig. 2-19, J, K). Then guide the 
mandibular teeth into the anterior indenta- 
tions and have the patient close lightly. The 
baseplate wax will prevent excessive closure. 
Excessive force may distort the record or flex 
the mandible. The elevator muscles of the 
mandible will ensure that the most superior 
position of the condylar processes is recorded. 

9. Remove the record and chill it (Fig. 2-19, L). If 
there is difficulty in obtaining an undistorted 
record, the palatal area can be reinforced with 
the soft metal sheet (Fig. 2-19, D). Be sure that 
it is kept away from the indentations. Also re- 
member that when new wax is added, the 
record should be dried; otherwise, the wax 
will not adhere and may become detached. 

The advantage of this sequential technique is that 
the CR position is reproduced multiple times as the 
record is generated. The heat-retaining Aluwax is 
soft and distorts easily. Therefore, if the patient is not 
guided into exactly the same position, this problem 
will become readily apparent. Once the completed 
record has been obtained with adequate but fairly 
shallow indentations for all cusps, the same arcing 
motion has been reproduced four times, confirming 
that the CR position has been accurately captured. 



Chapter 2 Diagnostic Casts and Related Procedures 
B C 



I 







M 







D 






H 



C 




K 






Fig. 2-19. CR recording technique. The reproducibihty of the CR position is verified because CR has 
to be reproduced several times while the record is made. A, Armamentarium. B, A sheet of soft Aluwax 
is adapted to the maxillary arch. C, A piece of hard pink wax is added to the lower anterior portion of 
the wafer. D, Some Ash's Metal #7 is folded around the posterior border and luted to the wafer with 
sticky wax to increase rigidity. E, Note that the maxillary indentations capture only the cusp tips. F, The 
reinforced sheet is repositioned and the mandible is guided into CR until the pink wax provides a stop 
for vertical closure. G, Some Aluwax is added to the lower incisor indentations. H, The record is reposi- 
tioned and the CR closure repeated. I, The incisor indentations are reproduced in the Aluwax. J, After 
additional wax is added to the area of the first molars, hinge closure is repeated. The molar indentations 
are clearly visible. The incisor indentations should have been reproduced. Any "double" indentation in- 
dicates inaccuracy. K, The CR closure is repeated one more time after additional Aluwax is added to the 
premolar regions. L, The completed CR record. 

(Courtesy Dr. J. N. Nelson.) 



■ 



SerCtion i Plan ning and Preparation 



Anterior Programming Device with Elasto- 
meric or ZOE Record 
A rm am entarium 

• Self-curing resin 

• Petroleum jelly 

• Elastomeric material 

• Syringe 

• Scalpel blade 

Step-by-step Procedure 



1. 



2. 



3. 



4. 



Fabricate an anterior programming device 
from self-curing resin. The resin should be 
mixed to the consistency of putty and, after lu 
brication of the central incisors with petro- 
leum jelly, adapted to the teeth. The lingual as- 
pect of the anterior programming device 
should follow the lingual contours of the teeth. 
After trinmiing, it should result in separation 
of the posterior teeth (see Fig. 2-18, D). When 
the patient closes on the anterior program- 
ming device, no translation should occur. 
Verify that no posterior contact remains and 
that the only occlusal contact is on the ante- 
rior programming device. The device should 
be stable and remain in position. If necessary, 
some petroleum jelly can be applied to its in- 
ternal surface. 

Rehearse the closing of the mandible with the 
patient until a reproducible CR position is 
obtained. 

Verify that the syringe tip is large enough to 
permit free flow of the elastomeric material. 
Enlarge the opening of the syringe tip if nec- 
essary by trimming it with a scalpel blade. 



5. Dispense and mix the elastomeric material 
according to the manufacturer's instructions 
(Fig. 2-20, A). (The Automix materials are 
convenient.) 

6. Blow the occlusal surfaces of the teeth dry, 
and syringe the material onto the occlusal of 
the mandibular arch (Fig. 2-20, B). 

7. Guide the patient's mandible into hinge move- 
ment until the mandible comes to rest on the 
anterior programming device. Maintain this 
position until the material has set (Fig. 2-20, C). 

8. Remove the record from the mouth and trim 
with the scalpel blade following the buccal 
cusps (Fig. 2-20, D). 

9. Verify that the mandibular and maxillary 
casts seat fully in the record. 

As an alternative to the use of elastomeric mater- 
ial, a gauze mesh with zinc oxide-eugenol occlusal 
registration paste can be used (Fig. 2-27). The step- 
by-step procedure follows the one described for the 
elastomeric technique. However, rather than syring- 
ing the material onto the mandibular arch, the prac- 
titioner should coat the interocclusal cloth forms 
outside the mouth and interpose them, after which 
the patient can be guided into CR. Care must be 
taken, however, to position the frame that holds the 
cloth form so it does not interfere with the closure 
movement. 

Other alternatives include using impression plaster 
or autopolymerizing resin as the recording medium. 
In all these techniques, accuracy depends on complete 
seating of the casts into the recording medium. Seating 
is often prevented by better detail reproduction in the 
record than in the casts, especially around the fossa. 




Fig. 2-20. ^ Elastomeric material for CR recording. B, Mandibular quadrants coated. C, The patient 
remains occluded until the material has set. D, The completed record must be evaluated after trimming. 

(^ Courtesy Sullivan-Sehein Dental.) 



Chapter 2 Diagnostic Casts and Related Procedures 



I 



This additional detail needs to be carefully trimmed 
until the cast is completely seated in the record. 

Recording Jaw Relationships in Partially Eden- 
tulous Dentitions (Fig. 2-22). When there are insuf- 
ficient teeth to provide bilateral stability, obtaining a 
CR record as described may not be possible. As a re- 
sult, acryhc resin record bases must be fabricated. To 



avoid errors caused by soft tissue displacement, 
which prevents accurate transfer of rigid materials 
from one set of casts to another, these bases should be 
made on the casts that are to be articulated. If break- 
age of the casts is a concern, it may be advisable to 
make record bases on an accurate duplicate cast 
made with reversible agar hydrocolloid impression 
material in a flask designed for that purpose. 




Fig. 2-21 . Gauze mesh cloth forms with plastic holders, and ZOE paste can be used instead of elas- 
tomeric paste. 




Fig. 2-22. Acrylic resin record base for mounting 
a partially edentulous cast. 



I 



Section 1 Planning and Preparation 



Articulating the Diagnostic Casts 

Maxillary Cast (Fig. 2-23). The maxillary cast is 
seated in the indentations on the facebow fork after 
the facebow is attached to the articulator. Wedges or 
specially designed braces can be used to support the 
weight of the cast and to prevent the fork from flex- 
ing or moving. After it has been scored and wetted, 
the cast is attached to the mounting ring of the ar- 
ticulator with a low-expansion, fast-setting mount- 
ing stone or plaster. 

Mandibular Cast (Fig. 2-24). To relate the 
mandibular cast properly to the maxillary cast, the 
incisal guide pin should be lowered sufficiently to 
compensate for the thickness of the centric relation 
record. The articulator is inverted, and the record is 
seated on the maxillary cast. The mandibular cast is 
then carefully seated in the record, and each cast is 
checked for stability. The maxillary and mandibular 
casts can be luted together with metal rods, or 
pieces of wooden tongue blade, and sticky wax. The 
mandibular member of the articulator is closed into 
mounting stone; the condylar balls should be fully 
seated in the corresponding fossae. If the articulator 
has a centric latch, this step is simphfied. Otherwise, 
the articulator should be held until the stone has 
reached its initial set. No attempt should be made to 
smooth the stone until it has fully set. 

Evaluation (Fig. 2-25) 

Accuracy is critical in both centric relation and the 
intercuspal position. Before the articulator controls 
are adjusted, the accuracy of CR must be confirmed 
by comparing the tooth contacts on the casts with 
those in the mouth. During the clinical examination, 
the position of tooth contacts in CR can be marked 
with thin articulating film. Normally, the markings 
will be on the mesial inclines of maxillary cusps and 
the distal inclines of mandibular cusps. Their exact 
location can be transferred by having the patient 
close through thin occlusal indicator wax. The artic- 
ulated casts are closed and the retruded tooth con- 
tacts marked with articulating film. When the indi- 
cator wax is transferred to the casts, the perforations 
should correspond exactly to these marks. 

For additional verification, the intercuspal posi- 
tion of the articulated casts should be examined. 
Maximum intercuspation is usually a translated 
mandibular position that may not be reproducible 
with absolute accuracy on a semiadjustable articula- 
tor. However, any substantive discrepancy invariably 
indicates an incorrect mounting. If further confirma- 
tion of mounting accuracy is required (as may be the 
case when working casts are being articulated), addi- 
tional CR records can be made and compared with a 
split cast mounting system or a measuring device 
such as the Denar Vericheck (Fig. 2-26). 



Posterior Articulator Controls 

The advantages and disadvantages of the different 
articulators are summarized in Table 2- 1 . The more 
sophisticated (fully adjustable) articulators have a 
large range of adjustments that can be programmed 
to follow the condylar paths precisely. Their posterior 
controls are designed to permit simulation of move- 
ment of the condylar processes, duplicating protru- 
sive and lateral tooth contacts. The semiadjustable in- 
struments can be adjusted to a lesser extent. Their 
posterior controls are designed to replicate the most 
clinically significant features of mandibular move- 
ment (e.g., condylar inchnation and mandibular side 
shift). These instruments can be programmed from 
eccentric interocclusal records or a simplified panto- 
graph. An alternative technique is to use average val- 
ues for the control settings. It is important to note that 
no method used to program an articulator to repro- 
duce eccentric jaw movements is without error ^^ 

Arbitrary Values. Based on clinical investiga- 
tions, certain generally applicable average anatomic 
values have evolved for condylar inclination, im- 
mediate and progressive sideshift. These values 
have been described relative to the Frankfort hori- 
zontal plane and the midsagittal plane. For instance, 
an average value of 1.0 mm has been reported 23 for 
immediate sideshift. 

When arbitrary values are used to adjust posterior 
articulator controls, the actual instrument settings 
will vary from one manufacturer to another. How- 
ever, depending on the degree of adjustabihty of the 
articulator, using arbitrary values is not necessarily 
less accurate than alternative techniques (e.g., eccen- 
tric interocclusal records to program a semiad- 
justable articulator, particularly when the instru- 
ment can execute only a straight protrusive path). 

Eccentric Interocclusal Recordings. Eccentric in- 
terocclusal records (check-bites) have been recom- 
mended" for setting the posterior controls of a 
semiadjustable articulator. These consist of wax or 
another recording material interposed between the 
maxillary and mandibular arches; they record the 
position of the condyles in eccentric mandibular po- 
sitions. Static positional records are made in trans- 
lated jaw positions: a protrusive record and two lat- 
eral records. The protrusive record can be used to 
adjust both condylar inclinations on the articulator, 
and the lateral records are used to adjust the side 
shift on semiadjustable articulators. 

An articulator set by an eccentric record is accu- 
rate in only two positions: at CR and at the position 
recorded by the record (Fig. 2-27). This occurs be- 
cause the path taken between these may differ sig- 
nificantly on the articulator from what is actually 
performed by the mandible. A semiadjustable 
instrument may have a protrusive and a sideshift 



rh^pter 9, Dingnostic Cnsts and Related Procedures 
B C 



I 





H 





Fig. 2-23. Mounting the maxillary cast on a Whip Mix articulator. 
A, Remove the incisal pin. B, Adjust the condylar inclination to the facebow 
setting. C, Set the sideshift to zero. D, Attach a mounting plate. E, Attach the 
facebow earpieces to the condylar elements. F, Facebow attached to the artic- 
ulator. G, Position the scored maxillary cast on the bitefork and prewet the 
cast. H, Mounting stone is applied to the cast and the mounting plate. 
I, Close the upper member of the articulator until it contacts the cross bar of 
the facebow. J, Add additional stone as needed. 

(Courtesy Whip Mix Corporation.) 



I 



Section i Planning and Preparation 




Fig. 2-24. Mounting the mandibular cast. A to D, Denar articulator. A, Position the CR record on the 
inverted maxillary cast. B, Adjust the incisal guide pin and orient the mandibular cast in the record. 
C, Attach the cast with mounting stone. D, When the pin is raised, the casts will contact in CR closure. 
E to H: Whip Mix articulator. E, Position the CR record. F, The incisal guidepin is adjusted, the cast is 
stabihzed, and plaster is applied to the prewetted cast and the mandibular mounting plate. G, Close the 
articulator. H, Completed mounting. 
(E to H Courtesy Whip Mix Corporation.) 



Chapter 2 Diagnostic Casts and Related Procedures 



I 





Fig. 2-25. Verifying mounting accuracy. A, Occlusal in- 
dicator wax is adapted to the maxillary teeth, and the pa- 
tient is guided into CR closure. B, The cast contacts are 
marked with thin articulating film. C, If the mounting is 
accurate, the markings will correspond to perforations in 
the wax. 



Fig. 2-26. The Denar Vericheck. The casts are positioned 
in the same relationship as on the articulator, but the 
condylar elements are replaced by four styli. Each marks 
graph paper attached to the maxillary half of the articula- 
tor. Successive CR records can be compared by examining 
these marks. 
(Courtesy Denar Corporation.) 



More -^- 
More -*- 
More -♦- 

Less 



Mulfiple opposing 
restorations 

No anterior 
gu id once 

Extensive occlusal 
pathology 



WW«I1^L^'BI'1%.1 


Fja#*i.^L'4%i«i« 








Futly Adjustable 


Semicidjustable 


iMonadjustable 


Unmounted C^ists 






Denar D5-A 
Stuart 

TMJ 




Arcon Nona re on 
Denar Mark 11 Hanau 96H20 

Whip Mix Dent^tus 
Hanau 183-2 


Large Small 


Arch Quadrant 



Diagnostic information provided 



- Occlusal information conveyed to laboratory 
-Time and skill needed at initial appointment ^ 
-^ Chair time needed before cementation — 



Dfagnostic assessment and treat- 
ment of most patients requiring 
fixed prosthodontics 



Larger articulators for 
single restorations; 
some adjustment 
necessary 

Small hinge articulator 
only when occlusal 
influence minimal 



Less 

Less 

Less 

1^ More 

Only v/hen occlusal influ- 
ence minimal 



Modified sJigiitly irom i^osenstiel SF: In Rayne J. editor: Cetit'ml dental treafment, London, 1983, KJuwer Publishing, 



I 



Section 1 Planning and Preparation 




[t-line a rti evil a to rs ^i re 
accurate only mCR and the 
posilion where the excursive 
records are made. 




fig. 2-27. A, The typical condylar path is curved, with its steepest inchnation near CR. If a semiad- 
justable articulator with a straight condylar path is programmed from an eccentric record, very different 
values will be obtained (depending on where the record is made) from what is actually performed by 
the mandible. B, Record made at Position 1. C, Record made at Position 2. 



path that are straight lines, whereas the true paths 
will invariably be curved. In an attempt to minimize 
errors, many contemporary semiadjustable articula- 
tors come with curved fossae. 

A rm am entarium 

• Interocclusal wax record material 

Step -by -step Technique 

1. Practice the three excursive positions with 
the patient until they can be reproduced. 
The patient can be guided into an anterior 
end-to-end position and left and right lateral 
positions where the canines are end-to-end 
when viewed from the front. We have found 
guiding the patient helpful in obtaining the 
records easily, although unguided records 
have been equally accurate 25 

2. Adapt a wax record to the maxillary arch 
(Fig. 2-28, A) and guide the patient into a pro- 
trusive position. Have the patient close to 
form indentations in the recording medium 
(Fig. 2-28, B). Verify that the midline remains 
properly aligned and that when viewed from 
the side, the maxillary and mandibular in- 
cisors are end to end. 



3. For the lateral records, add additional wax to 
one posterior quadrant of a wax record to 
compensate for the additional space on the 
patient's nonworking side. 

4. Adapt this to the patient's maxillary arch and 
guide the patient's mandible into an excur- 
sive position, again verifying that the canines 
are end to end (Fig. 2-28, C, D). 

5. Repeat this step for the other lateral excursion. 

6. Mark each record to facilitate its identifica- 
tion when using it to adjust the posterior ar- 
ticulator controls (Fig. 2-28, E). 

Simplified Pantographs (Fig. 2-29). A simplified 
pantograph measures only certain components of 
mandibular movement thought to be of greatest 
clinical significance, usually the condylar inclina- 
tions and mandibular sideshift. This device can be 
quickly assembled. Numerical values are measured 
directly from the recording and are used to set a 
semiadjustable articulator to provide useful diag- 
nostic information. 

Simplified pantographs may reveal an exces- 
sively shallow condylar inclination or an exagger- 
ated mandibular sideshift. If either of these condi- 
tions are identified, restoration of the posterior teeth 
is likely to be complex, and the use of a fully ad- 
justable articulator is recommended. Some manu- 



Chapter 2 Diagnostic Casts and Related Procedures 



I 




Fig. 2-28. Eccentric interocclusal records. A, Adaptation of wax to the maxillary arch. B, Protrusive 
record. C and D, The patient is guided into left and right lateral excursive movements. Records are 
made in the left and right canine edge-to-edge positions. E, The completed records. 





Fig. 2-29. A, The Panadent Axi-Path Recorder. B, An axis stylus traces the condylar-path and measures 
the amount of Bennett movement while the patient is guided into an eccentric border movement (C). 
(A to C courtesy Panadent Corporation.) 



facturers offer inserts of standard "fossae" of vary- 
ing configuration, whose selection depends on the 
measurements obtained with a simplified panto- 
graph (Fig. 2-30). 

Pantographic Recordings (Fig. 2-31). Fully ad- 
justable articulators are usually programmed on the 
basis of a pantographic recording. Jaw movements 
are registered by directional tracings on recording 
plates. The plates are rigidly attached to one jaw, and 
the recording styli are attached to the other. A total of 
six plates are needed to achieve a precise movement 
record of the mandible. Left and right lateral border 
and protrusive tracings are made on each plate. The 
pantograph is then attached to the articulator, and 



the controls are adjusted and modified until the in- 
strument can faithfully reproduce the movements of 
the styh on the tracings (Fig. 2-32). A simpler, though 
less accurate, procedure is to measure the tracings 
directly and adjust the condylar controls without 
transferring the recordings. 

Electronic Pantograph (Fig. 2-33). The Axio- 

graph* is an electronic pantograph designed to 
record and measure functional and border move- 
ments. It consists of upper and lower bows that 
record and measure mandibular movements. 



*Great Lakes Orthodontics: Tonawanda, N.Y. 



I 



S faction i Planning and Preparation 




P«naid«nl 
pr«form«d motion analog patht 




Fig. 2-30. A, The Panadent PCH Ar- 
ticulator with support Legs. B, Fossa 
blocks (motion analogs) with different 
amounts of Bennett movement are se- 
lected from the simplified recorder or 
lateral check bites. The blocks are ro- 
tated to the correct condylar inclination. 
C, Schematic showing the sagittal and 
transverse planes of the available mo- 
tion analogs blocks. 
(A to C courtesy Panadent Corporation.) 




Fig. 2-31 . Pantographic recording with the Stuart instrument. 
(Courtesy Drs. R. Giering and J. Petrie.) 




Fig. 2-32. Pantographic tracings represent information that could only be obtained with an infinite 
number of excursive records: This simplified schematic shows the relative orientation of six recording 
plates (attached to the maxillary bow, omitted for clarity) to the scribing styli, attached to the mandibu- 
lar bow. W, Working movement; N, nonworking or balancing movement; P, protrusive movement. The 
CR position is represented by the intersection of the paths marked by the dot. 




Fig. 2-33. Electronic jaw recording system. The Axiotron is an electronic recording system that at- 
taches to the Axiograph pantograph. 

(Courtesy Great Lakes Orthodontics.) 



I 



Section 1 Planning and Preparation 




Fig. 2-34. A, B, The TMJ articulator is programmed from three-dimensional acrylic resin recordings. 
(Courtesy Dr. A. Peregrina.) 




Fig. 2-35. Mechanical anterior guide table. A, The pro- 
trusive path has been adjusted. The side screw adjusts the 
lateral flange. B, Lateral flange adjusted to the right work- 
ing movement. 



Stereograms (Fig. 2-34). Another approach to re- 
producing posterior condylar controls is to cut or 
mold a three-dimensional recording of the jaw 
movements. This "stereogram" is then used to form 
custom-shaped fossae for the condylar heads. 

A nterior Guidance 
Border movements of the mandible are governed by 
tooth contacts and by the shape of the left and right 
temporomandibular joints. In patients with normal 
jaw relationships, the vertical and horizontal over- 
lap of anterior teeth and the lingual concavities of 
the maxillary incisors are highly significant during 
protrusive movements. In lateral excursions, the 
tooth contacts normally existing between the ca- 
nines are usually dominant, although the posterior 
teeth may also be involved (see Chapter 4). Restora- 
tive procedures that change the shape of the ante- 
rior teeth can have a profound effect on excursive 
tooth contacts. For this reason, when preparation of 
anterior teeth is contemplated, the exact nature of 
the anterior contacts should be transferred to the ar- 
ticulator, where it can be studied and stored before 
these teeth are prepared. 

Mechanical A nterior Guidance Table (Fig. 2-35). 
Most articulator manufacturers supply a mechanical 
anterior guidance (incisal guidance) table. Such tables 
can be pivoted anteriorly and posteriorly to simulate 
protrusive guidance, and they have lateral wings that 
can be adjusted to approximate lateral guidance. 
However, the sensitivity of these adjustments is in- 
sufficient for successfully transferring the existing lin- 
gual contours of natural teeth to newly fabricated 
restorations. Therefore, the principal use for these me- 
chanical tables is in the fabrication of complete den- 
tures and occlusal devices (see Chapter 4). 



Chapter 2 Diagnostic Casts and Related Procedures 



■ 



Custom Acrylic Anterior Guidance Table. This 
simple device is used for accurately transferring to 
an articulator the contacts of anterior teeth when de- 
termining their influence on border movements of 
the mandible. Acrylic resin is used to record and 
preserve this information, even after the natural lin- 
gual contours of the teeth have been altered during 
preparation for complete coverage restorations. The 
technique is similar to that for stereographic record- 
ing used in setting the posterior controls of some 
articulators. 

Custom Guide Table Fabrication 
Armamentarium (Fig. 2-36, A) 

• Plastic incisal table 

• Tray and fossa acrylic resin 

• Petrolatum 

Step -by -step Procedure 

1. After raising and lubricating the pin, moisten 
the plastic incisal table with acrylic resin 
monomer to ensure a good bond (Fig. 2-36, 
B to D). 

2. Mix a small quantity of resin and mold it to 
the table (Fig. 2-36, E, F). 

3. Raise the incisal pin about 2 mm from the 
table, cover its tip with petrolatum, and close 
it into the soft resin (Fig. 2-36, G). 

4. Manipulate the articulator in hinge, lateral, 
and protrusive movements while the resin is 
in the doughy stage of polymerization (Fig. 
2-36, H to J). As the pin moves through these 
excursions, its tip will push into and mold 
the doughy acrylic resin lying in its path, ul- 
timately creating an accurate and rigid 
three-dimensional record of the mandibular 
movements and their lateral and protrusive 
limits through the functional range (Fig. 
2-36, K). 

5. Continue these closures until the resin is no 
longer plastic, being careful not to abrade or 
damage the casts during the process. A thin 
film of plastic foil placed between the casts 
will help minimize abrasion without signifi- 
cantly affecting the accuracy of the guide table. 

Evaluation 

When the custom anterior guidance table has 
been completed, the incisal pin should contact the 
table in all excursive movements. This can be 
checked with thin Mylar strips (shim stock). If con- 
tact is deficient, a small mix of new resin is added 
and the process repeated. If too much resin has been 
used, the table may interfere with the hinge open- 
ing-closing arc of the articulator (Fig. 2-37). Excess 
can be easily trimmed away. 



Diagnostic Cast Modification 

One advantage of having accurately articulated 
diagnostic casts is that proposed treatment proce- 
dures can be rehearsed on the stone cast before 
making any irreversible changes in the patient's 
mouth. These diagnostic procedures are essential 
when attempting to solve complicated problems. 
Even the most experienced clinician may have diffi- 
culty deciding between different treatment plans. 
Even in apparently simple situations, time that the 
practitioner spends rehearsing diagnostic proce- 
dures on the casts is usually well rewarded. 

Diagnostic cast modifications include the fol- 
lowing: 

1. Changing the arch relationship preparatory 
to orthognathic procedures when surgical 
correction of skeletal jaw discrepancy is to be 
performed 

2. Changing the tooth position before orthodon- 
tic procedures (Fig. 2-38) 

3. Modifying the occlusal scheme before at- 
tempting any selective occlusal adjustment 

4. Trial tooth preparation and waxing (Fig. 2-39) 
before fixed restorative procedures. (This is 
one of the most useful diagnostic techniques 
for patients seeking fixed prosthodontics. It 
enables the practitioner to rehearse a proposed 
restorative plan and to test it on a stone cast, 
providing considerable information in ad- 
vance of the actual treatment and helping to 
explain the intended procedure to the patient.) 

On many occasions it will be necessary to com- 
bine two or more of these options. In fact, most 
treatment planning decisions (e.g., preparation de- 
sign, choice of abutment teeth, selection of an opti- 
mum path of withdrawal of a fixed partial denture, 
or deciding to treat a patient with an FPD or an 
RPD) can be simplified by adhering to these diag- 
nostic techniques. 

SUMMARY 

Diagnostic casts provide valuable preliminary in- 
formation and a comprehensive overview of the pa- 
tient's needs often not apparent during the clinical 
examination. They are obtained from accurate irre- 
versible hydrocolloid impressions and should be 
transferred to a semiadjustable articulator using a 
facebow transfer and interocclusal record. For most 
routine fixed prosthodontic diagnostic purposes, 
the use of an arbitrary hinge axis facebow is suffi- 
cient. If special concerns apply, such as a change in 
vertical dimension, a kinematic facebow transfer is 
needed. Two types of articulators are recognized: 
arcon and nonarcon. For highly complex treatment 



I 



S faction 1 Planning and Preparation 

A B 





H 




K 




Fig. 2-36. Fabrication of a custom 
anterior guidance table. A, Arma- 
mentarium. B, Incisal pin is raised 1 
or 2 mm. C, Lubricate the tip of the 
pin. D, Wet the table with monomer. 

E, Dispense and mix resin of choice. 

F, Apply resin to acrylic table. G, In- 
sert pin into doughy resin. H, Track 
the protrusive path. 1, Right working 
movement and all intermediate lat- 
erotrusive paths. J, Left working 
movement and all intermediate lat- 
ertmsive paths. K, Allow resin to set; 
excess resin still needs to be re- 
moved. 

(Courtesy Whip Mix Corporation.) 



Chapter 2 Diagnostic Casts and Related Procedures 



I 




Fig. 2-37. A, A custom anterior guidance table made with excess resin. This must be trimmed if it in- 
terferes with the path of closure of the incisal pin. B, The completed table with excess resin ground 
away. Note the lateral and protrusive paths. 




Fig. 2-38. Diagnostic cast modifications in advance of orthodontic treatment. 



needs, a fully adjustable articulator may be indi- 
cated. Such articulators are adjusted by using a pan- 
tographic tracing. 

Diagnostic casts should be articulated in centric 
relation to enable observation of deflective tooth 
contact and to assess any slide that may be present 
from CR to IP Centric relation is defined as the max- 
illomandibular relationship in which the condyles 
articulate with the thinnest avascular portion of 
their respective disks with the complex in the 
anterior-superior position against the shapes of the 
articular eminences. This position is independent of 
tooth contact. It is recorded with a suitable medium 
interposed between the maxillary and mandibular 
teeth and by guiding the patient into the CR posi- 
tion. This can be accomphshed through bimanual 
manipulation. If many teeth are absent, record bases 



with wax rims may need to be fabricated to obtain a 
centric relation record. 

If a patient's mandible is difficult to manipulate 
into a reproducible hinge movement, a deprogram- 
ming device is helpful. These can be used to help 
minimize "muscle memory," resulting in easier 
rephcation of the rotational hinge movement of the 
mandible. 

Posterior articulator controls can be adjusted on 
the basis of arbitrary values based on anatomic av- 
erages, by means of eccentric records, simplified 
pantographs, pantographs, or stereographs. 

Anterior guidance can be approximated on artic- 
ulators with a mechanical guide table. As an alter- 
native, a custom acrylic guide table can be gener- 
ated from the diagnostic casts. The latter is useful 
when anterior teeth are to be restored. 



I 



Section i Planning and Preparation 

A B 





H 





Fig. 2-39. Diagnostic waxing procedure. Diagnostic tooth preparation and waxing help simplify com- 
plex prosthodontic treatment planning for predictable results. A, Before treatment. The patient needs ex- 
tensive fixed and removable treatment. B and C, Cross-mounted diagnostic casts. A record base is used 
to articulate the partially edentulous mandibular cast. D and E, Diagnostic tooth preparations determine 
the correct reduction for esthetics and function. F to I, Diagnostic waxing, done in conjunction with di- 
agnostic denture tooth arrangement. 
(Courtesy Dr. J. Bailey.) 



If Quexiiom 



1. Discuss the uses and limitations of irreversible hydrocolfoid and include an overview of ifs material 
properties. 

2. Why are diagnostic casts orficulaled m centric relation? Why aren't they articubted in the intercuspal 
position? 

3. List five items that are easier to determine on diagnostic casts rather than intraorally. 

4. What (s accomplished with a facebow transfer? How do arbitrary facebows differ from kinematic face- 
bows? When would one be selected over the other? 

5. Describe the differences between arcon and nonarcon articulators. When would use of a simple hinge 
instrument be acceptable and when would it be contra indicated? Why? 

6. What is the role of excursive records in adjusting the articulator? 

7. What does o simplified pantograph record? What does a pantograph record? When would either be 
indicated? 

8. For what purpose is a custom acrylic guide table fabricated, and when ?s its use necessary? 

9. Give two examples when a diagnostic waxing procedure is indicated. 



Chapter 2 Diagnostic Casts and Related Procedures 



I 



Diagnostic procedures such as diagnostic wax- 
ing, tooth preparation, and diagnostic cast modifi- 
cation can greatly enhance diagnosis and treatment 
planning. 



OWSSAIiQ 




adjustable anterior guidance: an anterior guide on an 
articulator whose surface may be altered to provide 
desired guidance of the articulator's movement 
mechanism: the guide may be programmed (cali- 
brated) to accept eccentric interocclusal records. 

agar: n (1889) a complex sulfated polymer of galac- 
tose units, extracted from Gelidium canilagineum, 
Gracilaria confervoides, and related red algae. It is 
a mucilaginous substance that melts at approxi- 
mately 100°C and solidifies into a gel at approxi- 
mately 40°C. It is not digested by most bacteria and 
is used as a gel in dental impression materials and 
solid culture media for microorganisms. 

anterior guidance: 1: the influence of the contacting sur- 
faces of anterior teeth on tooth-limiting mandibular 
movements. 2: the influence of the contacting sur- 
faces of the guide pin and anterior guide table on ar- 
ticular movements. 3: the fabrication of a relationship 
of the anterior teeth preventing posterior tooth con- 
tact in all eccentric mandibular movements. 

anterior guide pin: that component of an articulator, 
generally a rigid rod attached to one member, con- 
tacting the anterior guide table on the opposing 
member. It is used to maintain the established verti- 
cal separation. The anterior guide pin and table, to- 
gether with the condylar elements, direct the move- 
ments of the articulator's separate members. 

anterior guide table: that component of an articulator 
on which the anterior guide pin rests to maintain 
the occlusal vertical dimension and influence artic- 
ulator movements. The guide table influences the 
degree of separation of the casts in all relationships. 

anterior programming device: an individually fabri- 
cated anterior guide table that allows mandibular 
motion without the influence of tooth contacts and 
facilitates the recording of maxillomandibular rela- 
tionships; also used for deprogramming. 

anterior reference point: any point located on the 
midface that, together with two posterior reference 
points, estabhshes a reference plane. 

arbitrary face-bow: a device used to arbitrarily relate 
the maxillary cast to the condylar elements of an ar- 
ticulator. The position of the transverse horizontal 
axis is estimated on the face before using this device. 

arcon: n a contraction of the words articulator and 
condyle, used to describe an articulator containing 
the condylar path elements within its upper mem- 



ber and the condylar elements within the lower 
member. 

arcon articulator: an articulator that applies the arcon 
design. This instrument maintains anatomic guide- 
Hnes by the use of condylar analogs in the mandibu- 
lar element and fossae assemblies within the maxil- 
lary element. 

arrow point tracer: 1: a mechanical device used to 
trace a pattern of mandibular movement in a se- 
lected plane-usually parallel to the occlusal plane. 
2: a mechanical device with a marking point at- 
tached to one jaw and a graph plate or tracing plane 
attached to the other jaw. It is used to record the di- 
rection and range of movements of the mandible. 

articulator: n a mechanical instrument that represents 
the temporomandibular joints and jaws, to which 
maxillary and mandibular casts may be attached to 
simulate some or all mandibular movements- 
usage: articulators are divisible into four classes. 
Class I articulator: a simple holding instrument ca- 
pable of accepting a single static registration. Verti- 
cal motion is possible. Class II articulator: an instru- 
ment that permits horizontal as well as vertical 
motion but does not orient the motion to the tem- 
poromandibular joints. Class III articulator: an in- 
strument that simulates condylar pathways by us- 
ing averages or mechanical equivalents for all or 
part of the motion. These instruments allow orien- 
tation of the casts relative to the joints and may be 
arcon or nonarcon instruments. Class IV articulator: 
an instrument that will accept three-dimensional 
dynamic registrations. These instruments allow ori- 
entation of the casts to the temporomandibular 
joints and repHcation of all mandibular movements. 

average axis face-bow: a face-bow that relates the 
maxillary teeth to the average location of the trans- 
verse horizontal axis. 

average value articulator: an articulator that is fabri- 
cated to permit motion based on mean mandibular 
movements-also called Class III articulator. 

centric relation: 1: The maxillomandibular relationship 
in which the condyles articulate with the thinnest 
avascular portion of their respective disks with the 
complex in the anterior- superior position against 
the shapes of the articuaar eminences. This position 
is independent of tooth contact. This position is 
clinically discernible when the mandible is directed 
superior and anteriorly. It is restricted to a purely 
rotational movement about the transverse horizon- 
tal axis (OPT 5) 2: The most retruded physiologic re- 
lation of the mandible to the maxillae to and from 
which the individual can make lateral movements. 
It is a condition that can exist at various degrees of 
j aw separation. It occurs around the terminal hinge 
axis (GPT-3) 3: The most retruded relation of the 
mandible to the maxillae when the condyles are in 



■ 



Section 1 Planning and Prep aration 



the most posterior unstrained position in the glenoid 
fossae from which lateral movement can be made, at 
any given degree of jaw separation (GPT-1) 4: The 
most posterior relation of the lower to the upper jaw 
from which lateral movements can be made at a 
given vertical dimension (Boucher) 5: A maxilla to 
mandible relationship in which the condyles and 
disks are thought to be in the midmost uppermost 
position. The position has been difficult to define 
anatomically but is determined clinically by assess- 
ing when the jaw can hinge on a fixed terminal axis 
(up to 25 mm). It is a clinically determined relation- 
ship of the mandible to the maxilla when the condyle 
disk assemblies are positioned in their most superior 
position in the mandibular fossae and against the 
distal slope of the articular eminence (Ash) 6: The re- 
lation of the mandible to the maxillae when the 
condyles are in the uppermost and rearmost position 
in the glenoid fossae. This position may not be able 
to be recorded in the presence of dysfunction of the 
masticatory system 7: A clinically determined posi- 
tion of the mandible placing both condyles into their 
anterior uppermost position. This can be determined 
in patients without pain or derangement in the TMJ 
(Ramsfjord) Boucher CO. Occlusion in prosthodon- 
tics. J Prosthet Dent 1953; 3:633-56. Ash MM. Per- 
sonal communication, July 1993. Lang BR, Kelsey 
CC. International prosthodontic workshop on com- 
plete denture occlusion. Ann Arbor: The University 
of Michigan School of Dentistry; 1973. Ramsfjord SP. 
Personal communication, July 1993. 

centric relation record: a registration of the relation- 
ship of the maxilla to the mandible when the 
mandible is in centric relation. The registration may 
be obtained either intraorally or extraorally, 

condylar hinge position: obs the position of the con- 
dyles of the mandible in the glenoid fossae at which 
hinge axis movement is possible (GPT-4). 

deprogrammer: n various types of devices or materi- 
als used to alter the proprioceptive mechanism dur- 
ing mandibular closure. 

diagnostic cast: a life-size reproduction of a part or 
parts of the oral cavity and/or facial structures for 
the purpose of study and treatment planning. 

face-bow: a caliper-like instrument used to record the 
spatial relationship of the maxillary arch to some 
anatomic reference point or points, which then 
transfers this relationship to an articulator; it orients 
the dental cast in the same relationship to the open- 
ing axis of the articulator. Customarily, the ana- 
tomic references are the mandibular condyle's 
transverse horizontal axis and one other selected 
anterior point; also called hingebow. 

face-bow fork: that component of the face-bow used 
to attach the occlusion rim to the face-bow. 

face-bow record: the registration obtained by means 
of a face-bow. 



Frankfort horizontal plane: 1: eponym for a plane estab- 
lished by the lowest point in the margin of the right 
or left bony orbit and the highest point in the margin 
of the right or left bony auditory meatus. 
2: a horizontal plane represented in profile by a line 
between the lowest point on the margin of the orbit to 
the highest point on the margin of the auditory mea- 
tus; adopted at the 13th General Congress of German 
Anthropologists (the Frankfurt Agreement) at Frank- 
furt am Main, 1882, and finally by the International 
Agreement for the Unification of Craniometric and 
Cephalometric Measurements in Monaco in 1906; 
also called auriculo-orbital plane, eye-ear plane, 
Frankfurt horizontal (FH), Frankfurt horizontal line. 

fully adjustable articulator: an articulator that allows 
replication of three-dimensional movement of re- 
corded mandibular motion-also called Class IV 
articulator. 

fully adjustable gnathologic articulator: an articulator 
that allows replication of three dimensional move- 
ment plus timing of recorded mandibular motion- 
also called Class IV articulator. 

horizontal plane of reference: a horizontal plane estab- 
lished on the face of the patient by one anterior ref- 
erence point and two posterior reference points 
from which measurements of the posterior ana- 
tomic determinants of occlusion and mandibular 
motion are made. 

hydrocolloid: n (1916) a colloid system in which water 
is the dispersion medium; those materials described 
as colloid sols with water that are used in dentistry 
as elastic impression materials. 

incisal guidance: 1: the influence of the contacting sur- 
faces of the mandibular and maxillary anterior teeth 
on mandibular movements 2: the influence of the 
contacting surfaces of the guide pin and guide table 
on articulator movements. 

I nterocclusal record : a registration of the positional re- 
lationship of the opposing teeth or arches; a record 
of the positional relationship of the teeth or jaws to 
each other. 

irreversible hydrocolloid: a hydrocolloid consisting of 
a sol of alginic acid having a physical state that is 
changed by an irreversible chemical reaction form- 
ing insoluble calcium alginate-called also alginate, 
dental alginate. 

kinematic face-bow: a face-bow with adjustable 
caliper ends used to locate the transverse horizontal 
axis of the mandible. 

lateral interocclusal record: a registration of the posi- 
tional relationship of opposing teeth or arches made 
in either a right or left lateral position of the mandible. 

leaf gauge: a set of blades or leaves of increasing 
thickness used to measure the distance between 
two points or to provide metered separation. 

Lucia jig: [Victor O. Lucia, U.S. prosthodontist]: 
eponym-see anterior programming device (Lucia 



Chapter 2 Diagnostic Casts and Related Procedures 



I 



VO. Treatment of the edentulous patient. Chicago: 

Quintessence, 1986.) 

maxillomandibular relationship record: a registration 
of any positional relationship of the mandible rela- 
tive to the maxillae. These records may be made at 
any vertical, horizontal, or lateral orientation. 

mounting: v the laboratory procedure of attaching a 
cast to an articulator or cast relator. 

mounting plate: removable metal or resin devices that 
attach to the superior and inferior members of an 
articulator, which are used to attach casts to the 
articulator. 

nonadjustable articulator: an articulator that does 
not allow adjustment to replicate mandibular 
movements. 

occlude: b occluded; occluding: vt (1597) 1: to bring to- 
gether; to shut 2: to bring or close the mandibular 
teeth into contact with the maxillary teeth. 

occluding centric relation record: obs a registration of 
centric relation made at the established occlusal ver- 
tical dimension (GPT-4). 

occlusal device: any removable artificial occlusal sur- 
face used for diagnosis or therapy affecting the re- 
lationship of the mandible to the maxillae. It may be 
used for occlusal stabilization, for treatment of tem- 
poromandibular disorders, or to prevent wear of 
the dentition. 

pantograph: n (1723) 1: an instrument used for copy- 
ing a planar figure to any desired scale. 2: in den- 
tistry, an instrument used to graphically record 
paths of mandibular movements and to provide in- 
formation for the programming instead of adjust- 
ment of an articulator. 

pantograph ic tracing: a graphic record of mandibular 
movement in three planes as registered by the stylii 
on the recording tables of a pantograph; tracings of 
mandibular movement recorded on plates in the 
horizontal and sagittal planes. 

preliminary cast: a cast formed from a preliminary im- 
pression for use in diagnosis or the fabrication of an 
impression tray. 

preliminary impression: a negative likeness made for 
the purpose of diagnosis, treatment planning, or the 
fabrication of a tray. 

preoperative wax-up: a dental diagnostic procedure in 
which planned restorations are developed in wax 
on a diagnostic cast to determine optimal clinical 
and laboratory procedures necessary to achieve the 
desired esthetics and function-also called diagnos- 
tic wax-up, preoperative waxing. 

protrusive interocclusal record: a registration of the 
mandible in relation to the maxillae when both 
condyles are advanced in the temporal fossa. 

reciprocal click: a pair of clicks emanating from the 
temporomandibular joint, one of which occurs dur- 
ing opening movements and the other during clos- 
ing movements. 



1 record: vb (14c) 1: to register data relating to specific 

conditions that exist currently or previously. 2: to 
register permanently by mechanical means (i.e., jaw 
relationships). 

2 record: n (14c) 1: an official document 2: a body of 

known or recorded facts about someone or some- 
thing. 

record base: an interim denture base used to support 
the record rim material for recording maxillo- 
mandibular records. 

semiadjustable articulator: an articulator that allows 
adjustment to replicate average mandibular move- 

mentS-alsO called Class 1 1 1 articulator 
stereographic record: an intra- or extraoral recording 
of mandibular movement. Viewed in three planes in 
which the registrations are obtained by engraving, 
milling, or burnishing the recording medium by 
means of studs, rotary instruments, styli, teeth, or 
abrasive rims. 



1. Mendez AJ: The influence of impression trays on 
the accuracy of stone casts poured from irre- 
versible hydrocoUoid impressions, J Prosthet 
Dent 54:383, 1985. 

2. Lim PF et al: Adaptation of finger-smoothed ir- 
reversible hydrocoUoid to impression surfaces, 
Int J Prosthodont 8:117, 1995. 

3. Khaknegar B, Ettinger RL: Removal time: a fac- 
tor in the accuracy of irreversible hydrocoUoid 
impressions, J Oral Rehabil 4:369, 1977. 

4. al-Omari WM et al: A microbiological investiga- 
tion foUowing the disinfection of alginate and 
addition cured silicone rubber impression mate 

rials, Eur J Prosthodont Restor Dent 6:97, 1998. 

5. Matyas J et al: Effects of disinfectants on dimen- 
sional accuracy of impression materials, J Pros- 
thet Dent 64:25, 1990. 

6. Johnson GH et al: Dimensional stability and de- 
tail reproduction of irreversible hydrocoUoid 
and elastomeric impressions disinfected by im 
mersion, J Prosthet Dent 79:446, 1998. 

7. Reisbick MH et al: Irreversible hydrocoUoid and 
gypsum interactions, int ] Prosthodont 10:7, 1997. 

8. Young JM: Surface characteristics of dental 
stone: impression orientation, J Prosthet Dent 
33:336, 1975. 

9. Palik JF et al: Accuracy of an earpiece face-bow, 

] Prosthet Dent 53:m0,l%5. 

10. PiehsHnger E et al: Computer simulation of oc- 
clusal discrepancies resulting from different 
mounting techniques, J Prosthet Dent 74:279, 1995. 

11. Adrien P, Schouver J: Methods for minimizing 
the errors in mandibular model mounting on an 
articulator, J Oral Rehabil 24:929, 1997. 



I 



Section i Planning and Preparation 



12. Dawson PE: Temporomandibular joint pain- 
dysfunction problems can be solved, J Prosthet 
Dent29:\m,W^. 

13. Tarantola GJ et al: The reproducibility of centric 
relation: a clinical approach, J Am Dent Assoc 
9:1245, 1997. 

14. McKee JR: Comparing condylar position re- 
peatability for standardized versus nonstan- 
dardized methods of achieving centric relation, 

J Prosthet Dent 11 \2^0, 1997. 

15. Lucia VO: A technique for recording centric rela- 
tion, J Pro^r/zer Denr 14:492, 1964. 

16. Gross M et al: The effect of three different 
recording materials on the reproducibility of 
condylar guidance registrations in three 
semi-adjustable articulators, J Oml Rehabil 
25:204, 1998. 

17. Wirth CG: Interocclusal centric relation records 
for articulator mounted casts. Dent Clin North 
Am 15:627,1971. 

18. Wirth CG, Aplin AW: An improved interocclusal 
record of centric relation, J Prosthet Dent 25:279, 
1971. 



19. Lundeen HC: Centric relation records: the effect 
of muscle action, J Prosthet Dent T^hlAA, 1914. 

20. Kepron D: Variations in condylar position rela- 
tive to central mandibular recordings. In 

LefkowitZ W, editor: Proceedings of the Second In- 
ternational Prosthodontic Congress, St Louis, 1979, 
Mosby, p 210. 

21. Teo CS, Wise MD: Comparison of retruded axis 
articular mountings with and without applied 
muscular force, /Ora/ Rehabil 8:363, 1981. 

22. Tamaki K et al: Reproduction of excursive tooth 
contact in an articulator with computerized ax- 
iography data, j Prosthet Dent 78:373, 1997. 

23. Lundeen HC, Wirth CG: Condylar movement 
patterns engraved in plastic blocks, J Prosthet 
Dent 30:866, 1973. 

24. Bell LJ, Matich JA: A study of the acceptabihty of 
lateral records by the Whip-Mix articulator, 

J Prosthet Dent 3^:22, 1977. 

25. Celar AG et al: Guided versus unguided 
mandibular movement for duplicating intraoral 
eccentric tooth contacts in the articulator, j Pros- 
thet Dent U\U, 199.9,.. 



m 



CHAPTER 




THREE 



Treatment Planning 




::-.vjiiiig8aiii?:iitaBanMniwaBn»^^«;;h'rrH'^in 



abutment 

Ante's law 

cantilever 

complete dentures 

crown 

fixed partial denture (FPD) 

nonrigid connectors 



removable partial denture 

(RPD) 
residual ridge 
span length 
supraclusion 
treatment sequence 



Treatment planning consists of formulating a logical 
sequence of treatment designed to restore the pa- 
tient's dentition to good health, with optimal func- 
tion and appearance. The plan should be presented 
in written form and should be discussed in detail 
with the patient. Good communication with the pa- 
tient is essential when formulating the plan. Most 
dental disorders can be corrected with several dif- 
ferent procedures; the patient's preferences are 
paramount in establishing a suitable treatment plan. 
An appropriate plan informs the patient about the 
present conditions, the extent of dental treatment 
proposed, the time and cost of treatment, and the 
level of home care and professional follow-up 
needed for success. In addition, before any irre- 
versible procedures are undertaken, the patient 
should understand that some details may need to be 
altered during the course of treatment. 

This chapter outlines the decisions that will be 
necessary when planning treatment for fixed 
prosthodontics. Foremost among these is the identifi- 
cation of patients' needs and their preferences, which 
must be correlated with the range of treatments 
available. For long-term success, when a fixed partial 
denture (FPD) is being considered, the abutment 
teeth must be carefully assessed. Finally, the treat- 
ment plan must be properly sequenced as part of an 
ongoing program of comprehensive dental care. 

IDENTIFICATION OF PATIENT NEEDS 

Successful treatment planning is based on proper 
identification of the patient's needs. If an attempt is 
made to have the patient conform to the "ideal" 



treatment plan rather than have the treatment plan 
conform to the patient's needs, success is unlikely. 
Frequently, several treatment plans are presented 
and discussed, each with advantages and disadvan- 
tages. Indeed, failing to explain and present alterna- 
tives may be legally negligent. 

Treatment is required to accomplish one or more 
of the following objectives: correcting an existing 
disease, preventing future disease, restoring func- 
tion, and improving appearance. 

CORRECTION OF EXISTING DISEASE 
Existing disease will be revealed during the clinical 
examination. The disease process can usually be ar- 
rested by identification and reduction of the initiat- 
ing factors, identification and improvement of the 
resistive factors, or both (Fig. 3-1). For example, oral 
hygiene instruction will reduce the amount of resid- 
ual plaque, an initiating factor, and thus will reduce 
the likelihood of further dental caries. It will also 
improve gingival health, and the resulting healthy 
tissue will be more resistant to disease. Additional 
fluoride intake (e.g., mouth rinses) is also recom- 
mended in a patient with a caries problem. Restora- 
tive care will replace damaged or missing tooth 
structure, but additional treatment is essential for 
controlling the disease that caused the damage. 




Fig. 3- 1 . Poor plaque control with dental caries. 



59 



I 



Section 1 Planning and Preparation 



PREVENTION OF FUTURE DISEASE 
The likelihood of future disease can be predicted 
by evaluating the patient's disease experience and 
by knowing the prevalence of the disease in the gen- 
eral population. Treatment should be proposed if 
future disease seems likely in the absence of such 
intervention. 

RESTORATION OF FUNCTION 

Although objective measurement may be difficult, 
the level of function is assessed during the exami- 
nation. Treatment may be proposed to correct im- 
paired function (e.g., mastication or speech). 

IMPROVEMENT OF APPEARANCE 

Patients often seek dental treatment because they 
are dissatisfied with their appearance. However, it 
is difficult to objectively assess dental esthetics. The 
dentist should develop expertise in this area and 
should be prepared to appraise the appearance of 
the patient's dentition and listen carefully to the pa- 
tient's views. If the appearance is far outside so- 
cially accepted values, the feasibility of corrective 
procedures should be brought to the patient's atten- 
tion. Long-term dental health should not be com- 
promised by unwise attempts to improve appear- 
ance. Patients should always be made aware of the 
possible adverse consequences of treatment. 



occlusion. The indirect procedure, used in making 
cast metal crowns (Fig. 3-2, B), facihtates the fabri- 
cation of more accurately shaped restorations. 

CAST METAL 

Cast metal crowns are fabricated outside the mouth 
and are cemented with a luting agent. To minimize 
exposure of the luting agent to oral fluids, a 
long-lasting restoration must have good marginal 
adaptation. The highly refined techniques for over- 
coming the problem of marginal fit also permit the 
manufacture of cast metal crowns with precisely 
shaped axial and occlusal surfaces. This ensures con- 
tinued periodontal health and good occlusal func- 
tion. The internal dimensions of a casting must seat 
without binding against the walls while remaining 
stable and not becoming displaced during function. 
Preparation design for cast metal restorations is crit- 
ical and is discussed in detail in Chapter 7. 

Intracoronal Restorations (Fig. 3-3). An intra- 
coronal cast metal restoration or inlay relies on the 
strength of the remaining tooth structure for sup- 
port and retention, just as a plastic restoration does. 
However, greater tooth bulk is needed to resist any 
wedging effect on the preparation walls. Therefore, 
this restoration is contraindicated in a significantly 
weakened tooth. When fabricated correctly, it is ex- 
tremely durable because of the strength and corro- 



AVAILABLE MATERIALS 
AND TECHNIQUES 

All existing restorative materials and techniques 
have limitations and cannot exactly match the prop- 
erties of natural tooth structure. Before the clinician 
selects the appropriate procedure, he or she should 
understand these limitations. This will help prevent 
an experimental approach to treatment. 

PLASTIC MATERIALS 

Plastic materials (e.g., silver amalgam or composite 
resin) are the most commonly used dental restora- 
tives. They allow simple and conservative restora- 
tion of damaged teeth. However, their mechanical 
properties are inferior to cast metal or metal- 
ceramic restorations. Their continued service de- 
pends on the strength and integrity of the remain- 
ing tooth structure. When the remaining tooth 
substance needs reinforcement, a cast metal restora- 
tion should be fabricated, usually with amalgam as 
the foundation or core (see Chapter 6). 

Large amalgam restorations (Fig. 3-2, A) are 
shaped or carved directly in the mouth. The great 
degree of difficulty associated with this direct ap- 
proach often results in defective contours and poor 




Fig. 3-2. A, The large amalgam restoration is hard to 
condense and contour accurately. B, The complete cast 
crown is stronger and can be shaped by an indirect proce- 
dure in the dental laboratory. 



Chapter 3 Treatment Planning 



I 



sion resistance of the gold casting alloy; in a tooth 
with a minimal proximal carious lesion, however, it 
usually requires greater removal of tooth structure 
than an amalgam preparation. Inlays do not have 
sufficient resistance or retention to be used as abut- 
ment retainers for fixed partial dentures. 

Extracoronal Restorations (Fig. 3-4). An extra- 
coronal cast metal restoration or crown encircles all 
or part of the remaining tooth structure. As such, it 
can strengthen and protect a tooth weakened by 
caries or trauma. To provide the necessary bulk of 
material for strength, considerably more tooth 
structure must be removed than for an intracoronal 




Fig. 3-3. The MOD inlay is generally contraindicated be- 
cause there is the risk of tooth fracture. However, it can be a 
very long-lasting restoration. These, placed in 1948, are still 
satisfactory after 52 years. 




restoration. The margins of an extracoronal restora- 
tion often must be near the free gingiva, which can 
make maintenance of tissue health difficult. Tooth 
preparation for an extracoronal restoration may be 
combined with intracoronal features (e.g., grooves 
and pinholes) to gain resistance and retention. 

METAL-CERAMIC 

Metal-ceramic restorations (Fig. 3-5) consist of a 
tooth-colored layer of porcelain bonded to a cast 
metal substructure. They are used when a complete 
crown is needed to restore appearance as well as 
function. Sufficient reduction of tooth structure is 
necessary to provide space for the bulk of porcelain 
needed for a natural appearance. Thus the prepara- 
tion design for a metal-ceramic crown is among the 
least conservative, although tooth structure can be 
conserved if only the most visible part of the 
restoration is veneered. 

The labial margins of a metal-ceramic restoration 
are often discernible and may detract from its appear- 
ance. They can be hidden by subgingival placement, 
although they then have the potential for increasing 
gingival inflammation; this should be avoided when 
possible.' Appearance can be improved by omitting 
the metal shoulder and making the labial margin in 
porcelain. As discussed in Chapter 24, this is a more 
demanding laboratory procedure. 

RESIN-VENEERED 

Resin- veneered restorations were popular before 
the metal-ceramic technique was fully developed. 



Fig. 3-4. A, Complete cast crowns. B, Partial veneer 
crown on a second premolar. 




Fig. 3-5. A, B, Metal- ceramic restorations. 



I 



SerCtion 1 Planning and Preparation 



but problems with wear and discoloration of the 
polymethyl methacrylate veneer (Fig. 3-6) limited 
their use to long-term provisional restorations. Cur- 
rent resin- veneer techniques' incorporate bis-GMA- 
based materials (bisphenol-A glycidyl dimethacry- 
lates), which have better physical properties than 
the earlier acrylic resins, and adhesive techniques to 
improve the bond to the supporting metal. 

FIBER-REINFORCED RESIN 

Advances in composite resin technology, especially 
the introduction of glass and polyethylene fibers, 
have prompted the use of indirect composite resin 
restorations for inlays, crowns, and FPDs. Excellent 
marginal adaptation and esthetic results are achiev- 
able (Fig 3-7), but because these are newer technolo- 
gies, little is known about their longer-term perfor- 
mance (see Chapter 27). 

COMPLETE CERAMIC 

Crowns, inlays, and laminate veneers made entirely 
of dental porcelain can be the most esthetically 
pleasing of all fixed restorations (Fig. 3-8). Draw- 
backs include a comparative lack of strength and the 
difficulties associated with achieving an acceptable 
marginal fit. The current focus in improving strength 
lies with either veneering a high- strength alumina, 
zirconia, or spinel core with a more translucent 
porcelain or using a leucite-reinforced translucent 




Fig . 3-6 . Worn acrylic resin veneer. 



material" '' (see Chapter 25). Complete ceramic 
restorations are fabricated by an indirect technique 
and generally retained with composite resin. Acid 
etching is used to provide retention "keys." 

FIXED PARTIAL DENTURES 

An FPD (Fig. 3-9) is often indicated where one or 
more teeth require removal or are missing. Such 
teeth are replaced by pontics that are designed to ful- 
fill the functional and often the esthetic requirements 
of the missing teeth (see Chapter 19). Pontics are 
connected to retainers, which are the restorations on 
prepared abutment teeth. 

All the components of an FPD are fabricated and 
assembled in the laboratory before cementation in 
the mouth. This requires precise alignment of tooth 
preparations. Because unseating forces on individual 
retainers can be considerable, highly retentive 
restorations are essential. The predictable long-term 
success of an FPD is ensured by controlHng the mag- 
nitude and direction of forces and by making sure the 
patient practices appropriate oral hygiene measures. 

IMPLANT-SUPPORTED PROSTHESES 

Single or multiple missing teeth can be replaced 
with an implant- supported prosthesis (Fig. 3-10). 
For the successful "osseointegrated" technique, the 
bone is atraumatically drilled to receive precisely 
fitting titanium cyhnders . 13 These are left in place 
without loading for some months until they are in- 
vested with bone. Only then are function and es- 
thetics restored with a prosthesis (see Chapter 13). 

REMOVABLE PARTIAL DENTURES 

A removable partial denture (RPD) (Fig. 3-11) is 
designed to replace missing teeth and their sup- 
porting structures. Forces applied to a well-de- 
signed prosthesis are distributed to the remaining 
teeth and the residual alveolar ridges. These forces 
are most accurately controlled if the abutment teeth 
are provided with fixed cast restorations that have 
carefully contoured guide planes and rest seats (see 
Chapter 20). 





Fig . 3-7 . Fiber-reinforced fixed partial denture. 



Fig. 3-8. Complete ceramic restoration. 



Abutment tooth 




Abutment 
prepjaration 





Part) a I -coverage ™""^^ Connector 
retainer 



Fig. 3-9. A, A three-unit FPD showing the main components. B, The pontic rigidly attached to crowns 
on the abutment teeth. The connectors should occupy the normal interproximal contact area and be large 
enough for strength but not so large as to impede plaque control. 




Fig. 3-10. Three-unit FPD supported by two dental implants. 



Fig. 3-11. The component parts of an RPD. 




I 



Section 1 Planning and Preparation 



I 





Fig. 3-1 2. Special planning is required when a combination of a complete maxillary denture is 
planned opposing a fixed mandibular prosthesis. In general, a trial maxillary denture is indicated so the 
fixed prosthesis can be fabricated to a well-aligned occlusal plane. A, Preoperative appearance. B, Trial 
denture articulated with diagnostic waxing. C and D, Completed restoration. 

(Courtesy Dr. K.A. Laurell.) 



COMPLETE DENTURES 

Some of the difficulties encountered with complete 
dentures relate to the lack of denture stability and a 
gradual loss of supporting bone. Stability is en- 
hanced if the denture has a carefully designed oc- 
clusion. Problems with stability can be especially se- 
vere when the mandibular incisors are the only 
teeth retained, with ensuing damage to the oppos- 
ing premaxilla," although any treatment plan that 
involves a complete denture opposing fixed restora- 
tions requires careful planning of the occlusion (Fig. 
3-12). For selected patients, providing an overden- 
ture that rests on endodontically treated roots may 
help preserve the residual ridge and enhance the 
stability of the complete denture.'-' 

TREATMENT OF TOOTH LOSS 

A treatment plan involving fixed prosthodontics 
will generally include the replacement of missing 
teeth. Most teeth are lost as a result of dental caries 
or periodontal disease. More rarely they may be 
congenitally absent or lost as a result of trauma or 
neoplastic disease. 

DECISION TO REMOVE A TOOTH 
The decision to remove a tooth is part of the treat- 
ment-planning process and is made after assessing 
the advantages and disadvantages associated with re- 
tention of the tooth. Sometimes it is possible to retain 
a tooth with an apparently hopeless prognosis by us- 




Fig. 3-1 3. Poor treatment planning. The displaced 

premolar should never have been restored under these 

circumstances. 

(Courtesy Dr. P.B. Robinson.) 



ing highly specialized and complex techniques. At 
other times, removing the tooth will be the treatment 
of choice. A decision about replacing a missing tooth 
is best made at the time its removal is recommended, 
rather than months or years after the fact (Fig. 3-13). 

CONSEQUENCES OF REMOVAL WITHOUT REPLACEMENT 
The stability of an individual tooth depends on a bal- 
ance of the forces exerted on that tooth by the adja- 
cent and opposing teeth and supporting tissues and 
by the soft tissues of the cheeks, lips, and tongue. 
When a single tooth is not replaced, this balance is 
upset (Fig. 3-14). The consequences may be supra- 



Chapter 3 Treatment Planning 



I 




Over time, loss of arch 
integrity will result in 
tooth movement. 



Fig. 3-14. Loss of a mandibular first molar not replaced with an 
FPD. The typical consequences are supraclusion of opposing teeth 
(1), tilting of adjacent teeth (2), and loss of proximal contacts (3). 

(Redrawn from Rosenstiel SF: In Rayne J, editor: General dental treat- 
ment, London, 1983, Kluwer Publishing.) 



elusion of the opposing tooth or teeth, tilting o€ the 
adjacent teeth, and loss of proximal contact (with re- 
sulting disturbances in the health of the supporting 
structures and the occlusion). Although simple re- 
placement of the missing tooth at this late stage may 
prevent further disruption, it may be insufficient to 
return the dentition to full health. Extended treat- 
ment plans, including orthodontic repositioning and 
additional cast restorations (to correct the disturbed 
occlusal plane), may be needed to compensate for the 
lack of treatment at the time of tooth removal. 



SELECTION 



OF ABUTMENT TEETH 



Whenever possible, FPDs should be designed as sim- 
ply as possible, with a single well-anchored retainer 
fixed rigidly at each end of the pontic. The use of 
multiple splinted abutment teeth, nonrigid connec- 
tors, or intermediate abutments makes the procedure 
much more difficult, and often the result compro- 
mises the long-term prognosis (Fig. 3-15). 

REPLACEMENT OF A SINGLE MISSING TOOTH 
Unless bone support has been weakened by ad- 
vanced periodontal disease, a single missing tooth 



can almost always be replaced by a three-unit FPD 
having one mesial and one distal abutment tooth. 
An exception is when the FPD is replacing a maxil- 
lary or mandibular canine. Under these circum- 
stances, the small anterior abutment tooth needs to 
be splinted to the central incisor to prevent lateral 
drift of the FPD. 

Cantilever Fixed Partial Dentures. FPDs in 
which only one side of the pontic is attached to a re- 
tainer are referred to as cantilevered. An example 
would be a lateral incisor pontic attached only to an 
extracoronal metal-ceramic retainer on a canine. 
Their use remains popular because some of the dif- 
ficulties encountered in making a three-unit FPD 
are lessened. Also, many clinicians are reluctant to 
prepare an intact central incisor, preferring instead 
to use a cantilever. 

However, the long-term prognosis of the single- 
abutment cantilever is poor. 16 Forces are best toler- 
ated by the periodontal supporting structures when 
directed in the long axes of the teeth. ^^ This is the 
case when a simple three-unit FPD is used. A can- 
tilever will induce lateral forces on the supporting 
tissues, which may be harmful and lead to tipping. 



I 



Section 1 Planning and Preparation 




^^^^' '^'Vjl 




Fig. 3-15. A to C, Congenitally missing lateral incisors replaced with two simple three-unit FPDs. 
D to F, This patient had a missing canine as well as two congenitally missing laterals. Here, there is a 
much greater restorative challenge than in A, requiring an eight-unit prosthesis. 



rotation, or drifting of the abutment (Fig. 3-16). Lab- 
oratory analysis's" has confirmed the potential 
harmful nature of such fixed partial dentures. How- 
ever, clinical experience with resin-retained FPDs 
has suggested that cantilever designs may be pre- 
ferred, especially since readhesion after failure is 
greatly facilitated and often leads to predictable 
long-term success20 (see Chapter 26). 

When multiple missing teeth are replaced, can- 
tilever FPDs have considerable application (see p. 70). 
The harmful tipping forces are resisted by multiple 
abutment teeth, and movement of the abutments is 
unlikely. Cantilevers are also successfully used with 
implant- supported prostheses (see Chapter 13). 

Assessment of Abutment Teeth. Considerable 
time and expense are spared, and loss of a patient's 



confidence can be avoided, by thoroughly investi- 
gating each abutment tooth before proceeding 
with tooth preparation. Radiographs are made, 
and pulpal health is assessed by evaluating the re- 
sponse to thermal and electrical stimulation. Exist- 
ing restorations, cavity liners, and residual caries 
are removed21 (preferably under a rubber dam), 
and a careful check is made for possible pulpal ex- 
posure. Teeth in which pulpal health is doubtful 
should be endodontically treated before the initia- 
tion of fixed prosthodontics. Although a direct 
pulp cap may be an acceptable risk for a simple 
amalgam or composite resin, conventional en- 
dodontic treatment is normally preferred for cast 
restorations, especially where the later need for en- 
dodontic treatment would jeopardize the overall 
success of treatment. 



Chapter 3 Treatment Planning 



I 




To be successful, single 
abutment cantilevers 
require a very favorable 
occlusion- 



Rotation 

Fig. 3-1 6. A, Forces applied to a cantilever FPD are resisted on only one side, leading to imbalance. 
Vertical forces can cause tipping, and horizontal forces, rotation, of abutment teeth. B, By including both 
adjacent teeth in the prosthesis, it is possible to resist forces much better since the teeth have to be 
moved bodily rather than merely rotated or tipped. 

(Redrawn from Rosenstiel SF: In Rayne J, editor: General dental treatment, London, 1983, Kluwer Publishing.) 




Endodontically Treated Abutments. If a tooth 
is properly treated endodontically, it can serve well 
as an abutment with a post and core foundation for 
retention and strength (see Chapter 12). Failures oc- 
cur, however, particularly on teeth with short roots 
or little remaining coronal tooth structure. Care is 
needed to obtain maximum retention for the post 
and core. Sometimes it is better to recommend re- 
moval of a badly damaged tooth rather than to at- 
tempt endodontic treatment. 

Unrestored Abutments. An unrestored, caries- 
free tooth is an ideal abutment. It can be prepared 
conservatively for a strong retentive restoration with 
optimum esthetics (Fig. 3-17). The margin of the re- 
tainer can be placed without modifications to ac- 
commodate existing restorations or caries. In an 
adult patient, an unrestored tooth can be safely pre- 
pared without jeopardizing the pulp as long as the 
design and technique of tooth preparation are wisely 
chosen. Certain patients are reluctant to have a per- 
fectly sound tooth cut down to provide anchorage 
for a fixed partial denture. In these cases, the overall 
dental health of the patient should be emphasized 
rather than looking at each tooth individually. 

Mesially Tilted Second Molar. Loss of a per- 
manent mandibular first molar to caries early in life 
is still relatively common (Fig. 3-18). If the space is 
ignored, the second molar will tilt mesially, espe- 




Fig. 3-1 7. A, Unrestored abutment teeth can be pre- 
pared for conservative retainers. B, An esthetic FPD replac- 
ing a maxillary incisor. 



I 



Section 1 Planning and Preparation 



B 




Malali^menl of iSbutmenb 
can result in excessive tooth 
reduction. 




Fig. 3-18. A, Early loss of a mandibular first molar with mesial tilting and drifting of the second and 
third molars. B, A conventional three-unit FPD will fail because its seating is prevented by the third molar. 
C, A modified preparation design can be used on the distal abutment. D, A better treatment plan would be 
to remove the third molar and upright the second molar orthodontic ally before fabricating an FPD. 

(Redrawn front Rosenstiel SF: In Ray ne J, editor: General dental treatment, London, 1983, Kluwer Publishing.) 



Chapter 3 Treatment Planning 



I 



daily with eruption of the third molar. It then be- 
comes difficult or impossible to make a satisfactory 
fixed partial denture, because the positional rela- 
tionship no longer allows for parallel paths of inser- 
tion without interference from the adjacent teeth. 
In such circumstances, an FPD is sometimes made 
with modified preparation designs or with a non- 
rigid connector, or a straightforward solution 22 may 
be considered: uprighting the tilted abutment or- 
thodontically with a simple fixed appliance. How- 
ever, the problem can be avoided altogether if a 
space-maintainer appliance (Fig. 3-19) is fabricated 
when the first molar is removed. This device may be 
as simple as a square section of orthodontic wire 
bent to follow the edentulous ridge and anchored 
with small restorations in adjacent teeth. 

REPLACEMENT OF SEVERAL MISSING TEETH 

Fixed prosthodontics becomes more difficult when 
several teeth must be replaced. Problems will be en- 
countered when restoring a single long, uninter- 
rupted edentulous area or multiple edentulous ar- 
eas with intermediate abutment teeth (Fig. 3-20), 
especially when anterior and posterior teeth are to 
be replaced with a single fixed prosthesis. Underes- 
timation of the problems involved in extensive 
prosthodontics can lead to failure. One key to en- 
suring a successful result is to plan the prostheses 
by waxing the intended restorations on articulated 
diagnostic casts. This is essential for complex fixed 
prosthodontic treatments, particularly where an ir- 
regular occlusal plane is to be corrected, the vertical 
dimension of occlusion is to be altered, an im- 
plant-supported prosthesis is recommended, or a 
combination of fixed and removable prostheses are 
to be used. The precise end point of such compli- 




Fig. 3-19. Square section orthodontic wire can be used 
as a simple stabilizing appliance to prevent drifting of abut- 
ment teeth after exodontia. The wire is retained by placing 
small restorations. As an alternative, orthodontic bands can 
be used as the retainer. NOTE: These simple stabihzers do 
not prevent supraeruption of opposing teeth; in areas 
where this is anticipated, a provisional FPD is needed. 



cated treatments can be far from evident, even to an 
experienced prosthodontist (see Fig. 2-39). 

Overloading of Abutment Teeth. The ability of 
the abutment teeth to accept applied forces without 
drifting or becoming mobile must be estimated and 
has a direct influence on the prosthodontic treat- 
ment plan. These forces can be particularly severe 
during parafunctional grinding and clenching (see 
Chapter 4), and the need to eliminate them becomes 
obvious during the restoration of such a damaged 
dentition. Although it may be hoped that a well- 
reconstructed occlusion will reduce the duration 
and strength of any parafunctional activity, there is 
little scientific evidence to support this. It is unwise 
to initiate treatment on the assumption that new 
restorations will reduce parafunctional activity, un- 
less this has been demonstrated with treatment ap- 
pliances over a significant period .23 

Direction of Forces. Whereas the magnitude 
of any applied force is difficult to regulate, a 
well-fabricated fixed partial denture can distribute 
these forces in the most favorable way, directing 
them in the long axis of the abutment teeth. Poten- 
tially damaging lateral forces can be confined to the 
anterior teeth, where they are reduced by the longer 
lever arm (see Chapter 4). 

Root Surface Area. The root surface area of 
potential abutment teeth must be assessed when 
planning treatment for fixed prosthodontics. 
Ante" suggested in 1926 that it was unwise to pro- 
vide a fixed partial denture when the root surface 
area of the abutment was less than the root surface 
area of the teeth being replaced; this has been 
adopted and reinforced by other authors25-27 
Ante's law. Average values for the root surface area 
of permanent teeth are given in Table 3-1.28 As an ex- 
ample of Ante's law, consider the patient who has 
lost a first molar and second premolar (Fig. 3-21). In 
this situation, a four-unit FPD is an acceptable risk, 
as long as there has not been bone loss from peri- 
odontal disease, because the second molar and first 
premolar abutments have root surface areas ap- 
proximately equal to those of the missing teeth. If 
the first molar and both premolars are missing, 
however, an FPD is not considered a good risk be- 
cause the missing teeth have a greater total root sur- 
face area than the potential abutments. 

Nyman and Ericsson, 29 however, cast doubt on 
the validity of Ante's law by demonstrating that 
teeth with considerably reduced bone support can 
be successfully used as fixed partial denture abut- 
ments. The majority of the treatments presented by 



I 



Section i Planning and Preparation 




Cantilever 
pontic 

Fig. 3-20. A, A five-unit FPD replacing the maxillary first molar and first premolar. The middle abut- 
ment can act as a fulcrum during function, with possible unseating of one of the other abutments. To be 
successful, this type of FPD needs extremely retentive retainers. B, An alternative approach is a nonrigid 
dovetail connector between the molar pontic and the second premolar. C, Where periodontal support is 
adequate, a much simpler approach would be to cantilever the first premolar pontic. 

(Redrawn from Rosenstiel SF: In Ray ne J, editor: General dental treatment, London, 1983, Kluwer Publishing.) 



Chapter 3 Treatment Planning 



I 



Ante's law is useful for 
determining the prognosis 
of fixed partial dentures. 




Fig. 3-21 . To assess the support of a fixed partial den- 
ture, Ante's law has been invoked. It proposes a relation- 
ship between the root surface areas of the missing teeth and 
those of the potential abutment teeth. (The numbers repre- 
sent root surface area percentages.) If the first molar (22) 
and second premolar (11) are missing, the abutments for a 
four-unit FPD will have slightly greater total root surface 
area (34%) than the teeth being replaced. Then, in the ab- 
sence of other detrimental factors, an FPD's prognosis will 
be favorable. However, if the first premolar (12) is also 
missing, the loss of potential abutment root surface area 
will comprise 45%, whereas the remaining abutments have 
only 36%, which is much less favorable. 



of Abutm- 



Maxiiiarv 

Central 

Lateral 

Canine 

First premolar 

Second premoior 

First molar 

Second molar 

Mandibular 

Central 

Lateral 

Canine 

first premolar 

Second premolar 

Firist molar 

Second moJar 



TABLE 3*1 





Percentage Root SurK^ce 




Aru^i in Qundrant 


204 


10 


179 


9 


273 


14 


234 


12 


220 


11 


433 


22 


431 


22 




154 


8 


168 


9 


268 


15 


180 


10 


207 


11 


431 


24 


426 


23 



Data from Jepsen A: Ada Odo?ftoi Scmid 21:35, 1%3. 

these authors had an abutment root surface area less 
than half that of the replaced teeth, and there was 
no loss of attachment after 8 to 11 years. They at- 
tributed this success to meticulous root planing dur- 
ing the active phase of treatment, proper plaque 
control during the observed period, and the oc- 




Fig. 3-22. A, A misaUgned abutment tooth may be diffi- 
cult or impossible to prepare for an FPD abutment and pro- 
vides poor support. B and C, Where possible, this should 
be corrected with orthodontic treatment before restoration. 

(Courtesy Dr. G. Gruendeman.) 

clusal design of the prostheses. Others have con- 
firmed that abutment teeth with limited periodontal 
bone can successfully support fixed prostheses .30,31 

Root Shape and Angulation. When tooth sup- 
port is borderline, the shape of the roots and their 
angulation should be considered. A molar with di- 
vergent roots will provide better support than a mo- 
lar with conical roots and little or no interradicular 
bone. A single-rooted tooth with an elliptic cross- 
section will offer better support than a tooth with 
similar root surface area but a circular cross-section. 
Similarly, a well-aligned tooth will provide better 
support than a tilted one. Alignment can be im- 
proved with orthodontic uprighting (Fig. 3-22). 

Periodontal Disease. After horizontal bone 
loss from periodontal disease, the PDL-supported 
root surface area can be dramatically reduced ^^ Be- 
cause of the conical shape of most roots (Fig. 3-23), 
when one third of the root length has been exposed, 
half the supporting area is lost. In addition, the 
forces applied to the supporting bone are magnified 
because of the greater leverage associated with the 
lengthened clinical crown. Thus potential abutment 



I 



Section 1 Planning and Preparation 




Fig. 3-23. A, Because of the conical shape of most roots, the 
actual area of support (A) diminishes more than might be ex- 
pected from the height of the bone (H). In addition, the center 
of rotation (R) moves apically and the lever arm (L) increases, 
magnifying the forces on the supportive structure. B, A fixed 
partial denture replacing a maxitlary first molar. The first pre- 
molar is an abutment providing additional stabilization for 
this FPD on abutment teeth with compromised bone support. 
(A redrawn from Roseustiel SF: In Rayne J, editor: General dental 
treatment, London, 1983, Kluwer Publishing.) 



he deceptive. A little can 
result in a considerable 
loss of bone support be- 
cause of root moqphofogy. 





Fig. 3-24. A, Supragingival margins and large gingival 
embrasures facilitate plaque control in a periodontally com- 
promised patient. B, Poor prosthetic contours and margins 
have contributed to this failure. 



teeth need very careful assessment where signifi- 
cant bone loss has occurred. 

In general, successful fixed prostheses can be fab- 
ricated on teeth with severely reduced periodontal 
support, provided the periodontal tissues have been 
returned to excellent health, and long-term mainte- 
nance has been ensured 33 (Fig. 3-24). When exten- 
sive reconstruction is attempted without complete 
control over the health of the periodontal tissues, 
the results can be disastrous. 

Healthy periodontal tissues are a prerequisite for 
all fixed restorations. If the abutment teeth have 
normal bone support, an occasional lapse in plaque 
removal by the patient is unlikely to affect the 
long-term prognosis. However, when teeth with se- 
vere bone loss resulting from periodontal disease 
are used as abutments, there is very little tolerance. 
It then becomes imperative that excellent plaque - 
removal technique be implemented and maintained 
at all times. 

Span Length. Excessive flexing under occlusal 
loads may cause failure of a long-span fixed partial 
denture (Fig. 3-25). It can lead to fracture of a porce- 
lain veneer, breakage of a connector, loosening of a 
retainer, or an unfavorable soft tissue response and 
thus render a prosthesis useless. All FPDs flex 
slightly when subjected to a load- the longer the 
span, the greater the flexing. The relationship be- 



Chapter 3 Treatment Planning 



I 




Fig. 3-25. Failure of a long-span fixed partial denture. 




Excessive span length is 
a common contraindication 
for fixed partial dentures. 



Fig. 3-26. The deflection of a fixed partial denture is proportional to the cube of the length of its span. 
A, A single pontic will deflect a small amount (D) when subjected to a certain force (F). B, Two pontics will 
deflect 23 times as much (8 d) to the same force. C, Three pontics will deflect 33 times as much (27 D). 



tween deflection and length of span is not simply 
linear but varies with the cube of the length of the 
span. Thus, other factors being equal, if a span of a 
single pontic is deflected a certain amount, a span of 
two similar pontics will move 8 times as much, and 
three will move 27 times as much^^ (Fig. 3-26). 

Replacing three posterior teeth with an FPD 
rarely has a favorable prognosis, especially in the 
mandibular arch. Under such circumstances it is 
usually better to recommend an implant- supported 
prosthesis or a removable partial denture. 

When a long- span FPD is fabricated, pontics and 
connectors should be made as bulky as possible to 



ensure optimum rigidity without jeopardizing gin- 
gival health. In addition, the prosthesis should be 
made of a material that has high strength and rigid- 
ity (see Chapter 16). 

Replacing Multiple Anterior Teeth. Special 
considerations in this situation include problems 
with appearance and the need to resist laterally di- 
rected tipping forces. 

The four mandibular incisors can usually be re- 
placed by a simple fixed partial denture with retain- 
ers on each canine. It is not usually necessary to in- 
clude the first premolars. If a lone incisor remains, it 



I 



Section 1 Elanning and Preparation 



should be removed because its retention will unnec- 
essarily complicate the design and fabrication of 
the FPD and can jeopardize the long-term result. 
Mandibular incisors, because of their small size, gen- 
erally make poor abutment teeth. It is particularly 
important not to have overcontoured restorations on 
these teeth because plaque control will be nearly im- 
possible. Thus the clinician may have to make a 
choice between (1) compromised esthetics from too 
thin a ceramic veneer and (2) pulpal exposure dur- 
ing tooth preparation. A third alternative would be 
selective tooth removal. 

The loss of several maxillary incisors presents a 
much greater problem in terms of restoring appear- 
ance and providing support. Because of the curva- 
ture of the arch, forces directed against a maxillary 
incisor pontic will tend to tip the abutment teeth. 
Unlike the mandibular incisors, the maxillary in- 
cisors are not positioned in a straight line (particu- 
larly in patients with narrow or pointed dental 
arches). Tipping forces must be resisted by means of 
two abutment teeth at each end of a long span ante- 
rior FPD. Thus, when replacing the four maxillary 
incisors, the clinician should generally use the ca- 
nines and first premolars as abutment teeth.36 

There may be considerable difficulty in achieving 
a good appearance when several maxillary incisors 
are being replaced with a fixed partial denture. Ob- 
taining the best tooth contours and position for ap- 
pearance and phonetics can be a challenge. A good 
attempt can be made with the diagnostic waxing 
procedure, evaluating any esthetic problems. As 
treatment progresses, a provisional restoration is 
provided (see Chapter 15). This may be used to test 
appearance and phonetics. It may also be readily 
shaped and modified to suit the patient, and the fi- 
nal restoration can be made as a copy of it, thereby 
avoiding any embarrassing misunderstandings 
when the finished fixed prosthesis is delivered. 

If anterior bone loss has been severe, as can hap- 
pen \vhen teeth are lost due to trauma or 
periodontal disease, there may be a ridge defect 
(Fig. 3-27). In these patients, a removable partial 
denture should be considered, especially when 
the person has a high smile line, since a fixed partial 
denture generally replaces only the missing tooth 
structure, not the supporting tissues. Again, a pro- 
visional restoration may help the patient determine 
the most appropriate treatment. A surgical ridge 
augmentation procedures? may also be an option, al- 
though the results can be unpredictable. 

INDICATIONS FOR REMOVABLE PARTIAL DENTURES 

Whenever possible, edentulous spaces should be re- 
stored with fixed rather than removable partial den- 




Fig. 3-27. This patient lost two incisors in an accident. 
Considerable alveolar bone has also been lost. An aesthetic 
fixed prosthesis would be very difficult or impossible to 
fabricate without surgical ridge augmentation. 

(Courtesy Dr. N. Arehambo.) 




Fig. 3-28. A removable partial denture replacing the 
mandibular right first and second molars. 



tures. A well-fabricated FPD will provide better 
health and better function than an RPD and is pre- 
ferred by most patients. Under the following cir- 
cumstances, however, a removable partial denture 
is indicated: 

1. Where vertical support from the edentulous 
ridge is needed; for example, in the absence 
of a distal abutment tooth (Fig. 3-28) 

2. Where resistance to lateral movement is 
needed from contralateral teeth and soft tis- 
sues; for example, to ensure stability with a 
long edentulous space 

3. When there is considerable bone loss in the 
visible anterior region and an FPD would 
have an unacceptable appearance (Fig. 3-29) 

Multiple edentulous spaces often are best re- 
stored with a combination of fixed and removable 
partial dentures (Fig. 3-30). 



Chapter 3 Treatment Planning 



I 




Fig. 3-29. 

an FPD. 



Where there has been considerable bone loss, an RPD has a more natural appearance than 



Fixed 




dent 






Fixed 

partial 
denture 



Miiiimizing the number of 
modification spaces in a 
removable partial denture 
is often helpful. 



Fig. 3-30. Treatment planning for multiple edentulous spaces. A combination of fixed and removable 
prostheses may provide the best replacement when several teeth are missing. In the maxillary arch, the 
missing lateral has been restored with a simple three-unit FPD, which is more easily cleaned than an 
RPD. In the mandibular arch, the single remaining premolar is splinted to the canine with a three-unit 
FPD. An RPD that fits around a lone-standing premolar usually does not have a good prognosis. 

(Redrawn from Rosenstiel SF: In Rayne J, editor: General dental treatment, London, 1983, Kluwer Publishing.) 



I 



Section i Planning and Preparation 

^SEQUENCE OF TREATMENT 

When patient needs have been identified and the 
appropriate corrective measures have been deter- 
mined, a logical sequence of steps must be decided 
on-including the treatment of symptoms, stabi- 
lization of deteriorating conditions, definitive ther- 
apy, and a program of follow-up care. The impor- 
tance of proper sequencing is stressed, since 
mistakes can lead to compromised effort or unnec- 
essary and expensive remakes. 

TREATMENT OF SYMPTOMS 

The relief of discomfort accompanying an acute 
condition is a priority item in planning treatment 
(Fig. 3-31). Discomfort can be due to one or more of 
the following: a fractured tooth or teeth, acute pul- 
pitis, acute exacerbation of a chronic pulpitis, dental 
abscess, an acute pericoronitis or gingivitis, and 
myofascial pain dysfunction. 

The clinician needs only sufficient diagnostic in- 
formation to ascertain the nature of a particular con- 
dition and to form a diagnosis; treatment is insti- 
tuted without delay. A full examination is neither 
desirable nor generally possible until the symptoms 
of the acute condition have been addressed. 

Urgent Treatment of Nonacute Problems. For- 
tunately, most potential candidates for fixed 
prosthodontics do not seek treatment for acute con- 
ditions; however, they may have a specific problem 
that should receive immediate attention, such as a 
lost anterior crown, a cracked or broken porcelain 
veneer, or a fractured removable prosthesis (Fig. 
3-32). 

STABILIZATION OF DETERIORATING CONDITIONS 
The second phase of treatment involves stabilizing 
conditions such as dental caries or periodontal dis- 
ease by removing the etiologic factors, increasing 
the patient's resistance, or doing both. 




Dental Caries. Treatment of carious lesions is 
approached in a conventional manner, and the teeth 
are restored with properly contoured plastic materi- 
als. These may serve as a foundation for fixed cast- 
ings during a subsequent phase of treatment (see 
Chapter 6). However, cast restorations are best 
avoided in a patient with active caries because the 
results of such extensive treatment would be jeop- 
ardized by recurrence of the disease. This can be 
prevented by a combination of dietary advice, oral 
hygiene measures, and fluoride treatment. 

Periodontal Disease. Chronic periodontitis 
with continuing irreversible bone loss should be 
treated as early as possible by effective daily plaque 
control. The proper removal of plaque is possible 
only if the teeth are smooth and their contours allow 
unimpeded access to the gingival sulci. Therefore, 
the following are essential (Fig. 3-33): 

• Replacement of defective restorations 

• Removal of carious lesions 

• Recontouring of overcontoured crowns (espe- 
cially near furcation areas) 

• Proper oral hygiene instruction adequately im- 
plemented at home 

DEFINITIVE THERAPY 

When the stabilization phase has been completed, 
successful elective long-term treatment aimed at 
promoting dental health, restoring function, and 
improving appearance can begin. On occasion, this 
will take considerable time. Several therapeutic pro- 
posals may be applicable to a single patient and 
may range in complexity from minimum restorative 
treatment with regular maintenance to full mouth 
prosthodontic reconstruction preceded by orthog- 
nathic surgery and orthodontic treatment. The ad- 
vantages and disadvantages of each should be thor- 
oughly explained to the patient, with diagnostic 
casts and waxings used as guides. When a definitive 
plan is established, it should attempt to minimize 
the possibility of having to repeat earlier treatment 
if problems later occur. Usually oral surgical proce- 
dures are scheduled first, followed by periodontics. 




Fig. 3-31 . Swelling from an acute periapical abscess. 
(Courtesy Dr. P.B. Robinson.) 



Fig. 3-32. For both appearance and comfort, fractured 
porcelain often necessitates urgent treatment. 



Chapter 3 Treatment Planning 



I 



endodontics, orthodontics, fixed prosthodontics, 
and finally, removable prosthodontics. 

Oral Surgery. The treatment plan should allow 
time for healing and ridge remodeling. Therefore, 
teeth with a hopeless prognosis, unerupted teeth, 
and residual roots and root tips should be removed 
early. All preprosthetic surgical procedures (e.g., 
ridge contouring) should be undertaken during the 
early phase of treatment. 

Periodontics. Most periodontal procedures 
should (or will) have been accomplished as part of 
the stabilization phase of treatment. Any surgery, 
pocket elimination, mucogingival procedure, 
guided tissue regeneration, or root resection is per- 
formed at this time (see Chapter 5). 

Endodontics. Some endodontic treatment may 
have been accomplished as part of the relief of dis- 
comfort and stabilization of conditions. Elective en- 
dodontics may be needed to provide adequate 
space for a cast restoration or to provide retention 
for a badly damaged or worn tooth. 

If a tooth with doubtful pulpal health is to be 
used as an abutment for an FPD, it should be en- 
dodontically treated prophylactically, despite the 
consideration that periodic recall may be more ap- 
propriate treatment if a single restoration is 
planned. 

Orthodontics. Minor orthodontic tooth move- 
ment is a common adjunct to fixed prosthodontics. 
A tooth can be uprighted, rotated, moved laterally, 
intruded, or extruded to improve its relationship 
before fixed prosthodontic treatment. Orthodontics 
should always be considered when a treatment plan 
is being proposed, especially if tooth loss has been 
neglected and drifting has occurred. 




Fig. 3-33. Overhangs and defective restorations impede 
proper plaque control and should be corrected as part of 
the stabilization process. 



Fixed Prosthodontics. Fixed prosthodontic 
treatment is initiated only after the preceding 
modalities have been completed. This will permit 
modification of the original plan if unforeseen diffi- 
culties surface during treatment. For example, a 
tooth scheduled for endodontic treatment might 
prove to be untreatable, requiring considerable 
modification of the restorative treatment plan. 

Occlusal Adjustment. Occlusal adjustments 
are often necessary before the initiation of fixed 
prosthodontics. Where extensive fixed prosthodon- 
tics is to be provided, an accurate and well-tolerated 
occlusal relationship may be obtainable only if a 
discrepancy between intercuspal position and cen- 
tric relation is eliminated first (see Chapter 4). When 
less extensive treatment is planned, it may be ac- 
ceptable to conform the fixed prosthesis to the exist- 
ing occlusion, provided the patient is functioning 
satisfactorily. However, any supraeruption or drift- 
ing should be corrected rather than be allowed to 
compromise the patient's occlusal scheme. 

Anterior Restorations. If both anterior and 
posterior teeth are to be restored, the anterior teeth 
are usually done first because they influence the 
border movements of the mandible and thus the 
shape of the occlusal surfaces of the posterior teeth 
(see Chapter 4). If the posterior teeth were restored 
first, a subsequent change in the lingual contour of 
the anterior teeth could require considerable adjust- 
ment of the posterior restorations. 

Posterior Restorations. Restoring opposing 
posterior segments at the same time is often advan- 
tageous. This permits the development of an efficient 
occlusal scheme through the application of an addi- 
tive wax technique (see Chapter 18). One side of the 
mouth should be completed before the other side is 
treated; restoring all four posterior segments at the 
same time might lead to considerably more compli- 
cations for the patient and dentist, including fracture 
or breaking of provisional restorations, discomfort 
with bilateral local anesthesia, and difficulties in con- 
firming the accuracy of jaw relationship recordings. 

Complex Prosthodontics. Carefully planned 
treatment sequencing is particularly important 
when complex prosthodontic treatments involving 
alteration of the vertical dimension or a combina- 
tion of fixed and removable prostheses are required. 
One recommended approach is illustrated in Figure 
3-34. Two sets of diagnostic casts are accurately 
mounted so they can be precisely interchanged on 
the articulator. One set is prepared and waxed to the 
intended end point of treatment, with denture teeth 



I 



Section 1 Planning and Preparation 



Record 
base 




Diagnostic 
casts 



Articulator 



<3? 




face bow 



Centric relation 
record and 
facebow 



wr\ 




Original 
cast 



"O 



3 




Simplifying complex prosth- 
odontic treatments by treat- 
ing one arch at a time. 
Working toward a diag- 
nostica Uy waxed end point 




Diagnoslicaliy 
W3xe6 cast 



I IMI V 



Prepared maxillary 
afch 

uu 



iRestored 
jmandibular arcti 




CRR and 
facebow 




Fig. 3-34. Complex prosthodontic treatment sequence using cross-mounted 

diagnostic cases. A, Diagnostic impressions, facebow, and centric relation records 

are made for a patient requiring complex prosthodontic treatment. In this 

schematic, a record base was needed for mounting the mandibular cast. B, The 

diagnostic casts are duplicated, and each set is mounted in the identical orientation 

of an articulator using the facebow and centric record. C, One pair of diagnostic 

casts is waxed to the proposed end point of treatment. If a removable prosthesis is 

planned, denture teeth are set for this step. The other pair of casts is left unaltered. 

D, One arch is treated at a time. For this patient, the mandibular arch has been 

prepared for crowns. The working cast is mounted on the articulator with a centric record made against the (unaltered) 

maxillary teeth. This record is used to mount the working cast against the (unaltered) maxillary cast. Then the maxillary cast 

is removed and replaced with the cross-mounted diagnostically waxed cast. The mandibular restorations are fabricated 

against this cast to ensure an optimal occlusal plane. E, Once the mandibular arch has been restored, the maxillary teeth are 

prepared and mounted against a cast of the newly restored mandibular arch. F, The completed restoration conforms to the 

diagnostic waxing. 




Chapter 3 Treatment Planning 



I 



inserted where removable prostheses are to be used. 
The waxing is carefully evaluated on the articulator 
in relation to occlusion and appearance. When ante- 
rior teeth are to be replaced, they can be assessed for 
appearance and phonetics directly in the mouth if 
they are mounted on a removable record base. De- 
finitive tooth preparation starts in one arch only, 
preserving the occlusal surfaces of the opposing 
arch to act as an essential reference for mounting the 
working cast. The definitive restorations are waxed 
against the diagnostically waxed cast, establishing 
optimal occlusion. When one arch has been com- 
pleted, the opposing cast can be restored, achieving 
the predicted result. 

FOLLOW-UP 

A specific program of follow-up care and regular re- 
call is an essential part of the treatment plan. The 
aim is to monitor dental health, identify the signs of 
disease early, and initiate prompt corrective mea- 
sures as necessary (see Chapter 32). Restorations do 
not last forever, are subject to wear, and may need 
replacement. Adequate follow-up will help main- 
tain long-term health. 

^SUMMARY 

The basis of logical treatment planning consists of 
identifying the patient's needs, eliciting his or her 
expectations and wishes, and comparing these with 
the available corrective materials and techniques. It 
also involves evaluating whether a technique has a 
good prognosis. Then a rational sequence of treat- 
ment may be initiated for symptomatic relief, stabi- 
lization, definitive therapy, and follow-up care. The 
extent of treatment is modified throughout and is 



dictated by the patient's attitude and by the objec- 
tives for that patient. 



OWSSAI^Lj 




abfraction: n (1991) the pathologic loss of hard tooth 
substance caused by biomechanical loading forces. 
Such loss is thought to be due to flexure and ulti- 
mate fatigue of enamel and/or dentin at some loca- 
tion distant from the actual point of loading. 

abutment: n (1634) 1: that part of a structure that di- 
rectly receives thrust or pressure; an anchorage. 2: a 
tooth, a portion of a tooth, or that portion of a dental 
implant that supports and/or retains a prosthesis. 

Ante's Law: [Irvin H. Ante, Toronto, Ontario Canada, 
dentist]: an eponym in fixed partial prosthodontics 
for the observation that the combined pericemental 
area of all abutment teeth supporting a fixed partial 
denture should be equal to or greater in pericemen- 
tal area than the tooth or teeth to be replaced; as for- 
mulated for removable partial prosthodontics, the 
combined pericemental area of the abutment teeth 
plus the mucosa area of the denture base should be 
equal to or greater than the pericemental area of the 
missing teeth (From Ante IH: The fundamental 
principles, design, and construction of crown and 
bridge prosthesis. Dent Item Int 50:215-232, 1928.) 

artificial crown: a metal, plastic, or ceramic restoration 
that covers three or more axial surfaces and the oc- 
clusal surface or incisal edge of a tooth. 

buccolingual relationship: any position of reference rel- 
ative to the tongue and cheeks. 

cantilever: n (1667) a projecting beam or member sup- 
ported on one end. 



Si^dy Qfic^iiam 



1. Discuss 1 2 considerahons that aFfect the design of a fixed partial denture and their generaf impact on FPD 
design. 

2. Discuss at least four different indications For a removable partial denture as opposed \o a fixed parKal 
denture. 

3. When would a nonrigid connector be indicated in a fixed parMol denture? When would W be contraindi- 
cated? 

4. If a patient has a multitude of needs involving all clinical disciplines, in what typical sequence would treat- 
ment be conducted? Why? How are the various stages of occlusal therapy sequenced? Why? 

5. Contrast the replacement of ail \\\e maxillary incisors by an FPD with the replacement of all the mandibu- 
lar incisors by an FPD. htow would you treat each situalion? 

6. Which occlusal forces are of least concern? Why? Which forces/loading should be avoided? Why? 

7. hlow do span length and FPD design influence flexure? Wfien is rigidity essential? Why? 

8. List the steps in treating a pa Kent with extensive restorotive needs using the cross-mounted cast method of 
treating complex prosthodontic patients. Explain briefly the importance of treatment sequence, 




Section 1 Planning and Preparation 



cantilever fixed partial denture: a fixed partial denture 
in which the pontic is cantilevered, (i.e., retained 
and supported only on one end by one or more 
abutments). 

clinical crown: the portion of a tooth that extends from 
the occlusal table or incisal edge to the free gingival 
margin. 

complete crown: a restoration that covers all the coro- 
nal tooth surfaces (mesial, distal, facial, hngual, and 
occlusal). 

complete denture: a removable dental prosthesis that 
replaces the entire dentition and associated struc- 
tures of the maxillae or mandible. 

connector: n in fixed prosthodontics, the portion of a 
fixed partial denture that unites the retainer(s) and 
pontics. 

1 crown: n (12c) 1: the highest part, as the topmost part 

of the skull, head or tooth; the summit; that portion 
of a tooth occlusal to the dentinoenamel junction or 
an artificial substitute for this. 2: an artificial replace- 
ment that restores missing tooth structure by sur- 
rounding part or all of the remaining structure with 
a material such as cast metal, porcelain, or a combi- 
nation of materials such as metal and porcelain. 

2 crown: vt (12c) to place on the head, as to place a 

crown on a tooth, dental implant, or tooth substi- 
tute-usage: implies fabrication of a restoration for 
a tooth on a natural tooth or dental implant. 

crown fracture: micro- or macroscopic cleavage in the 
coronal portion of a tooth. 

crown-root ratio: the physical relationship between 
the portion of the tooth within alveolar bone com- 
pared with the portion not within the alveolar bone, 
as determined by radiograph. 

demineralization: n (ca. 1903) 1: loss of minerals (as 
salts of calcium) from the body. 2: in dentistry, 
decalcification. 

extracoronal retainer: that part of a fixed partial den- 
ture uniting the abutment to the other elements of a 
fixed partial denture that surrounds all or part of 
the prepared crown. 

fixed partial denture: a partial denture that is luted or 
otherwise securely retained to natural teeth, tooth 
roots, and/or dental implant abutments that furnish 
the primary support for the prosthesis-usage: with 
respect to a fixed partial denture retained on dental 
implants, adjectives may be used to describe the 

means of attachment, such as screw retained f p. d., ce- 
ment retained fp.d-also CdAl^dfixed prosthesis. 

fixed partial denture retainer: the part of a fixed partial 
denture that unites the abutment(s) to the remain- 
der of the restoration. 

frenulum: n pi -la (1706) a connecting fold of mem- 
brane serving to support or retain a part. 

high lip line: the greatest height to which the inferior 
border of the upper lip is capable of being raised by 
muscle function. 



horizontal overlap: the projection of teeth beyond 
their antagonists in the horizontal plane. 

hydroxyapatite ceramic: a composition of calcium 
and phosphate in physiologic ratios to provide a 
dense, nonresorbable, and biocompatible ceramic 
used for dental implants and residual ridge 
augmentation. 

i mmediate denture: a complete denture or removable 
partial denture fabricated for placement immedi- 
ately following the removal of natural teeth. 

incisal guidance: 1: the influence of the contacting sur- 
faces of the mandibular and maxillary anterior teeth 
on mandibular movements. 2: the influence of the 
contacting surfaces of the guide pin and guide table 
on articulator movements. 

I ndirect retainer: the component of a removable partial 
denture that assists the direct retainer(s) in prevent- 
ing displacement of the distal extension denture 
base by functioning through lever action on the op- 
posite side of the fulcrum line when the denture 
base moves away from the tissues in pure rotation 
around the fulcrum line. 

indirect retention: the effect achieved by one or more 
indirect retainers of a removable partial denture 
that reduces the tendency for a denture base to 
move in an occlusal direction or rotate about the ful- 
crum Hne. 

intermediate abutment: a natural tooth located be- 
tween terminal abutments that supports a fixed or 
removable prosthesis. 

interim denture: see interim prosthesis. 

i nterim prosthesis : a fixed or removable prosthesis, de- 
signed to enhance esthetics, stabilization, and/or 
function for a limited period of time, after which it 
is to be replaced by a definitive prosthesis. Often 
such prostheses are used to assist in determination 
of the therapeutic effectiveness of a specific treat- 
ment plan or the form and function of the planned 
definitive prosthesis-synonym: provisional prosthe- 
sis, provisional restoration, 

interproximal contact: the area of a tooth that is in 
close association, connection, or touch with an adja- 
cent tooth in the same arch. 

key way: n an interlock using a matrix and patrix be- 
tween the units of a fixed partial denture. It may serve 
two functions: 1) to hold the pontic in the proper re- 
lationship to the edentulous ridge and the opposing 
teeth during occlusal adjustment on the working cast 
(during application of any veneering material) and 2) 
to reinforce the connector after soldering. 

iow lip line: 1 : the lowest position of the inferior bor- 
der of the upper lip when it is at rest. 2: the lowest 
position of the superior border of the lower lip dur- 
ing smiling or voluntary retraction. 

masticatory force: the force applied by the muscles of 
mastication during chewing. 

mesial drift: movement of teeth toward the midline. 



ChapteT a Treatment Planning 



I 



nonrigid connector: any connector that permits limited 
movement between otherwise independent mem- 
bers of a fixed partial denture. 

occlusal analysis: an examination of the occlusion in 
which the interocclusal relations of mounted casts 
are evaluated. 

occlusal device: any removable artificial occlusal sur- 
face used far diagnosis or therapy affecting the re- 
lationship of the mandible to the maxillae. It may be 
used for occlusal stabilization, for treatment of tem- 
poromandibular disorders, or to prevent wear of 
the dentition. 

occlusal equilibration: the modification of the occlusal 
form of the teeth with the intent of equalizing oc- 
clusal stress, producing simultaneous occlusal con- 
tacts, or harmonizing cuspal relations. 

occlusal stability: the equaUzation of contacts that pre- 
vents tooth movement after closure. 

patrix: n pi patrices: 1: a pattern or die used in type 
founding to form a matrix. 2: the extension of a den- 
tal attachment system that fits into the matrix. 

PFM: acronym for porcelain fused to metal. 

plunger cusp: a cusp that tends to force food inter- 
proximally. 

residual bone: that component of maxillary or man- 
dibular bone, once used to support the roots of the 
teeth, that remain after the teeth are lost. 

residual ridge: the portion of the residual bone and its 
soft tissue covering that remains after the removal 
of teeth. 

span length: the length of a beam between two 
supports. 

splinting: v 1: in dentistry, the joining of two or more 
teeth into a rigid unit by means of fixed or re- 
movable restorations or devices. 2: in physiology, 
prolonged muscle spasms that inhibit or prevent 
movement. 

stress breaker: see stress director. 

stress director: a device or system that reheves specific 
dental structures of part or all of the occlusal forces 
and redirects those forces to other bearing struc- 
tures or regions. 

supraeruption: n movement of a tooth or teeth above 
the normal occlusal plane. 

supraocclusion: n malocclusion in which the occluding 
surfaces of teeth extend beyond the normal occlusal 

plane-also called overemption. 

sympathetic nervous system: the part of the autonomic 
nervous system that responds to dangerous or 
threatening situations by preparing a person physi- 
ologically for "fight or flight." 

tooth supported: a term used to describe a prosthesis 
or part of a prosthesis that depends entirely on nat- 
ural teeth for support. 

transitional prosthesis: see interim prosthesis. 

up-right adj the movement of a tooth into an erect or 
normal position. 



working articulation the occlusal contacts of teeth on 
the side toward which the mandible is moved. 

1. Palomo F, Peden J: Periodontal considerations of 
restorative procedures, J Prosthet Dent 36:387, 1976. 

2. Jones RM et al: A comparison of the physical 
properties of four prosthetic veneering materi- 
als, J Prosthet Dent 61:38, 1989. 

3. Vojvodic D et al: The bond strength of polymers 
and metal surfaces using the 'silicoater' tech- 
nique, J Oral Rehabil 22:493, 1995. 

4. Rothfuss LG et al: Resin to metal bond strengths 
using two commercial systems, J Prosthet Dent 
79:270, 1998. 

5. Karmaker AC et al: Continuous fiber reinforced 
composite materials as alternatives for metal al- 
loys used for dental appliances, J BiomaterAppl 
11:318,1997. 

6. Rosenthal L et al: A new system for posterior 
restorations: a combination of ceramic optimized 
polymer and fiber-reinforced composite, Pract 

Periodont Aesthet Dent 9(suppl 5):6, 1997. 

7. Zanghellini G: Fiber-reinforced framework and 
Ceromer restorations: a technical review. Signa- 
ture 4(l):l, 1997. 

8. Claus H: Vita In-Ceram, a new procedure for 
preparation of oxide-ceramic crown and bridge 
framework, Quintessenz Zahntech 16:35, 1990. 

9. Magne P, Belser U: Esthetic improvements and 
in vitro testing of In-Ceram Alumina and Spinell 
ceramic, int ] Prosthodont 10:459, 1997. 

10. Denry IL: Recent advances in ceramics for den- 
tistry, CritRev Oral Biol Med 7:134, 1996. 

11. Sorensen JA et al: IPS Empress crown system: 
three-year clinical trial results, J Calif Dent Assoc 
26:130,1998. 

12. Denry IL et al: Effect of cubic leucite stabiHza- 
tion on the flexural strength of feldspathic den- 
tal porcelain, J Denr i?^^ 75:1928, 1996. 

13. Adell R et al: A 15-year study of osseointegrated 
implants in the treatment of the edentulous jaw, 

Int:S Oral Surg 10:387,1981. 

14. Saunders TR et al: The maxillary complete den- 
ture opposing the mandibular bilateral distal- 
extension partial denture: treatment considera 
tions, J Prosthet Dent 41:124, 1979. 

15. Brewer AA, Morrow RM: Overdentures, ed 2, St 
Louis, 1980, Mosby. 

16. Cheung GS et al: A cHnical evaluation of conven- 
tional bridgework, J Oral Rehabil 17:131, 1990. 

17. Glickman I et al: Photoelastic analysis of internal 
stresses in the periodontium created by occlusal 
forces, J Periodontol 41:30, 1970. 

18. Wright KWJ, Yettram AL: Reactive force distri- 
butions for teeth when loaded singly and when 



I 



Sprtion 1 Planning and Preparation 



used as fixed partial denture abutments, J Pros- 
thet Dent 42:411, 1979. 

19. Yang HS et al: Stress analysis of a cantilevered 
fixed partial denture with normal and reduced 
bone support, J Pro sthet Dent 76:424, 1996. 

20. Briggs P et al: The single unit, single retainer, 
cantilever resin-bonded bridge, Br Dent J 
181:373, 1996. 

21. Christensen GJ: When to use fillers, build-ups 
or posts and cores, J Am Dent Assoc 127:1397, 
1996. 

22. Miller TE: Orthodontic therapy for the restora- 
tive patient. I. The biomechanic aspects, J Pros- 
thet Dent 6l:26d>, 19^9. 

23. Holmgren K et al: The effects of an occlusal 
splint on the electromyographic activities of the 
temporal and masseter muscles during maximal 
clenching in patients with a habit of nocturnal 
bruxism and signs and symptoms of cran- 
iomandibular disorders, J OralRehabil 17:447, 
1990. 

24. Ante IH: The fundamental principles of abut- 
ments, Mich State Dent Soc Bull 8: 14, My 1926. 

25. Dykema RW et al: Johnston 's modem practice in 
fixed pro sthodontics, ed 4, Philadelphia, 1986, WB 

Saunders, p 4. 

26. Tylman SD, Malone WFP: Tylman's theory and 
practice affixed prosthodontics, ed 7, St Louis, 

1978, Mosby, p 15. 

27. Shillingburg HT et al: Fundamentals offixed 

pro sthodontics, ed 2, Chicago, 1981, Quintessence 
PubHshing, p 20. 



28. Jepsen A: Root surface measurement and a 
method for x-ray determination of root surface 
area, A cm Odontol Scand 21:35, 1963. 

29. Nyman S, Ericsson I: The capacity of reduced 
periodontal tissues to support fixed bridgework, 

J Clin Periodontol 9:409, 1982. 

30. Freilich MA et al: Fixed partial dentures sup- 
ported by periodontally compromised teeth, 

J Prosthet Dent 65:607, 1991. 

31. Decock V et al: 18-year longitudinal study of 
cantilevered fixed restorations, inter J Prosthodont 
9:331, 1996. 

32. Penny RE, Kraal JH: Crown-to-root ratio: its sig- 
nificance in restorative dentistry, J Prosthet Dent 
42:34, 1979. 

33. Nyman S et al: The role of occlusion for the sta- 
bility of fixed bridges in patients with reduced 

periodontal tissue support, J Clin Periodontol 

2:53, 1975. 

34. Laurell L et al: Long-term prognosis of extensive 
polyunit cantilevered fixed partial dentures, 

J Prosthet Dent 66:545, 1991. 

35. Smyd ES: Dental engineering, J Dent Res 27:649, 
1948. 

36. Dykema RW: Fixed partial prosthodontics, 

JTenn Dent Assoc 42:309, 1962. 

37. Olin PS et al: Improved pontic/tissue relation- 
ships using porous coralline hydroxyapatite 
block, J Prosthet Dent 66:234, 1991. 



Principles of Occlusion 



anterior guidance 

articular disl< 

attrition 

Bennett movement 

border movement 

bruxism 

capsule 

clenching 

determinants of occlusion 

disocclusion 

eccentric 

excursion 

group function 

guidance 

horizontal overlap 

i ntercondylar distance 



interference 
malocclusion 
mandibular movement 
mandibular sideshift 
mutual protection 
nonworking side 
occlusal device 
parafunction 
pathogenic occlusion 
Posselt 

speaking space 
temporomandibular joint 
terminal hinge axis 
translation 
vertical overlap 
working side 



Most restorative procedures affect the shape of the 
occlusal surfaces. Proper dental care ensures that 
functional contact relationships are restored in har- 
mony with both dynamic and static conditions. 
Maxillary and mandibular teeth should contact to 
allow optimum function, minimal trauma to the 
supporting structures, and an even load distribu- 
tion throughout the dentition. Positional stability of 
the teeth is critical if arch integrity and proper func- 
tion are to be maintained over time. 

As an aid to the diagnosis of occlusal dysfunc- 
tion, it is helpful to evaluate the condition of specific 
anatomic features and functional aspects of a pa- 
tient's occlusion with reference to a concept of "op- 
timum" or "ideal" occlusion. Deviation from this 
concept can then be measured objectively and may 
prove to be a useful guide during treatment plan- 
ning and active treatment phases. 

Over time, many concepts of "ideal" occlusion 
have been proposed. In the literature, the concept of 
what is "ideal," "acceptable," and "harmful" con- 
tinues to evolve. 

This chapter reviews the anatomic structures im- 
portant to the study of occlusion and includes a dis- 
cussion of mandibular movement. The concepts of 
ideal versus pathologic occlusion are introduced, as 



is the history of occlusal theory. The chapter con- 
cludes with guidelines for the initial phase of oc- 
clusal treatment. 



ANATOMY 

TEMPOROMANDIBULAR JOINTS 

The major components of the temporomandibular 
joints are the cranial base, the mandible, and the 
muscles of mastication with their innervation and 
vascular supply. Each joint can be described as gin- 
glymoarthrodial, meaning that it is capable of both 
a hinging and a gliding articulation. An articular 
disk separates the mandibular fossa and articular 
tubercle of the temporal bone from the condylar 
process of the mandible. 

The articulating surfaces of the condylar pro- 
cesses and fossae are covered with avascular fibrous 
tissue (in contrast to most other joints, which have 
hyaline cartilage). The articular disk consists of 
dense connective tissue; it also is avascular and de- 
void of nerves in the area where articulation nor- 
mally occurs. Posteriorly it is attached to loose vas- 
cularized connective tissue, the retrodiscal pad or 
bilaminar zone*, which connects to the posterior 
wall of the articular capsule surrounding the joint 
(Fig. 4-1). Medially and laterally the disk is attached 
firmly to the poles of the condylar process. Anteri- 
orly it fuses with the capsule and with the superior 
lateral pterygoid muscle. Superior and inferior to 
the articular disk are two spaces, the superior and 
inferior synovial cavities. These are bordered pe- 
ripherally by the capsule and the synovial mem- 
branes and are filled with synovial fluid. Because of 
its firm attachment to the poles of each condylar 
process, the disk follows condylar movement dur- 
ing both hinging and translation, which is made 
possible by the loose attachment of the posterior 
connective tissues. 



^Called Mam/naA" because it consists of two layers: an 
elastic superior layer and a collagenous inelastic infe- 
rior layer. 



83 



I 



Section 1 Planning and Preparation 



SLfperfor [aieral 
pterygoid muscle 




Inferior lateral 
pterygoid musde 



Mandibular fossa 
■^^^ Articular disc 

RetrodiscaltissLfe 
Superior joint 
cavity 

Condylar procesi 

Inferior [oint 
cavity 

Capsular ligament 



Fig. 4- 1 . Temporomandibular joint (lateral section). The mandible is open. 

(A courtesy Dr. K.A. Laurell.) 



Mdiulibuidr Ligaments 



TAB IE 4"L 



Temporomandibular 
Superficial 

Medial 

Sphenomandibular 

Styl Oman dibu lor 



Origin 



Outer surface oF 
articular eminence 

Crest of articular 
eminence 

Spine of sphenoid 

Styloid process 



Insertion 



Posterior aspect of neck 
of condylar process 

Lateral aspect oF neck 
of condylar process 

Inferior to lingula 

Mandibular angle and 
fascia of medial 
pterygoid muscle 



Function 



Limits mandibular rotation on opening 
Limits posterior movement 

Accessory to temporomandibular articulations- 
influence on mandibular nnovement disputed 

Limits extreme protrusion of tfie mandible; 
influence on mandibular movement disputed 



LIGAMENTS 

The body of the mandible is attached to the base of 
the skull by muscles and also by three paired liga- 
ments (Table 4-1): the temporomandibular (also 
called the lateral), the sphenomandibular, and the 
stylomandibular. Ligaments cannot be stretched sig- 
nificantly, so they limit the movement of joints. The 
temporomandibular ligaments limit the amount of 
rotation of the mandible and protect the structures of 
the joint, limiting border movements.' The spheno- 



mandibular and stylomandibular ligaments (Fig. 
4-2) limit separation between the condylar process 
and the disk; the stylomandibular ligaments also 
limit protrusive movement of the mandible. 

MUSCULATURE 

Several muscles are responsible for mandibular 
movements. These can be grouped into the muscles 
of mastication and the suprahyoid muscles (Fig. 
4-3). The former include the temporal, the masseter. 



Chapter 4 Principles of Occlusion 



I 




Joint capsule 

Sphenomandibular 
ligament 



Stylomandibular 
ligament 




L,igaments cannot be 
stretched, which limits 
movement. 



Jofnt capsule 



Temporomandibular 
ligament 




Stylomandibular 
ligament 



Fig. 4-2. Ligaments of the temporomandibular joint. A, Mesial view. B, Lateral view. 



Lateral pterygoid 
muscle 



Medial pterygoid 
muscle 




Temporal 
muscle 



Masseter 
muscle 




Mylohyoid 
muscle 

Stylohyoid 
muscle 

Posterior belly of 
digastric muscle 



/ ! \Ant 



Hyoglossal 
muscle 



Anterior Iwlly of 
digastric muscle 



Hyoid bone 



Fig. 4-3. The muscles of mastication and the suprahyoids. 



and the medial and lateral pterygoids; the latter are 
the geniohyoid, the mylohyoid, and the digastrics. 
Their respective origins, insertions, and innervation 
and vascular supply are summarized in Table 4-2. 



Muscular Function. The functions of the man- 
dibular muscles are well-coordinated, complex events. 

The three paired muscles of mastication provide 
elevation and lateral movement of the mandible. 



Section 1 Planning and Preparation 



Temporal 



Origin 



Lateral surface of 
skull 



Mossefer 



Medial pterygoid 



Superior lateral 
pterygoid 



Inferior lateral 
pterygoid 

Mylohyoid 



Geniohyoid 

Anterior belly 
of digastrtc 



Zygomatic arch 



Pterygoid fossa 
and med?al 
surface of lat- 
eral pterygoid 
plate 

infratemporal 
surface of 
greater wing 
of sphenoid 

Lateral surface of 
iaterol ptery- 
goid plate 

Inner surface of 
mandible 

Genial tubercle 

Tendon linked 
to hyoid by 



InserHoti 



Coronoid 
process and 
anterior bor- 
der of ramus 



Angle of 
mandible 



Medial surface 
of angle of 



Inner\'ation Vasctilar Supply 



Temporal nerve 
[branch of 



man 



dible 



Articular cap- 
sule and disc, 
neck of 
condyfe 

Neck of condyle 



Hyoid and my- 
lohyoid 
raphe 

Hyoid 

Digastric fossa 
(lower border 
of mandible) 



ma 



ndfbulc 



Masseteric nerve 
(division of 
trigeminal) 

Medial pterygoid 
nerve (division of 
trigeminal) 



Branch of masseteric 
or buccal nerve 

Branch of masseteric 
or buccal nerve 

Branches of mylohy- 
oid nerve (division 
of trigeminal) 

First cervical via hy- 
poglossal nerve 

Branch of mylohyoid 
nerve (division of 
trigeminal) 



Middle and 
deep tempo- 
ral arteries 
(branches of 
superficiol 
temporal and 
maxillary) 

Masseteric 
artery (branch 
of maxillary) 

Branch of maxil- 
lary artery 



Branch of maxil- 
lary artery 

Branch of maxil- 
lary artery 

Submental 
artery 

Branch of lin- 
gual artery 

Bronch of facial 
artery 



Function 



Elevates and retracts 
javi^, assists in rota- 
tion, active in 
clenching 



Elevates and protracts 
jaw, assists in lot- 
erot movement, ac- 
tive in clenching 

Elevates jaw, causes 
lateral movement 
and protrusion 



Positions disc in 
closing 

Protrudes and de- 
presses jaw, causes 
lateral movement 

Elevates and stabi- 
lizes hyoid 

Elevates and draws 
hyoid forward 

Elevates hyoid, de- 
presses jaw 



These are the temporals, the masseters, and the me- 
dial pterygoids. The lateral pterygoid muscles, 
each with two bellies (which some suggest should 
be considered as two separate muscles), function 
horizontally during opening and closing; the infe- 
rior belly (or inferior lateral pterygoid) is active 
during protrusion, depression, and lateral move- 
ment; the superior belly (or superior lateral ptery- 
goid) is active during closure. The last is thought 
to assist in maintaining the integrity of the 
condyle-disk assembly by pulling the condylar 
process firmly against the disk, because the supe- 
rior belly has been shown to attach to the disk and 
the neck of the condyle. 

The muscles of the suprahyoid group have a dual 
function. They can elevate the hyoid bone or de- 
press the mandible. The movement that results 
when they contract depends on the state of contrac- 
tion of the other muscles of the neck and jaw region. 
When the muscles of mastication are in a state of 



contraction, the suprahyoids will elevate the hyoid 
bone. However, if the infrahyoid muscles (which 
anchor the hyoid bone to the sternum and clavicle) 
are contracted, the suprahyoids will depress and re- 
tract the mandible. The geniohyoid and mylohyoid 
initiate the opening movements, and the anterior 
belly of the digastric completes mandibular depres- 
sion. Although the stylohyoid muscle (which also 
belongs to the suprahyoid group) may contribute 
indirectly to mandibular movement through fixa- 
tion of the hyoid bone, it does not play a significant 
role in mandibular movement. 

Dentition 

The relative positions of the maxillary and mandib- 
ular teeth influence mandibular movement. Many 
"ideal" occlusions have been described . 2 In most of 
these, the maxillary and mandibular teeth contact 
simultaneously when the condylar processes are 
fully seated in the mandibular fossae and the teeth 



Chapter 4 Principles of Occlusion 



I 




The Angle Class 1 occlusal relationship. 



do not interfere with harmonious movement of 
the mandible during function. In the fully bilateral 
seated position of the condyle-disk assemblies, 
the maxillary and mandibular teeth ideally exhibit 
maximum intercuspation. This means that the 
maxillary lingual and mandibular buccal cusps of 
the posterior teeth are in evenly distributed and 
stable contact with the opposing occlusal fossae. 
These centric cusps can then act as stops for verti- 
cal closure without excessively loading any one 
tooth. 

If the mesiobuccal cusp of the maxillary first 
molar is aligned with the buccal groove of the 
mandibular first molar, an Angle Class I ortho- 
dontic relationship (Fig. 4-4) exists; this is consid- 
ered normal (see glossary). In such a relationship, 
the anterior teeth overlap both horizontally and 
vertically. Orthodontic textbooks 3 have tradition- 
ally described an arbitrary 2 mm for horizontal 
and vertical overlap as being ideal. For most pa- 
tients, however, greater vertical overlap of the an- 
terior teeth is desirable to prevent undesirable 
posterior tooth contact as a result of flexing of the 
mandible during mastication. Empirically, denti- 
tions with greater vertical overlap of the anterior 
teeth appear to have a better long-term prognosis 
in comparison to dentitions with minimal vertical 
overlap. 

CENTRIC RELATION 

Centric relation is considered the optimal mandibu- 
lar position in which the bilateral condyle-disk as- 
semblies are fully seated in their corresponding 
glenoid fossae, with the condyles positioned along 
the anterior slope of the articular eminence. Centric 
relation is considered a reliable and reproducible ref- 
erence position. If the intercuspal position coincides 
with the centric relation position, restorative treat- 
ment is often straightforward. When the intercuspal 
position does not coincide with centric relation, it is 
necessary to determine whether corrective occlusal 
therapy is needed before restorative treatment. 




Rotation 



Fig . 4-5 . Three-dimensional movement of a body can be 
defined by a combination of translation (all points within 
the body having identical movement) and rotation (all 
points turning around an axis). 



Frontal 



Sagittal 
Hori/onral 




MANDIBULAR 



Reference planes. 



MOVEMENT 



As for any other movement in space, complex 
three-dimensional mandibular movement can be 
broken down into two basic components: transla- 
tion, when all points within a body have identical 
motion, and rotation, when the body is turning 
about an axis (Fig. 4-5). Every possible three-dimen- 
sional movement can be described in terms of these 
two components. In addition, it is easier to under- 
stand mandibular movement when the components 
are described as projections in three perpendicular 
planes: sagittal, horizontal, and frontal (Fig. 4-6). 



REFERENCE PLANES 



Sagittal Plane (Fig. 4-7). In the sagittal plane, the 
mandible is capable of a purely rotational move- 
ment as well as translation. Rotation occurs around 
the terminal hinge axis, an imaginary horizontal 
line through the rotational centers of the left and 
right condylar processes. The rotational movement 
is limited to about 12 mm of incisor separation 
before the temporomandibular ligaments and 




Section 1 Planning and Preparation 




Border movements 
comprise pure ro- 
tation and translatory 
movement. 




Fig. 4-7. A, Rotation of the mandible in a sagittal plane can be made around the terminal hinge axis. 
B, After about 12 mm of incisal opening, the mandible is forced to translate. C, Maximum opening; the 
condyles have translated forward. 



structures anterior to the mastoid process force the 
mandible to translate. The initial rotation or hinging 
motion is between the condyle and the articular 
disk. During translation, the lateral pterygoid mus- 
cle contracts and moves the condyle-disk assembly 
forward along the posterior incline of the tubercle. 
Condylar movement is similar during protrusive 
mandibular movement. 

Horizontal Plane. In the horizontal plane, the 
mandible is capable of rotation around several ver- 
tical axes. For example, lateral movement consists 
of rotation around an axis situated in the working 
(laterotrusive) condylar process (Fig. 4-8) with 
relatively little concurrent translation. A slight 
lateral translation-known as Bennett movementt4 
mandibular sideshift, or laterotmsion (Fig. 4-9)-is 
frequently present. This may be slightly forward or 
slightly backward (lateroprotrusion or lateroretru- 
sion). The orbiting (nonworking) condyle travels 
forward and medially as limited by the medial as- 
pect of the mandibular fossa and the temporo- 
mandibular ligament. Finally, the mandible can 
make a straight protrusive movement (Fig. 4-10). 

Frontal Plane. When observing a lateral move- 
ment in the frontal plane, the mediotrusive (or non- 
working) condyle moves down and medially while 
the laterotrusive (or working) condyle rotates 
around the sagittal axis perpendicular to this plane 
(Fig. 4-11). Again, as determined by the anatomy of 
the medial wall of the mandibular fossa on the 
mediotrusive side, transtrusion may be observed: as 
determined by the anatomy of the mandibular fossa 
on the laterotrusive side, this may be lateral and up- 
ward or lateral and downward (laterosurtrusion 
and laterodetrusion). A straight protrusive move- 
ment observed in the frontal plane, with both 
condylar processes moving downward as they 




Fig. 4-8. Rotation in the horizontal plane occurs during 
lateral movement of the mandible. (The vertical axis is situ- 
ated in the condylar process.) Normally there is relatively 
little translation (sideshift). 



slide along the tubercular eminences, is shown in 
Figure 4-12. 

BORDER MOVEMENTS 

Mandibular movements are limited by the tem- 
poromandibular joints and ligaments, the neuro- 
muscular system, and the teeth. Posselt was the 
first to describe the extremes of mandibular move- 
ment, which he called border movements (Fig. 4-13). 
His classic work is well worth reviewing as one at- 
tempts to understand how the determinants control 
the extent to which movement can occur. 

Posselt used a three-dimensional representation 
of the extreme movements the mandible is capable 
of (Fig. 4-13, B). All possible mandibular move- 
ments occur within its boundaries. At the top of 
both illustrations, a horizontal tracing represents 
the protrusive movement of the incisal edge of the 
mandibular incisors. 

Starting at the intercuspal positions in the protru- 
sive pathway, the lower incisors are initially guided 



Chapter 4 Prindplps of Orrliision 



I 





Fig. 4-9. Right lateral mandibular movement in the hori- 
zontal plane. 



Fig. 4-1 1 . Lateral movement in the frontal plane. 





Fig. 4-10. Protrusive mandibular movement in the hori- 
zontal plane. 



Fig. 4-1 2. Protrusive movement in the frontal plane. 





Fig. 4-1 3. A, Mandibular border movement in the sagittal plane. B, Posselt's three-dimensional repre- 
sentation of the total envelope of mandibular movement. 1, Mandibular incisors track along the lingual 
concavity of the maxillary anterior teeth. 2, Edge-to-edge position. 3, Incisors move superiorly until pos- 
terior tooth contact recurs. 4, Protrusive path. 5, Most protrusive mandibular position. 



I 



SerCtion 1 Planning and Preparation 




Posterior Determinants 

Indinafion of articular eminence 

Medial wolf of glenoid fossa 
Intercondylar distance 



Anterior Determinants 
Horizontal overlap of anterior feetfi 

Verffcal overlap of anterior ^eetfi 



Other 

Occlusal plane 

Curve of Spee 



Variation 

Steeper 

Flatter 

Afbws more lateral translotion 

Allows minimal lateral tran&btlon 

Greater 

Lesser 



Increased 
Reduced 
Increased 
Reduced 



More parallel to condylar guidance 
Less poroilel to condylar guidance 
More convex (shorter radiusf 
Less convex (larger radius] 



Impact on RLsroKAnos 
Posterior cusps may be taller 
Posterior cusps must be sfiorter 
Posterior cusps musi be shorter 
Posterior cusps may be taller 
Smaller angle between laterotrusive ond 

mediotrusive movement 
Increased angle between laterotrusive ond 

mediotrusive movement 

Posterior cusps must be shorter 
Posterior cusps may be taller 
Posterior cusps may be toller 
Posterior cusps must be shorter 

Posterior cusps must be shorter 
Posterior cusps may be longer 
The most posterior cusps must be shorter 
The most posterior cusps may be longer 




Fig. 4-14. Posterior determinants of occlusion. A, Angle of tlie articular eminence (condylar guid- 
ance angle). 1, Flat; 2, average; 3, steep. B, Anatomy of the medial walls of the mandibular fossae. 1, 
Greater than average; 2, average; 3, minimal sideshift. 



by the lingual concavity of the maxillary anterior 
teeth. This leads to gradual loss of posterior tooth 
contact as the incisors reach the edge-to-edge posi- 
tion. This is represented in Posselt's diagram by the 
initial downward slope. As the mandible moves far- 
ther protrusively, the incisors slide over a horizontal 
trajectory representing the edge-to-edge position 
(the flat portion in the diagram), after which the 
lower incisors move upward until new posterior 
tooth contact occurs. Further protrusive movement 
of the mandible typically takes place without signif- 
icant tooth contact. 



The border farthest to the right of Posselt's solid 
(see Fig. 4-13, B) represents the most protruded open- 
ing and closing stroke. The maximal open position of 
the mandible is represented by the lowest point in 
the diagram. The left border of the diagram repre- 
sents the most retruded closing stroke. This move- 
ment occurs in two phases: The lower portion con- 
sists of a combined rotation and translation, until the 
condylar processes return to the fossae. The second 
portion of the most retruded closing stroke is repre- 
sented by the top portion of the border that is farthest 
to the left in Posselt's diagram. It is strictly rotational. 



Chapter 4 Principles of O rrlnsinn 



I 




The anterior guidance between 
the maxillary and mandibular 
anterior teeth has a direct in- 
ftuence on the direction of 
mandibular movement. 



Fig. 4-15. Anterior determinants of occlusion. Different incisor relationships with differing horizontal 
and vertical overlaps (HO and VO) produce different anterior guidance angles (AGA). A, Class 1. 
B, Class 11, Division 2 (increased VC; steep AGA). C, Class 11, Division 1 (increased HO; flat AGA). 



Posterior and Anterior Determinants (Table 

4-3). The characteristics of mandibular movement 
are established posteriorly by the morphology of 
the temporomandibular joints and anteriorly by the 
relationship of the anterior teeth. 

The posterior determinants (Fig. 4- 14) -shape of 
the articular eminences, anatomy of the medial 
walls of the mandibular fossae, configuration of the 
mandibular condylar processes-cannot be con- 
trolled, nor is it possible to influence the neuromus- 
cular responses of the patient, unless it is done by 
indirect means (e.g., through changes in the config- 
uration of the contacting teeth or by the provision of 
an occlusal appliance). If a patient has steeply 
sloped eminences, there will be a large downward 
component of condylar movement during lateral 
and protrusive excursions. Similarly, the anatomy 
of the medial wall of each fossa normally will allow 
the condyle to move slightly medially as it travels 
forward (mandibular sideshift, or transtrusion). The 
sideshift will become greater as the extent of medial 
movement increases. However, the anatomy of the 
joint dictates the actual path and timing of condylar 
movement. Movement of the laterotrusive or work- 
ing condylar process is influenced predominantly 
by the anatomy of the lateral wall of the mandibu- 
lar fossa. The amount of the sideshift is, of course, 
a function of the mediotrusive or nonworking 



condyle; on the working side, however, it is the 
anatomy of the lateral aspect of the fossa that guides 
the working condyle straight out or upward and 
downward. The amount of sideshift does not ap- 
pear to increase as the result of a loss of occlusion e 

The anterior determinants (Fig. 4-15) are the verti- 
cal and horizontal overlaps and the maxillary lin- 
gual concavities of the anterior teeth. These can be 
altered by restorative and orthodontic treatment. A 
greater vertical overlap causes the direction of 
mandibular opening to be more vertical during the 
early phase of protrusive movement and creates a 
more vertical pathway at the end of the chewing 
stroke. Increased horizontal overlap allows a more 
horizontal jaw movement. 

Although the posterior and anterior determinants 
combine to affect mandibular movement, no correla- 
tion has been established?; that is, patients with steep 
anterior guidance angles do not necessarily have a 
steep posterior disclusion, and vice versa. 

FUNCTIONAL MOVEMENTS 

Most functional movement of the mandible (as oc- 
curs during mastication and speech) takes place in- 
side the physiologic limits established by the teeth, 
the temperomandibular joints, and the muscles and 
ligaments of mastication; therefore, these move- 
ments are rarely coincident with border movements. 



I 



section 1 Planning and Preparation 



Chewing. When incising food, adults open their 
mouth a comfortable distance and move the 
mandible forward until they incise, with the anterior 
teeth meeting approximately edge to edge. The food 
bolus is then transported to the center of the mouth 
as the mandible returns to its starting position, with 
the incisal edges of the mandibular anterior teeth 
tracking along the lingual concavities of the maxil- 
lary anterior teeth (Fig. 4-16). The mouth then opens 
slightly, the tongue pushes the food onto the occlusal 
table, and after moving sideways, the mandible 
closes into the food until the guiding teeth (typically 
the canines) contact.' The cycle is completed as the 
mandible returns to its starting position. 9 This pat- 
tern repeats itself until the food bolus has been re- 
duced to particles that are small enough to be swal- 
lowed, at which point the process can start over. The 
direction of the mandibular path of closure is influ- 
enced by the inclination of the occlusal plane with 
the teeth apart and by the occlusal guidance as the 
jaw approaches intercuspal position.'" 

The chewing pattern observed in children differs 
from that found in adults. Until about age 10, chil- 
dren begin the chewing stroke with a lateral move- 
ment. After the age of 10, they start to chew increas- 
ingly like adults, with a more vertical stroke" (Fig. 
4-17). Stimuli from the pressoreceptors play an im- 
portant role in the development of functional chew- 
ing cycles. 12 

Mastication is a learned process. At birth no oc- 
clusal plane exists, and only after the first teeth have 
erupted far enough to contact each other is a mes- 
sage sent from the receptors to the cerebral cortex. 



which controls the stimuli to the masticatory mus- 
culature. Stimuli from the tongue and cheeks, and 
perhaps from the musculature itself and from the 
periodontium, may influence this feedback pattern. 

Speaking. The teeth, tongue, lips, floor of the 
mouth, and soft palate form the resonance chamber 
that affects pronunciation. During speech, the teeth 
are generally not in contact, although the anterior 
teeth may come very close together during "C," 
"CH," "S," and "Z" sounds, forming the "speaking 
space."" When pronouncing the fricative "F," the 
inner vermilion border of the lower lip traps air 
against the incisal edges of the maxillary incisors. 
Phonetics is a useful diagnostic guide for correcting 
vertical dimension and tooth position during fixed 
and removable prosthodontic treatment. 14 

PARAFUNCTIONAL MOVEMENTS 

Parafunctional movements of the mandible may be 
described as sustained activities that occur beyond 
the normal functions of mastication, swallowing, and 
speech. There are many forms of parafunctional ac- 
tivities, including bruxism, clenching, nail biting, 
and pencil chewing, among others. Typically, para- 
function is manifested by long periods of increased 
muscle contraction and hyperactivity. Concurrently, 
excessive occlusal pressure and prolonged tooth con- 
tact occur, which is inconsistent with the normal 
chewing cycle. Over a protracted period this can re- 
sult in excessive wear, widening of the periodontal 
Hgament (PDL), and mobility, migration, or fracture 
of the teeth. Muscle dysfunction such as myospasms. 



HORIZONTAL PLANE 



SAGITTAL PLANE 




^--^ 



Bofdef ' 
movement 




^-^^ Border 
movement 



__^__ Border 

movement 

Scale 



[•^10 mm — -^ 



FRONTAL PLANK 



Fig. 4-16. Comparison of border and chewing movements for soft food at the central incisor. Sagittal, 
frontal, and horizontal views in an orthographic projection. 

(Fram Gibbs CH et ai : J Prosthct Dcnt 46) 308, 1 98 1 .) 



Chapter 4 Principles of Occlusion 



I 



myositis, myalgia, and referred pain (headaches) 
from trigger point tenderness may also occur. The de- 
gree of symptoms varies considerably among indi- 
viduals. The two most common forms of parafunc- 
tional activities are bruxism and clenching. Increased 
radiographic bone density is often seen in patients 
with a history of sustained parafunctional activity. 

Bruxism. Sustained grinding, rubbing together, 
or gnashing of the teeth with greater-than-normal 
chewing force is known as bruxism (Fig. 4-18). This 
activity may be diurnal, nocturnal, or both. Al- 
though bruxism is initiated on a subconscious level, 
nocturnal bruxism is potentially more harmful be- 
cause the patient is not aware of it while sleeping. 
Therefore, it can be difficult to detect, but it should 
be suspected in any patient exhibiting abnormal 
tooth wear or pain. The prevalence of bruxism is 
about 10% and is less common with age." The etiol- 
ogy of bruxism is often unclear. Some theories relate 
bruxism to malocclusion, neuromuscular distur- 
bances, responses to emotional distress, or a combi- 
nation of these factors. A study on cohort twins has 
demonstrated substantial genetic effects,'" the con- 
dition has been related to sleep disturbance," and 
the symptoms of bruxism are three times more com- 



mon in smokers. Altered mastication has been ob- 
served in subjects who brux and may be due to 
an attempt to avoid premature occlusal contacts (oc- 
clusal interferences). There may also be a neuro- 
muscular attempt to "rub out" an interfering cusp. 
The fulcrum effect of rubbing on posterior interfer- 
ences will create a protrusive or laterotrusive move- 
ment that can cause overloading of the anterior 
teeth, with resultant excessive anterior wear. It is 
common for wear on anterior teeth to progress from 
initial faceting on the canines to the central and lat- 
eral incisors. Once vertical overlap diminishes as 
the result of wear, posterior wear facets are com- 
monly observed. However, the chewing patterns of 
normal subjects can be quite varied, and the rela- 
tionship, if any, between altered mastication and oc- 
clusal dysfunction is not clear 25 

The causes of bruxism are difficult to determine. 
One theory states that bruxism is performed on a 
subconscious reflex- controlled level and is related 
to emotional responses and occlusal interferences. 
In certain malocclusions, the neuromuscular system 
exerts fine control during chewing to avoid particu- 
lar occlusal interferences. As the degree of muscle 
activity necessary to avoid the interferences be- 
comes greater, an increase in muscle tone may 




-lOmm- 



Age 6 
Chewing cheese 



Age 12 
Right side chewing 



Fig. 4-17. Frontal views of chewing on the left side. The dashed Unes are border movements. 

A, Chewing in a young person, characterized by a wide lateral movement on opening and decreased 

lateral movement on closing. B, In an older child, the chewing pattern resembles that of an adult. 

(From WickwireNA et al: Angle Orthod 51:48, 1981.) 



I 



Section 1 Planning and Preparation 



result, with subsequent pain in the hyperactive mus- 
culature, which in turn can lead to restricted move- 
ment. The relationship, if any, between bruxism and 
temporomandibular disorders is still unclear. 

Patients who brux can exert considerable forces 
on their teeth, and much of this may have a lateral 
component. Posterior teeth do not tolerate lateral 
forces as well as vertical forces in their long axes. 
Buccolingual forces, in particular, appear to cause 
rapid widening of the periodontal ligament space 
and increased mobihty. 

Clenching. Clenching is defined as forceful 
clamping together of the jaws in a static relation- 
ship. The pressure thus created can be maintained 
over a considerable time with short periods of re- 




laxation in between. The etiology can be associated 
with stress, anger, physical exertion, or intense con- 
centration on a given task, rather than an occlusal 
disorder. As opposed to bruxism, clenching does 
not necessarily result in damage to the teeth because 
the concentration of pressure is directed more or 
less through the long axes of the posterior teeth 
without the involvement of detrimental lateral 
forces. Abfractions-cervical defects at the CEJ- 
may result from sustained clenching. 28 Also, the 
increased load may result in damage to the peri- 
odontium, temporomandibular joints, and muscles 
of mastication. Typically, the elevators will become 
overdeveloped. A progression of muscle splinting, 
myospasm, and myositis may occur, causing the pa- 
tient to seek treatment. As with bruxism, clenching 
can be difficult to diagnose and difficult if not im- 
possible for the patient to voluntarily control. 

^] ( STORY OF OCCLUSAL STUDIES 

Historically, the study of occlusion has undergone 
an evolution of concepts. These can be broadly cat- 
egorized as bilaterally balanced 3° unilaterally bal- 
anced, and mutually protected. Current emphasis in 
teaching fixed prosthodontics and restorative den- 
tistry has been on the concept of mutual protection 
(Fig. 4-19). However, since restorative treatment re- 
quirements vary, the clinician should understand 
possible combinations of occlusal schemes and their 
advantages, disadvantages, and indications. 

In most patients, maximum tooth contact occurs 
anterior to the centric relation position of the 
mandible. Often, this maximum intercuspation po- 
sition anterior to centric relation is referred to as cen- 
tric occlusion, although the term is also used to refer 
to occlusal contact in centric relation. To avoid con- 




Fig. 4-18. Extensive abrasion (tooth wear) resulting 
from parafunctional grinding in a 23 -year-old patient. 



Fig. 4-1 9. Canine-guided or mutually protected occlu- 
sion. During lateral excursions, there are no contacts on the 
mediotrusive (non working) side; all contacts are between 
the laterotrusive (working side) canines. 



Chapter 4 Principles nf Orrlnsinn 



I 



fusion, maximum intereuspation (MI) and centric rela- 
tion (CR) are the terms used in this text. 

BILATERALLY BALANCED ARTICULATION 

Early work in removable prosthodontics centered 
around the concept of a bilaterally balanced articu- 
lation. This requires having a maximum number of 
teeth in contact in maximum intereuspation and all 
excursive positions. In complete denture fabrica- 
tion, this tooth arrangement helps maintain denture 
stability because the nonworking contact prevents 
the denture from being dislodged. However, as the 
principles of bilateral balance were applied to the 
natural dentition and in fixed prosthodontics, it 
proved to be extremely difficult to accomplish, even 
with great attention to detail and sophisticated ar- 
ticulators. In addition, high rates of failure resulted. 
An increased rate of occlusal wear, increased or ac- 
celerated periodontal breakdown, and neuromus- 
cular disturbances were commonly observed. The 
last were often relieved when posterior contacts on 
the mediotrusive side were eliminated in an attempt 
to eliminate unfavorable loading. Thus the concept 
of a unilaterally balanced occlusion (group func- 
tion) evolved^i (Fig. 4-20). 

UNILATERALLY BALANCED ARTICULATION 
(GROUP FUNCTION) 

In a unilaterally balanced articulation, excursive 
contact occurs between all opposing posterior teeth 
on the laterotrusive (working) side only. On the 
mediotrusive (nonworking) side, no contact occurs 
until the mandible has reached centric relation. 
Thus, in this occlusal arrangement the load is dis- 
tributed among the periodontal support of all pos- 
terior teeth on the working side. This can be advan- 
tageous if, for instance, the periodontal support of 




Fig. 4-20. Group function or unilaterally balanced occlu- 
sion. During lateral excursions, there are no contacts be- 
tween teeth on the mediotrusive (nonworking) side, but 
even excursive contacts occur on the laterotrusive (work- 
ing) side. 



the canine is compromised. While on the working 
side, occlusal load is distributed during excursive 
movement, and the posterior teeth on the non- 
working side do not contact. In the protrusive 
movement, no posterior tooth contact occurs. 

Long Centric. As the concept of unilateral bal- 
ance evolved, it was suggested that allowing some 
freedom of movement in an anteroposterior direc- 
tion is advantageous. This concept is known as long 
centric. Schuyler" was one of the first to advocate 
such an occlusal arrangement. He thought that it 
was important for the posterior teeth to be in har- 
monious gliding contact when the mandible trans- 
lates from centric relation forward to make anterior 
tooth contact. Others 33 have advocated long centric 
because centric relation only rarely coincides with 
the maximum intereuspation position in healthy 
natural dentitions. However, its length is arbitrary. 
At given vertical dimensions, long centric ranges 
from 0.5 to 1.5 mm in length have been advocated. 
This theory presupposes that the condyles can 
translate horizontally in the fossae over a commen- 
surate trajectory before beginning to move down- 
ward. It also necessitates a greater horizontal space 
between the maxillary and mandibular anterior 
teeth (deeper lingual concavity), allowing horizon- 
tal movement before posterior disocclusion. 

MUTUALLY PROTECTED OCCLUSION 

During the early 1960s, an occlusal scheme called 
mutually protected occlusion was advocated by Stuart 
and Stallard, 4 based on earlier work by D'Amico.35 
In this arrangement, centric relation coincides with 
the maximum intereuspation position. The six ante- 
rior maxillary teeth, together with the six anterior 
mandibular teeth, guide excursive movements of 
the mandible, and no posterior occlusal contacts oc- 
cur during any lateral or protrusive excursions. 

The relationship of the anterior teeth, or anterior 
guidance, is critical to the success of this occlusal 
scheme. In a mutually protected occlusion, the pos- 
terior teeth come into contact only at the very end of 
each chewing stroke, minimizing horizontal load- 
ing on the teeth. Concurrently, the posterior teeth 
act as stops for vertical closure when the mandible 
returns to its maximum intereuspation position. 
Posterior cusps should be sharp and should pass 
each other closely without contacting to maximize 
occlusal function. Investigations of the neuromus- 
cular physiology of the masticatory apparatus indi- 
cate advantages associated with a mutually pro- 
tected occlusal scheme. 8 However, in studies 
involving unrestored dentitions, relatively few oc- 
clusions can be classified as mutually protected ^e 



I 



Section 1 Planning and Preparation 



Optimum Occlusion 

In an ideal occlusal arrangement, the load exerted 
on the dentition should be distributed optimally. Oc- 
clusal contact has been shown ^^ to influence muscle 
activity during mastication. Any restorative proce- 
dures that adversely affect occlusal stability may af- 
fect the timing and intensity of elevator muscle ac- 
tivity. Horizontal forces on any teeth should be 
avoided or at least minimized, and loading should 
be predominantly parallel to the long axes of the 
teeth. This is facilitated when the tips of the centric 
cusps are located centrally over the roots and when 
loading of the teeth occurs in the fossae of the oc- 
clusal surfaces rather than on the marginal ridges. 
Horizontal forces are also minimized if posterior 
tooth contact during excursive movements is 
avoided. Nevertheless, to enhance masticatory effi- 
ciency, the cusps of the posterior teeth should have 
adequate height. 

The chewing and grinding action of the teeth is 
enhanced if opposing cusps on the laterotrusive 
side interdigitate at the end of the chewing stroke. 
The mutually protected occlusal scheme probably 
meets this criterion better than the other occlusal 
arrangements. The features of a mutually protected 
occlusion are as follows31: 

1. Uniform contact of all teeth around the arch 
when the mandibular condylar processes are in 
their most superior position 

2. Stable posterior tooth contacts with vertically 
directed resultant forces 



3. Centric relation coincident with maximum in- 
tercuspation (intercuspal position) (CR = MI) 

4. No contact of posterior teeth in lateral or pro- 
trusive movements 

5. Anterior tooth contacts harmonizing with func- 
tional jaw movements 

In achieving these criteria, it is assumed that (1) a 
full complement of teeth exists, (2) the supporting 
tissues are healthy, (3) there is no cross bite, and (4) 
the occlusion is Angle Class I. 

Rationale. At first glance it might seem illogi- 
cal to load the single-rooted anterior teeth as op- 
posed to the multirooted posterior teeth during 
chewing. However, the canines and incisors have 
a distinct mechanical advantage over the posterior 
teeth^^: the effectiveness of the force exerted by the 
muscles of mastication is notably less when the 
loading contact occurs farther anteriorly. 

The mandible is a lever of the class III type (Fig. 
4-21), which is the least efficient of lever systems. 
An example of another class III lever would be a 
fishing pole. The longer the pole, the more effort it 
takes to pull a fish out of the water. The same holds 
true for the muscles of mastication and the teeth: the 
farther anteriorly initial tooth-to-tooth contact oc- 
curs (i.e., the longer the lever arm), the less effective 
will be the forces exerted by the musculature and 
the smaller the load to which the teeth are subjected. 
The canine-with its long root, significant amount 
of periodontal surface area, and strategic position in 




Fig. 4-21 . Lever system of the mandible. A, The elevator muscles of the mandible insert anterior to 
the TMJs and posterior to the teeth, forming a class III lever system. B, The fulcrum (F) is the TMJ, the 
force or effort (E) is applied by the muscles of mastication, and the resistance or load (L) is food placed 
between the teeth. The load will diminish as the lever arm increases. Therefore less load is placed on the 
anterior than on the posterior teeth. 



Chapter 4 Principles of Occlusion 



I 



the dental arch-is well adapted to guiding excur- 
sive movements. This function is governed by pres- 
soreceptors in the periodontal ligament, receptors 
that are very sensitive to mechanical stimulation." 
The elimination of posterior contacts during ex- 
cursions reduces the amount of lateral force to 
which posterior teeth are subjected. Therefore, mo- 
lars and premolars in group function are subjected 
to greater horizontal and potentially more patho- 
logic force than the same teeth in a mutually pro- 
tected occlusion. 



ig] PATIENT ADAPTABILITY 

There are significant differences in the adaptive re- 
sponse of patients to occlusal abnormalities. Some in- 
dividuals are unable to tolerate seemingly trivial oc- 
clusal deficiencies, whereas others are able to sustain 
distinct malocclusions without obvious symptoms. 
Most patients seem able to adapt to small occlusal 
deficiencies without exhibiting acute symptoms. 

LOWERED THRESHOLD 

Patients with a low pain threshold generally do not 
present much difficulty in diagnosis. They readily 
identify every pain. A lowered threshold, however, 
is not to be confused with hypochondria; it is 
merely an indication of poor adaptability to occlusal 
discrepancies. NOTE: The tolerance or adaptability 
of an individual patient will likely vary-it will be 
lower at times of emotional stress and general 
malaise, when clinical symptoms such as severe 
headaches, muscle spasm, and pain may surface. 

RAISED THRESHOLD 

Individuals who have adapted to existing malocclu- 
sions may report being quite comfortable with their 
dentition, although considerable symptoms are evi- 
dent. Even in the absence of pain, however, occlusal 
treatment may be advised to prevent or minimize 
wear on the teeth and damage to the musculature or 
temporomandibular joints. 

^] PATHOGENIC OCCLUSION 

A pathogenic occlusion is defined as an occlusal re- 
lationship capable of producing pathologic changes 
in the stomatognathic system. In such occlusions suf- 
ficient disharmony exists between the teeth and the 
TMJs to result in symptoms that require intervention. 

SIGNS AND SYMPTOMS 

There are many indications that a pathogenic occlu- 
sion may be present. Diagnosis is often complicated 
because patients almost always have a combination 



of symptoms. Although it is often not possible to 
prove a direct correlation between specific symp- 
toms and malocclusion, the following symptoms 
can help confirm this diagnosis. 

Teeth. The teeth may exhibit hypermobility, 
open contacts, or abnormal wear. Hypermobility of 
an individual tooth or opposing pair of teeth is of- 
ten an indication of excessive occlusal force. This 
may be due to premature contact in centric relation 
or during excursive movements. Such contacts fre- 
quently can be detected by placing the tip of the in- 
dex finger on the crown portion of the mobile tooth 
and asking the patient to repeatedly tap the teeth to- 
gether. Small amounts of movement (fremitus) that 
otherwise might not be readily seen often can be felt 
this way. 

Open proximal contacts may be the result of 
tooth migration because of an unstable occlusion 
and should prompt further investigation (Fig. 4-22). 
Diagnostic casts made during previous treatment 
will help assess any changes in the stability of the 
occlusion. Abnormal tooth wear, cusp fracture, or 
chipping of incisal edges may be signs of parafunc- 
tional activity 4^'^^ However, extensive tooth destruc- 
tion is often due to a combination of acid erosion 
and attrition 4345 In these cases, the acid may be from 
the diet (e.g., excessive citrus fruit consumption) 
or endogenous (due to regurgitation or frequent 
vomiting). 

Periodontium. There is no convincing evidence 
that chronic periodontal disease is caused directly 
by occlusal overload. However, a widened peri- 
odontal ligament space (detected radiographically) 
may indicate premature occlusal contact and is 
often associated with tooth mobility (Fig. 4-23). Sim- 
ilarly, isolated or circumferential periodontal de- 
fects are often associated with occlusal trauma. In 
patients with advanced periodontal disease who 




Fig. 4-22. Unstable occlusion. Removal of a tooth with- 
out replacement has led to tilting and drifting. 



I 



Section 1 Planning and Preparation 




Fig. 4-23. Widened periodontal ligament space and in- 
creased mobility of mandibular molars. Occlusal premature 
contacts were noted in lateral and protrusive movements. 



have extensive bone loss, rapid tooth migration may 
occur with even minor occlusal discrepancies. Tooth 
movement may make it difficult for these patients to 
institute proper oral hygiene measures, and the re- 
sult may be a recurrence of periodontal disease. Pre- 
cise adjustment of the occlusion is probably more 
critical in patients with a compromised crown/root 
ratio than in those with better periodontal support 
(see Chapter 32). 

Musculature. Acute or chronic muscular pain 
on palpation can indicate habits associated with 
tension such as bruxing or clenching. Chronic 
muscle fatigue can lead to muscle spasm and pain. 
In one study, subjects were instructed to grind 
their teeth for approximately 30 minutes. They ex- 
perienced muscle pain that typically peaked 2 hours 
after parafunctioning and lasted as long as 7 days. 
Asymmetric muscle activity can be diagnosed by 
observing a patient's opening and closing move- 
ments in the frontal plane. A deviation of a few mil- 
limeters is quite common, but anything beyond this 
calls for further examination (Fig. 4-24) and may be 
a sign of dysfunction.47 Restricted opening, or tris- 
mus, may be due to the fact that the mandibular el- 
evator muscles are not relaxing. 

Temporomandibular Joints. Pain, clicking, or 
popping in the TMJs can indicate TM disorders. 
Clicking and popping may be present without the 
patient's awareness. A stethoscope is a useful diag- 
nostic aid; a recent study found joint sounds are 
generally reliable indicators of temporomandibular 
disorders 4 s The patient may complain of TMJ pain 
that is actually of muscular origin and is referred to 
the joints. 



!TT5 



10 mm - 



20 mm - 



30 mm — 



)*- — Path of opening 



( 




Fig. 4-24. Midline deviation during opening and closing 
movements can be indicative of asymmetric muscle activity 
or joint derangement. Here, during opening, less than opti- 
mal translation occurs on the patient's left side. 



Clicking may also be associated with internal de- 
rangements of the joint. A patient with unilateral 
clicking when opening and closing (reciprocal click) 
in conjunction with a midline deviation may have 
a displaced disk. The midline deviation will typi- 
cally occur toward the side of the affected joint 
because the displaced disk can prevent (or slow 
down) the normal anterior translatory movement of 
the condyle. 

Myofascial Pain Dysfunction. The myofascial 
pain dysfunction (MPD) syndrome presents as dif- 
fuse unilateral pain in the preauricular area, with 
muscle tenderness, clicking, or popping noises in the 
contralateral TMJ and limitation of jaw function. 
Often the muscles, and not the TMJ, are the primary 
site, but over time the functional problem may lead 
to organic changes in the joint. Three major theories 
relative to the cause of MPD are recognized: The 
psychophysiologic theory49 states that MPD results 
from bruxing and clenching, with chronic muscle fa- 
tigue leading to muscle spasm and altered mandibu- 
lar movement. Tooth movement may follow, and the 
malocclusion becomes apparent when spasm is re- 
heved. According to this theory, treatment should fo- 
cus on emotional rather than physical therapy. 



Fin^nr-f!? 



Chapter 4 Principles of Occlusion 



The muscle theory50 states that continuous mus- 
cle hyperactivity is responsible for MPD, with pain 
referred to the TMJ and other areas of the head and 
neck region. 

The mechanical displacement theory5 1 states that 
malocclusion of the teeth displaces the condyles, 
and the feedback from the dentition is altered, 
which results in muscle spasm. 

Correct diagnosis and management is often 
complicated by the concurrent presence of multiple 
etiologies. Patients with MPD may require multi- 
disciplinary treatment involving occlusal therapy, 
medications, biofeedback, and physical therapy. Ex- 
tensive fixed prosthodontic treatment should be 
postponed until the patient's condition(s) have been 
stabilized at acceptable levels. 



^1 OCCLUSAL TREATMENT 

When a patient exhibits signs and symptoms that 
appear correlated to occlusal interferences (see also 
p. 157), occlusal treatment should be considered.52 
Such treatment can include tooth movement 
through orthodontics, elimination of deflective oc- 
clusal contacts through selective reshaping of the 
occlusal surfaces of teeth, or the restoration and re- 
placement of missing teeth resulting in more favor- 
able distribution of occlusal force. 

The objectives of occlusal treatment are as follows: 

1. To direct the occlusal forces along the long 
axes of the teeth 

2. To attain simultaneous contact of all teeth in 
centric relation 

3. To eliminate any occlusal contact on inclined 
planes to enhance the positional stability of 
the teeth 

4. To have centric relation coincide with the 
maximum intercuspation position 

5. To arrive at the occlusal scheme selected for 
the patient (e.g., unilateral balanced versus 
mutually protected) 

In the short term, these objectives can be accom- 
plished with a removable occlusal device (Fig. 4-25) 
fabricated from clear acrylic resin that overlays the 
occlusal surfaces of one arch. On a more permanent 
basis, this can be accomplished through selective 
occlusal reshaping, tooth movement, the placement 
of restorations, or a combination of these. Definitive 
occlusal treatment involves accurate manipulation 
of the mandible, particularly in centric relation. Be- 
cause the patient may resist such manipulation as a 
result of protective muscular reflexes, some type of 
deprogramming device may be needed (e.g., an oc- 
clusal device). 




Fig. 4-25. Occlusal device. 

(Courtesy Dr. WV. Campagni.) 



OCCLUSAL DEVICE THERAPY 

Occlusal devices (sometimes referred to as occlusal 
splints, occlusal appliances, or orthotics) are exten- 
sively used in the management of TM disorders 
and bruxism." In controlled clinical trials, they 
have effectively controlled myofascial pain (i.e., 
the patient's perceived positive changes as a result 
of the device therapy). However, no clear hypoth- 
esis about the mechanism of action has been 
proved, and none of the various hypotheses (repo- 
sitioning of condyle and/or the articular disk, re- 
duction in masticatory muscle activity, modifica- 
tion of "harmful" oral behavior, and changes in the 
patient's occlusion) has been consistently sup- 
ported by scientific studies 54 Occlusal devices are 
particularly helpful in determining whether a pro- 
posed change in a patient's occlusal scheme will be 
tolerated. The proposed scheme is created in an 
acrylic resin overlay, which allows testing of the 
scheme through reversible means, although at a 
slightly increased vertical dimension. If a patient 
responds favorably to an occlusal device, the re- 
sponse to restorative treatment should be positive 
as well. Thus, occlusal device therapy can serve as 
an important diagnostic procedure before initia- 
tion of fixed prosthodontic treatment. The device 
can be made for either maxillary or mandibular 
teeth. Some clinicians express a preference for one 
or the other and cite advantages; however, both 
maxillary and mandibular devices have proved 
satisfactory. 

Fabricatson of Device 

There are several satisfactory methods for making 
an occlusal device . 44 One made from heat-polymer- 
ized acrylic resin will have the advantage of dura- 
bility, but autopolymerizing resin used alone or in 
conjunction with a vacuum- formed matrix can 
serve equally well. Box 4-1 compares the indirect 
and direct techniques. 




Section 1 Planning and Preparation 



! Comparison of 
Occlusal Devices 


BOX 4-1 


More eithetie— plastic is 


Can be done in one 


' crystal dear 


oppointment 


More dense, less subject to 


Uses the mouth as an 


breakage, warping, or 


articulator, introducing 


wear 


errors 


' More precise occlusal con- 


Vacuum-brmed matrix is 


tocts with use of 


tfiin and flexible^ requir- 


articulator 


ing more coverage for 


Less chair time at delivery 


stability 


Better adaptation to teetfi 


Cfiipping and breaking ~ 


and soft tissues 


need for choirside 


Increased laboratory cost 


repairs 


(waxing, tasking, 


Stain, odors, and excess 


Finbhing) 


wear because of porosity 


Better control of bulk 


of acrylic 


Less coverage needed for 


Device can be duplicated , 


stobiiity 


in fieat polymerized 


Use of boll clasps fof 


resin for greoter 


retention 


durability 



Courtt:iy Dr. jiitnes E. Pctm; 



Direct Procedure Using 
a Vacuum-Formed Matrix 

1. Adapt a sheet of clear thermoplastic resin to 
a diagnostic cast using a vacuum- forming 
machine. Hard resin (I nom thick) is suit- 
able. Be sure that excessive undercuts have 
been blocked out. Trim the excess resin so all 
facial soft tissues are exposed. On the facial 
surfaces of the teeth, the device must be 
kept well clear of the gingival margins (Fig. 
4-26, A). On the lingual surface of maxillary 
devices, the matrix should cover the ante- 
rior third of the hard palate for rigidity. 

2. Try in the matrix for fit and stability. Add a 
small amount of autopolymerizing acrylic 
resin in the incisal region. Guide the 
mandible into CR using the bimanual ma- 
nipulation technique (see Chapter 2). Hinge 
the mandible to make shallow indentations 
in the resin (Fig. 4-26, B). 

3. Add more resin to the incisor and canine re- 
gions and guide the patient to retrusive, 
protrusive, and lateral closures in the soft 
resin. Allow the resin to polymerize. NOTE: 
The resin should be allowed to polymerize 
on the cast or with the appliance in place in 
the mouth. Otherwise, the heat generated 
by polymerization may distort the thermo- 
plastic matrix. 



4. With the help of marking ribbon, adjust the 
resin to give smooth, even contacts during 
protrusive and lateral excursions as well as 
a definite occlusal stop for each incisor in 
centric relation (Fig. 4-26, C). Confine pro- 
trusive contacts to the incisors and lateral 
contacts to the laterotrusive canines (Fig. 
4-26, D). All posterior contacts should be re- 
lieved at this stage. 

5. Have the patient wear the device for a few 
minutes in the office. Repeated protrusive 
and lateral movements will overcome most 
problems in jaw manipulation. Occasionally 
it will be necessary for the patient to wear 
the device overnight before the acquired 
protective muscle patterns are overcome. 
NOTE: In such cases, if posterior tooth erup- 
tion is to be avoided, the patient must be 
seen again within 24 to 48 hours. 

6. Add autopolymerizing acrylic resin to the 
posterior region of the device and guide the 
patient into centric relation. Hold CR until 
the acrylic resin has polymerized. 

7. Remove the device and examine the impres- 
sions of the opposing arch in the resin (Fig. 
4-26, E). Polymerization can be accelerated 
by placing the device on the cast in warm 
water in a pressure pot (Fig. 4-26, F). 

8. Place pencil marks in the depressions 
formed by the opposing centric cusps. If a 
cusp registration is missing, new resin can 
be added and the device reseated. 

9. Remove excess resin with a bur or wheel to 
leave only the pencil marks (Fig. 4-26, G). 
All other contacts must be eliminated if pos- 
terior disclusion is to be achieved. 

10. Check the device in the mouth for CR con- 
tacts, marking them with a ribbon. Relieve 
heavy contacts by continued adjustment un- 
til each centric cusp has an even mark. 

11. Identify protrusive and lateral excursions 
using different-colored tape. Adjust excur- 
sive contacts as necessary, being careful not 
to remove the centric cusp stops. 

12. Smooth and polish the device, again being 
careful not to alter the functional surfaces 
(Fig. 4-26, H). 

13. After a period of satisfactory use, the device 
can be duplicated in heat-polymerized resin 
using a standard denture reline technique. 

Indirect Procedure Using Autopolymerizing 
Acrylic Resin 

Accurately mounted diagnostic casts are essential 
for this procedure. A relatively small mounting er- 



Chapter 4 Principles of Occlusion 
B C 



I 




Fig. 4-26. Direct procedure for the fabrication of an occlusal device. 



ror can lead to considerable loss of time at try-in. 4. 

Particular attention must be given to occlusal de- 
fects or interfering soft tissue projections on the 
casts, which could cause errors during mounting. 5. 

1. Be sure that the device is made at the same 
vertical dimension of occlusion as the CR 
record. This will reduce mounting errors de- 
rived from using an arbitrary facebow. 6. 

2. Fit the articulator with a mechanical incisal 
guidance table initially set flat. 

3. Lower the incisal guide pin until there is ap- 
proximately 1 mm of clearance between the 
posterior teeth (Fig. 4-27, A). This should be 7. 
the same vertical dimension of occlusion as 

the one at which the CR record was made. 



Depending on the type of articulator used, it 
may be necessary to reposition the incisal 
guide table after step 3. 
Check the clearance between opposing casts 
during protrusive movement of the articula- 
tor. Where this is less than 1 mm, increase it 
by tilting the incisal guidance table. 
Raise the platform wings of the incisal guid- 
ance table so there is at least 1 mm of clear- 
ance in all lateral excursions (Fig. 4-27, B). It 
may be necessary to raise the incisal pin oc- 
casionally to ensure adequate clearance. 
Mark the height of contour of each tooth on 
the cast and block out undercuts with wax 
(Fig. 4-27, C. 



I 



Section 1 Planning and Preparation 



D,E 




Fig. 4-27. A to J, Indirect procedure with autopolymerizing resin for the fabrication of an occlusal device. 



9. 



Form wire clasps to engage facial under- 
cuts and seal the cast with a separating 
medium (e.g., Al-Cote) and allow it to dry 
(Fig. 4-27, D). The opposing cast can be 
soaked in water to prevent the acrylic resin 
from sticking to it. 

Fabricate the device with autopolymerizing 
clear acrylic resin (Fig. 4-27, E) applied by 



alternating liquid and powder (Fig. 4-27, F). 
To avoid porosities, the resin should always 
be kept wet with monomer and added in 
small increments (Fig. 4-27, G). 
10. While the resin is still soft, close the articu- 
lator (Fig. 4-27, H). Add resin where neces- 
sary until a slight depression is formed by 
each centric cusp. 



Chapter 4 Principles of Occlusion 



I 



11. 



12. 



13. 



Again, while the resin is still soft, close the 
articulator into protrusive and lateral excur- 
sions. Add or remove resin until it is in con 
stant contact with the anterior teeth when 
the incisal guide pin contacts the incisal 
guidance table. This adjustment need only 
be approximate because the working time of 
the acrylic resin is limited and the occlusal 
contacts will be refined after the resin has 
polymerized. 

Place the device and cast in warm water in a 
pressure vessel to polymerize. When this is 
complete, flush wax from the cast with boil- 
ing water. 
Refine the occlusion on the articulator (Fig. 



a. There should be even contact for each 
centric cusp in centric relation. 

b. A stop should exist for each anterior 
tooth in CR. 

c. Protrusive contact on the incisors 
should be smooth and even. 

d. There should also be smooth and even 
lateral contact on the laterotrusive 
(working- side) canines. 

14. Remove the device from the cast and 
smooth and polish it, taking care not to alter 
the functional surfaces (Fig. 4-27, J). 

15. At try-in, check for fit and stability. Also 
check the occlusal contacts and adjust as 
necessary, using different-colored marking 
ribbon for centric and eccentric contacts. 

Indirect Procedure Using Heat-polymerized 
Acrylic Resin 

A more durable device can be made with heat- 
polymerized acrylic resin. The desired occlusal sur- 
face is shaped in wax on articulated diagnostic casts, 
or the direct device made with a vacuum- formed 
matrix can be used as a pattern. This is flasked and 
processed in a manner similar to that for a complete 
denture. Because of processing errors, it is important 
to remount the cast and make necessary adjustments 
before finishing and polishing are completed. 

1. Articulate the casts in CR. Allow for a re- 
mount procedure by notching the base of the 
cast on which the device will be processed. 

2. Create the desired configuration of the device 
in wax, obtaining centric stops and anterior 
guidance. Use the mechanical anterior guid- 
ance table as for an autopolymerizing resin 
device. 

3. Separate the cast from its mounting and flask 
as for conventional processing of complete 
dentures. 



4. Process in clear, heat-cured resin. 

5. Re articulate and adjust the occlusion. 

6. Remove the stone cast with a shell blaster. 
Polish the external surfaces on a lathe with 
pumice and an appropriate polishing com- 
pound. 

7. Store in 100% humidity. 

Attention to Detail 

Regardless of the device chosen, success depends 
very much on meticulous attention to detail during 
the fabrication. When making a direct device, use a 
well-adapted and stable vacuum- formed base and 
follow the procedure exactly. For example, be sure 
that the anterior guidance is properly established 
and that the patient's jaw can be easily manipulated 
before adding resin to the posterior region. When 
the indirect procedure is used, be sure that the casts 
articulate to an accurate CR record made at the cor- 
rect vertical dimension of occlusion. Inaccurate 
mounting is probably the most common cause for 
frustration and results in excessive adjustments at 
delivery. 

FOLLOW-UP 

After delivery to the patient, the occlusion must be 
verified and corrected as necessary. The patient is 
instructed to wear the device 24 hours a day, re- 
moving it only for oral hygiene, and to return at reg- 
ular weekly and biweekly intervals (or sooner if a 
problem is anticipated) for modification. A reduc- 
tion in discomfort suggests that definitive occlusal 
adjustment (see Chapter 5) or restorative dentistry, 
or both, will likely be successful. If device therapy 
fails to relieve the discomfort, further evaluation 
and diagnosis of the etiology and parameters of the 
chief complaint should be pursued. 

{^SUMMARY 

Mandibular movement depends on certain ana- 
tomic limitations. The extremes, called border move- 
ments, are subject to restriction by the temporo- 
mandibular joints and ligaments and the teeth. 
Speech and mastication are examples of functional 
movements. Bruxism and clenching are examples of 
parqfunctioncd movements. These accomplish no pur- 
poseful objective and are potentially harmful. 

A balanced occlusion provides complete denture 
patients with stability, because there is even contact 
between all the teeth in each excursion. This is poten- 
tially destructive in dentate patients and is not indi- 
cated for fixed prosthodontic treatment. In a unilater- 
ally balanced occlusion (group function), eccentric 
occlusal contact occurs only between posterior teeth 



I 



Section 1 Planning and Preparation 



on the laterotrusive (working) side. This may be indi- 
cated when it is important to distribute the occlusal 
load over multiple teeth. The mutually protected oc- 
clusion offers the most desirable distribution of oc- 
clusal load. Centric relation coincides with the maxi- 
mum intercuspation position, and the relationship of 
the maxillary and mandibular anterior teeth (the an- 
terior guidance) is instrumental to its success. 

In the presence of pathology that is potentially re- 
lated to malocclusion, occlusal therapy may be indi- 
cated. Occlusal devices can serve as useful diagnos- 
tic and therapeutic adjuncts to treatment. For such 
patients, occlusal therapy should be initiated and 
completed before any substantial restorative care is 
undertaken. 



awssAno} 




Angle's classification of occlusion: [Edward Harley 
Angle, American orthodontist, 1855-1930]: eponym 
for a classification system of occlusion based on the 
interdigitation of the first molar teeth originally de- 
scribed by Angle as four major groups depending 
on the anteroposterior jaw relationship. Class IV is 
no longer used. Class I (normal occlusion or neu- 
trocclusion): the dental relationship in which there 
is normal anteroposterior relationship of the jaws, 
as indicated by correct interdigitation of maxillary 
and mandibular molars, but with crowding and ro- 
tation of teeth elsewhere, i.e., a dental dysplasia or 
arch length deficiency. Class 11 (distocclusion): the 
dental relationship in which the mandibular dental 



arch is posterior to the maxillary dental arch in one 
or both lateral segments; the mandibular first molar 

is distal to the maxillary first molar. Further subdi- 
vided into two divisions. Division 1: bilateral distal 
retrusion with a narrow maxillary arch and pro- 
truding maxillary incisors. Subdivisions include 
right or left (unilaterally distal with other character- 
istics being the same). Division 2: bilateral distal 
with a normal or square- shaped maxillary arch, 
retruded maxillary central incisors, labially mal- 
posed maxillary lateral incisors, and an excessive 
vertical overlap. Subdivisions include right or left 
(unilaterally distal with other characteristics the 
same). Class III (mesiocclusion): the dental relation- 
ship in which the mandibular arch is anterior to the 
maxillary arch in one or both lateral segments; the 
mandibular first molar is mesial to the maxillary 
first molar. The mandibular incisors are usually in 
anterior cross-bite. Subdivisions include right or left 
(unilaterally mesial with other characteristics the 
same). Class IV: the dental relationship in which the 
occlusal relations of the dental arches present the 
peculiar condition of being in distal occlusion in 
one lateral half and in mesial occlusion in the other 
(no longer used). (Angle EH. Classification of mal- 
occlusion. Dental Cosmos 1899; 41:248-64, 350-7.) 

anterior open occlusal relationship: the lack of anterior 
tooth contact in any occluding position of the pos- 
terior teeth 

arc of closure: the circular or elliptic arc created by clo- 
sure of the mandible, most often viewed in the 
mid-sagittal plane, using a reference point on the 
mandible (frequently either mandibular central in- 
cisors' mesial incisal edge). 



Sf^dy Que^iiam 



T, Discuss the various functions of the mandibular ligaments and relate them to their respective origins and 
insertions. 

2. Discuss the various functions of the mandibular muscles and relate them to their respective origins and in- 
sertions. 

3. What are border movements? Draw and label Posselt's solid. 

4. What are the determinants of occlusion and what do they determine? 

5. Give examples of pathologic occlusion and list five categorJes with multiple associated symptoms for each 
category. 

6. Describe a mutually protected occlusal scheme, its advantages, and indications. When is a mutually prc^ 
tected occiusion undesirable? Why? 

7. Discuss typical mandibular movement during normal function ond during parafunction. What is the influ- 
ence of age on chewing patterns? 

8. What is the difference between a bilateral balanced occlusion, a unilateral balanced occlusion, and mu- 
tual protection? 

9. What are the purposes of an occlusal device? Describe a scenario fustifying jts use, and explain how the 
device should be designed. Explain your rationale for this design. 



Chapter 4 Principles of Occlusion 



I 



arthrodial joint: a joint that allows gliding motion of 
the surfaces. 

attrition: (n) (14c) 1: the act of wearing or grinding 
down by friction 2: the normal mechanical wear re- 
sulting from mastication, limited to contacting sur- 
faces of the teeth 

balanced articulation: the bilateral, simultaneous, an- 
terior, and posterior occlusal contact of teeth in cen- 
tric and eccentric positions. 

Bennett angle: obs: the angle formed between the 
sagittal plane and the average path of the advanc- 
ing condyle as viewed in the horizontal plane dur- 
ing lateral mandibular movements (GPT-4). 

border movement: mandibular movement at the limits 
dictated by anatomic structures, as viewed in a 
given plane. 

bruxism: (n) (ca. 1940) 1: the parafunctional grinding 
of teeth 2: an oral habit consisting of involuntary 
rhythmic or spasmodic nonfunctional gnashing, 
grinding, or clenching of teeth, in other than chew- 
ing movements of the mandible, which may lead to 
occlusal trauma-called also tooth grinding, oc- 
clusal neurosis. 

canine protected articulation: a form of mutually pro- 
tected articulation in which the vertical and hori- 
zontal overlap of the canine teeth disengage the 
posterior teeth in the excursive movements of the 
mandible. 

capsular ligament: within the temporomandibular 
joint, a ligament that separately encapsulates the 
superior and inferior synovial cavities of the tem- 
poromandibular articulation. 

capsule: (n) (1693): a fibrous sac or ligament that en- 
closes a joint and limits its motion. It is lined with 
synovial membrane. 

clenching: (vt) (13c): the pressing and clamping of the 
jaws and teeth together, frequently associated with 
acute nervous tension or physical effort. 

determinants of mandibular movement: those ana- 
tomic structures that dictate or limit the movements 
of the mandible. The anterior determinant of 
mandibular movement is the dental articulation. 
The posterior determinants of mandibular move- 
ment are the temporomandibular articulations and 
their associated structures. 

disk: n (1664): with respect to the temporomandibular 
joint, the avascular interarticular tissue (spelled also 
disc). 

elevator muscle: one of the muscles that, on contract- 
ing, elevates or closes the mandible. 

envelope of motion: the three-dimensional space cir- 
cumscribed by mandibular border movements 
within which all unstrained mandibular movement 
occurs. 

frontal plane: any plane parallel with the long axis of 
the body and at right angles to the median plane, 
thus dividing the body into front and back parts. So 



called because this plane roughly parallels the 
frontal suture of the skull. 

group function: multiple contact relations between the 
maxillary and mandibular teeth in lateral move- 
ments on the working side whereby simultaneous 
contact of several teeth act as a group to distribute 
occlusal forces. 

horizontal overlap: the projection of teeth beyond 
their antagonists in the horizontal plane 

incisal guidance: 1: the influence of the contacting sur- 
faces of the mandibular and maxillary anterior teeth 
on mandibular movements 2: the influence of the 
contacting surfaces of the guide pin and guide table 
on articulator movements. 

intercondylar distance: the distance between the rota- 
tional centers of two condyles or their analogues. 

laterotrusion: (n): condylar movement on the working 
side in the horizontal plane. This term may be 
used in combination with terms describing con- 
dylarmovement in other planes, for example, lat- 
erodetrusion, lateroprotrusion, lateroretrusion, and 
laterosurtrusion. 

malocclusion: (n) (1888) 1: any deviation from a physi- 
ologically acceptable contact of opposing dentitions 
2: any deviation from a normal occlusion. 

mandibular hinge position: (obs): the position of the 
mandible in relation to the maxilla at which open- 
ing and closing movements can be made on the 
hinge axis (GPT-4). 

mandibular translation: the translatory (medio-lateral) 
movement of the mandible when viewed in the 
frontal plane. While this has not been demonstrated 
to occur as an immediate sideward movement 
when viewed in the frontal plane, it could theoreti- 
cally occur in an essentially pure translatory form in 
the early part of the motion or in combination with 
rotation in the latter part of the motion or both. 

masticatory cycle: a three dimensional representation 
of mandibular movement produced during the 
chewing of food. 

mutually protected articulation: an occlusal scheme in 
which the posterior teeth prevent excessive contact 
of the anterior teeth in maximum intercuspation, 
and the anterior teeth disengage the posterior teeth 
in all mandibular excursive movements. 

occlusal balance: a condition in which there are simul- 
taneous contacts of opposing teeth or tooth ana- 
logues (i.e., occlusion rims) on both sides of the 
opposing dental arches during eccentric move- 
ments within the functional range 

occlusal contact: 1: the touching of opposing teeth on 
elevation of the mandible 2: any contact relation of 
opposing teeth. 

open occlusal relationship: the lack of tooth contact in 
an occluding position. 

opening movement: (obs) movement of the mandible 
executed during jaw separation (GPT-1). 



I 



Section 1 Planning and Pr eparation 



paraf unction: (adj): disordered or perverted function. 

pathogenic occlusion: an occlusal relationship capable 
of producing pathologic changes in the stomatog- 
nathic system. 

posterior border movement: movements of the mandible 
along the posterior Hmit of the envelope of motion. 

protrusion: (n) (1646): a position of the mandible ante- 
rior to centric relation. 

retrodiscal tissue: a mass of loose connective tissue at- 
tached to the posterior edge of the articular disk 
and extending to and filling the loose folds of the 
posterior capsule of the temporomandibular joint- 
called also bilaminar zone. 

retruded contact position: that guided occlusal relation- 
ship occurring at the most retruded position of the 
condyles in the joint cavities. A position that may be 
more retruded than the centric relation position. 

rotation: (n) (7555) 1: the action or process of rotating 
on or as if on an axis or center 2: the movement of a 
rigid body in which the parts move in circular paths 
with their centers on a fixed line called the axis of 
rotation. The plane of the circle in which the body 
moves is perpendicular to the axis of rotation. 

sagittal plane: any vertical plane or section parallel to 
the median plane of the body that divides a body 
into right and left portions. 

synovial fluid : a viscid fluid contained in joint cavities 
and secreted by the synovial membrane 

temporomandibular joint: 1: the articulation between 
the temporal bone and the mandible. It is a diarthro- 
dial, bilateral ginglymus arthrodial joint 2: the articu- 
lation of the condylar process of the mandible and 
the interarticular disk with the mandibular fossa of 
the squamous portion of the temporal bone; a di- 
arthrodial, sliding hinge (ginglymus) joint. Move- 
ment in the upper joint compartment is mostly trans- 
lational, whereas that in the lower joint compartment 
is mostly rotational. The joint connects the mandibu- 
lar condyle to the articular fossa of the temporal bone 
with the temporomandibular disk interposed. 

translation: (n) (Mc): that motion of a rigid body in 
which a straight line palling through any two points 
always remains parallel to its initial position. The mo- 
tion may be described as a sliding or gUding motion. 

transverse horizontal axis: an imaginary line around 
which the mandible may rotate within the sagittal 
plane. 
vertical overlap: 1: the distance teeth lap over their an- 
tagonists as measured vertically; especially the dis- 
tance the maxillary incisal edges extend below 
those of the mandibular teeth. It may also be used to 
describe the vertical relations of opposing cusps 
2: the vertical relationship of the incisal edges of the 
maxillary incisors to the mandibular incisors when 
the teeth are in maximum intercuspation. 
working side the side toward which the mandible 
moves in a lateral excursion. 



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40. 
41. 

42. 
43. 



45. 



46. 



47. 



49. 



50. 



51. 



52. 



53. 



54. 



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Ch 75. 

Dao TT, Lavigne GJ: Oral splints: the crutches 
for temporomandibular disorders and bruxism? 

Crit Rev Oral Biol Med 9:345, 1998. 



m^:-mmmm-imMm: 






Periodontal Considerations 



Robert F. Banna 



mm^so^^mmsii 



attached gingiva 

bifurcation 

debridement 

gingiva 

guided tissue regeneration 

hemisection 



i nterdental papillae 
marginal gingiva 
mucogingival junction (MGJ) 
occlusal trauma 
reflection 
Sharpey's fibers 



In the fabrication of any fixed prosthesis, the practi- 
tioner must determine the periodontal status of the 
involved abutment teeth. This allows a reliable and 
accurate prognosis for the restoration. Because peri- 
odontal disease is a major cause of tooth loss in 
adults, the practitioner must be aware of the basic 
concepts and clinical modes of therapy available in 
periodontics to be able to develop an appropriate 
diagnosis and treatment plan. 

This chapter reviews these concepts and treat- 
ment modalities and gives the practitioner a better 
understanding of periodontics and how it relates to 
restorative dentistry. 



5] ANATOMY 



The lining of the oral cavity consists of three types 
of mucosa, each with a different function': 

1. Masticatory (keratinized) mucosa-covering 
the gingiva and hard palate 

2. Lining or reflecting mucosa-covering the 
lips, cheeks, vestibule, alveoli, floor of the 
mouth, and soft palate 

3. Specialized (sensory) mucosa-covering the 
dorsum of the tongue and taste buds 

GINGIVA 

Normal gingiva (Fig. 5-l)-exhibiting no fluid exu- 
date or inflammation due to bacterial plaque-is 
pink and stippled. It varies in width from 1 to 9 mm 
and extends from the free margin of the gingiva to 
the alveolar mucosa. The gingivae and alveolar mu- 
cosa are separated by a demarcation called the 
mucogingival junction (MGJ), which marks the dif- 
ferentiation between stippled keratinized tissue and 



smooth, shiny mucosa; the latter contains more elas- 
tic fibers in its connective tissue. Apical to the MGJ, 
the alveolar mucosa then forms the vestibule and at- 
taches to the muscles and fascia of the lips and 
cheeks. 

The gingiva (Fig. 5-2) consists of three parts: 
1. Free (marginal) gingiva-extending from the 
most corona' aspect of the gingiva to the ep- 
ithelial attachment with the tooth 




Fig. 5-1 . Normal gingiva. 




Fig. 5-2. Normal gingival structure and anatomic land- 
marks. MG, Marginal gingiva; fgg, free gingival groove; 
AG, attached gingiva; MG], mucogingival junction; AM, 
alveolar mucosa. 

(Redrawn from Schluger S et al: Periodontal disease, ed 2, 
Philadelphia, 1990, Lea & Febiger.) 



108 



Chapter 5 Periodontal Considerations 



I 



2. Attached gingiva-extending from the level 
of the epithelial attachment to the junction 
between the gingiva and the alveolar mucosa 
(the MGJ) 

3. Interdental papillae- triangular projections 
of gingivae filling the area between adjacent 
teeth and consisting of a buccal and a lingual 
component separated by a central concavity 
(the col) 

A V-shaped depression on the labial or buccal 

surface of the gingiva at or somewhat apical to the 

level of the epithelial attachment to the tooth is 

called thefree gingival groove. It is not always readily 

apparent clinically but can be seen histologically 

and may serve as a reference point for dividing 

the free gingiva from the labial or buccal- attached 
gingiva. 

The gingiva consists of dense collagen fibers, 
sometimes referred to as the gingivodental ligament, 
which can be divided into alveologingival, den- 
togingival, circular, dentoperiosteal, and transseptal 
groups. These fibers firmly bind the gingiva to the 
teeth and are continuous with the underlying alve- 
olar periosteum. A more detailed description can be 
found in standard periodontal texts .4-8 

PERIODONTIUM 

The periodontium is a connective tissue structure at- 
tached to the periosteum of both the mandible and 
the maxillae that anchors the teeth in the mandibu- 
lar and maxillary alveolar processes. It provides at- 
tachment and support, nutrition, synthesis and re- 
sorption, and mechanoreception. The main element 
of the periodontium is the periodontal ligament 
(PDL), which consists of collagenous fibers embed- 
ded in bone and cementum, giving support to the 
tooth in function (Fig. 5-3). These fibers, also known 
as Sharpey's fibers, follow a wavy course and ter- 
minate in either cementum or bone. There are five 
principal fiber groups in the PDL that traverse the 
space between the tooth root and alveolar bone, pro- 
viding attachment and support.' 

1. Transseptal fibers-extending interproximally 
between adjacent teeth (Their ends are embed- 
ded in cementum.) 

2. Alveolar crest fibers-beginning just apical to 
the epithelial attachment and extending from 
cementum to the alveolar crest 

3. Horizontal fibers-coursing at right angles from 
cementum to the alveolar bone 

4. Oblique fibers -extending in an oblique direc- 
tion apically, attaching cementum to the alveo- 
lar bone (They are the most numerous fibers.) 

5. Apical fibers -radiating from cementum into 
the alveolar bone at the apex of the root 



There are also smaller, irregularly arranged colla- 
gen fibers interspersed between the principal fiber 
groups. In addition, the PDL contains elastic fibers' 
as well as oxytalan fibers, lo 

Cellular elements found in the PDL include fi- 
broblasts (the main synthetic cell, producing colla- 
gen and other proteoglycans), cementoblasts and 
cementoclasts, osteoblasts and osteoblasts (main- 
taining the viability of their respective tissues), and 
mast cells and epithelial rests (playing a role in 
pathologic conditions of the periodontium).' 

DENTOGINGIVAL JUNCTION 

At the base of the gingival sulcus (crevice) is the 
epithelium- tooth interface, also known as the den- 
to gingival junction (DGJ). This structural relationship 
between hard and soft tissues is unique in the 
body. At the ultrastructural level, it is made up of 
hemidesmosomes and a basal lamina, which anchor 
the epithelial cells to the enamel and cemental 
surfaces 4 11 

The depth of the sulcus varies in healthy individ- 
uals, averaging 1.8 mm. 12 In general, the shallower 
it is, the more likely the gingiva will be in a state of 
health. Sulcular depths up to 3 mm are considered 
maintainable. The continued maintenance of the 
gingiva in a state of health depends on tight, shal- 
low sulci, which in turn depend on optimal plaque 
control, and will ensure the success of periodontal 
therapy as well as affording a good prognosis for 
subsequent restorative treatment. 




PDL 



-7*^=^ 



Fig. 5-3. Normal tooth-gingival interface and coronal 
periodontium. CEI, Cementoenamel junction; pdl, peri- 
odontal ligament; B, bone; C, cementum. 



I 



Section 1 Planning and Preparation 
^DISEASES OF THE PERIODONTIUM 

The general term periodontal disease is used to de- 
scribe any condition of the periodontium other than 
normal. It covers such pathologic states as gingival 
hyperplasia, juvenile periodontitis (also known as 
periodontosis), and acute necrotizing ulcerative gin- 
givitis-all distinct clinical entities that warrant spe- 
cific treatment. For information concerning these 
disease states, refer to any of the standard peri- 
odontal texts. Periodontal disease must be recog- 
nized and treated before fixed prosthodontics so 
that the gingival tissue levels can be determined to 
proper margin placement, esthetics, and gingival 
displacement (with an AIC13 -impregnated or plain 
cord, see Chapter 14). Only when the gingiva and 
periodontium are in an optimal state of health can 
these determinations be made with ease or pre- 
dictability. 

This discussion is limited to the etiology and pro- 
gression of the inflammatory gingivitis -periodonti- 
tis lesion, which affects the majority of adults i^ and 
constitutes the bulk of pathologic disorders needing 
treatment before restorative dentistry. 

ETIOLOGY 

Most gingival and periodontal diseases result from 
microbial plaque, which causes inflammation and 
its subsequent pathologic processes. Other contrib- 
utors to inflammation include calculus, acquired 
peUicle, materia alba, and food debris. 14 

Terminology 

Microbial Plaque. Microbial plaque (Fig. 5-4) 
is a sticky substance composed of bacteria and their 
by-products in an extracellular matrix; it also con- 
tains substances from the saliva, diet, and serum. It 
is basically a product of the growth of bacterial 
colonies and is the initiating factor in gingival and 
periodontal disease. If left undisturbed, it will grad- 




Fig. 5-4. Gross plaque and calculus accumulation on the 
mandibular anterior teeth. 



ually cover an entire tooth surface and can be re- 
moved only by mechanical means. 

Calculus. Dental calculus is a chalky or dark de- 
posit attached to the tooth structure. It is essentially 
microbial plaque that has undergone mineralization 
over time. Calculus can be found on tooth structure 
in a supragingival and/or a subgingival location. 

Acquired Pellicle. Pellicle is a thin, brown or 
gray film of salivary proteins that develops on teeth 
after they have been cleaned. It frequently forms 
the interface between the tooth surface and dental 
deposits. 

Materia alba. Materia alba is a white coating 
composed of microorganisms, dead epithelial cells, 
and leukocytes that adheres loosely to the tooth. It 
can be removed from the tooth surface by water 
spray or by rinsing. 

Structure of the Dental Plaque. Dental plaque 
consists mainly of microorganisms, scattered leuko- 
cytes, enzymes, food debris, epithelial cells, and 
macrophages in an intracellular matrix. Bacteria 
make up 70% of the solid portion of the mass. The 
remainder is an intracellular matrix consisting of 
carbohydrates, proteins, and calcium and phos- 
phate ions . 

As the plaque mass increases and matures, the 
flora progresses apically from a supragingival posi- 
tion, facilitated by the presence of gingival crevicular 
fluid. The flora also changes from a predominantly 
gram-positive, aerobic, and facultatively anaerobic 
population of coccoid morphology to a mix relatively 
high in gram-negative, anaerobic, and rodlike or fila- 
mentous organisms, along with increasing numbers 
of spirochetes. Evidences indicates that an in- 
crease in gram-negative organisms leads to an in- 
crease in disease activity within the periodontium 
and causes both direct and indirect tissue damage. 

As the plaque colony matures and increases its 
mineral content, calculus forms within the plaque 
mass. Although gingival inflammation is often most 
severe in areas where calculus is present, the calcu- 
lus itself is not the most significant source of in- 
flammation; rather, it provides a nidus for plaque 
accumulation and retains the plaque in proximity to 
the gingiva. Dental plaque is the etiologic agent of 
the inflammation. 2o 

PATHOGENESIS 

The pathogenesis or sequence of events in the devel- 
opment of a gingivitis-periodontitis lesion is very 
complex. It involves not only local phenomena in the 
gingiva, PDL, tooth surface, and alveolar bone but 



Chapter 5 Periodontal Considerations 



■ 



also a number of complex host response mechanisms 
modified by the bacterial infection and behavioral 
factors.21 Implicated in the pathogenic mechanism 
are phagocytic cells, the lymphoid system, antibodies 
and immune complexes, complement and clotting 
cascades, immune reactions, and the microcircula- 
tion. Detailed descriptions of host response in the 
gingivitis-periodontitis lesion can be obtained by re- 
ferring to standard periodontal texts . 

The chronic plaque-induced lesion has been in- 
vestigated- ^^ in great detail clinically, histopatho- 
logically, and ultrastructurally, and the model of 
disease activity has remained consistent over time. 
From these analyses, an indistinct division into ini- 
tial, early, established, and advanced stages has 
been put forth. The salient features and approxi- 
mate time frame for each stage are presented here. 

Initial Lesion. The initial lesion (Fig. 5-5) is lo- 
cahzed in the region of the gingival sulcus and is ev- 
ident after approximately 2 to 4 days of undisturbed 
plaque accumulation from a baseline of gingival 
health. The vessels of the gingiva become enlarged, 
and vasculitis occurs, allowing a fluid exudate of 
polymorphonuclear leukocytes to form in the sul- 
cus. Collagen is lost perivascularly, and the resul- 
tant space is filled with proteins and inflammatory 
cells. The most coronal portion of the junctional ep- 
ithelium becomes altered. 

Early Lesion. Although there is no distinct di- 
vision between the stages of lesion formation, the 
early lesion (Fig. 5-6) generally appears within 4 to 
7 days of plaque accumulation. This stage of devel- 



opment exhibits further loss of collagen from the 
marginal gingiva. In addition, an increase in gingi- 
val sulcular fluid flow occurs with increased in- 
flammatory cells and the accumulation of lymphoid 
cells subjacent to the junctional epithelium. The 
basal cells of the junctional epithelium begin to pro- 
liferate, and significant alterations are seen in the 
connective tissue fibroblasts. 

Established Lesion. Within 7 to 21 days the le- 
sion enters the established stage (Fig. 5-7). It is still 




Lymphocytes 



Neutrophils 



Fig. 5-6. Early lesion of gingivitis-periodontitis. The pre- 
dominant inflammatory cells are lymphocytes subjacent to 
the junctional epithelium. The epithelium is beginning to 
proliferate into rete ridges. 

(Redrawn from Schluger S et al: Periodontal disease, ed2, 
Philadelphia, 1990, Lea & Febiger.) 




Neutrophil 

Lymphocyte 

Vesse! 
Plasma celJ 



Fig. 5-5. Initial lesion of gingivitis-periodontitis. There is 
a predominance of polymorphonuclear leukocytes in the 
beginning stages of inflammation. 

(Redrawn from Schluger S et al: Periodontal disease, ed2, 
Philadelphia, 1990, Lea & Febiger) 




Plasma cells 



Neutrophils 



Fig. 5-7. EstabUshed lesion of gingivitis-periodontitis. 
The junctional epithelium is converted into pocket epithe- 
lium. Pocket formation may begin. The predominant in- 
flammatory cells are plasma cells. 

(Redrawn from Schluger S et al: Periodontal disease, ed2, 
Philadelphia, 1990, Lea & Febiger) 



■ 



Section 1 Planning and Preparation 




Fig. 5-8. Gingivitis. The interproximal gingiva is bul- 
bous and inflamed. Note the erythematous and edematous 
tissue extending onto the labial portions of the lateral 
incisors. 




Neutrophils 
Plasma cells 
Lymphocytes 



Fig. 5-9. Advanced lesion of gingivitis-periodontitis. 
Pocket formation has begun, with a loss of connective tis- 
sue attachment apical to the CEJ. Bone is converted into fi- 
brous connective tissue and is subsequently lost. The pre- 
dominant inflammatory cells are plasma cells, and there are 
scattered lymphocytes present. 

(Redrawn from SchlugerS et al: Periodontal disease, edl, 
Philadelphia, 1990, Lea & Febiger.) 



located at the apical portion of the gingival sulcus, 
and the inflammation is centered in a relatively 
small area. There is continuing loss of connective 
tissue, with persistence of the features of the early 
lesion. This stage exhibits a predominance of 
plasma cells, the presence of immunoglobulins in 
the connective tissue, and a proHferation of the func- 
tional epithelium (Fig. 5-8). Pocket formation, how- 
ever, does not necessarily occur. 

Advanced Lesion. It is difficuh to pinpoint the 
time at which the established lesion of gingivitis re- 
sults in a loss of connective tissue attachment to the 
tooth structure and becomes an advanced lesion or 
overt periodontitis (Fig. 5-9). Upon conversion to 
the advanced stage, the features of an established 
lesion persist. The connective tissue continues to 




Fig. 5-10. Periodontitis. Plaque and calculus accumula- 
tion has resulted in a loss of connective tissue attachment 
apical to the CEJ. 



lose collagen content, and fibroblasts are further al- 
tered. Periodontal pockets are formed, with in- 
creased probing depths, and the lesion extends into 
alveolar bone. The bone marrow converts to fibrous 
connective tissue, with a significant loss of connec- 
tive tissue attachment to the root of the tooth. This 
is accompanied by the manifestations of im- 
munopathologic tissue reactions and inflammatory 
responses in the gingiva. 

Periodontitis. When a loss of connective tissue 
attachment occurs, the lesion transforms from gin- 
givitis into periodontitis (Fig. 5-10), a disease that may 
be characterized by altemating periods of quiescence 
and exacerbation. The extent to which the lesion pro- 
gresses before it is treated will determine the amount 
of bone and connective tissue attachment loss that oc- 
curs. It will subsequently affect the prognosis of the 
tooth with regard to restorative demands. 

^ EXAMINATION, DIAGNOSIS, 
AND TREATMENT PLANNING 

Before treatment is rendered, all facts and findings 
related to the patient's disease state should be 
recorded.','," These data can then be used to formu- 
late a precise working blueprint for the proposed 
treatment. The diagnosis and treatment-planning 
stages should be completed before therapy is 
initiated. In general practice, the data collection, 
diagnosis, and treatment-planning for a patient's 
restorative needs are accomplished at approxi- 
mately the same time. 

The treatment plan should be concise, logical, 
and rational- a realistic approach to therapy. It 
should not be a rigid or inflexible sequence of 
events, because often it will need to be amended as 
new information or changing circumstances dictate. 
The timing and sequencing of treatment are impor- 



Chapter 5 Periodontal Considerations 



I 



tant to correcting the patient's dental problems as 
efficiently as possible. 

The following is a viable working model for peri- 
odontal treatment: 



INITIAL THERAPY 

Control of microbial plaque 

Toothb rushing 

Flossing 

Other aids 
Scaling and polishing 
Correction of defective and/or 
overhanging restorations 
Root planing 
Strategic tooth removal 
Stabilization of mobile teeth 
Minor tooth movement 

EVALUATION OF INITIAL THERAPY 
SURGICAL THERAPY 

Soft tissue procedures 

Gingivectomy 

Open debridement 

Mucosal repair (see Chapter 6) 
Hard tissue procedures 

Bone induction 

Osseous resection 
Treatment of furcation involvements 

Odontoplasty -osteoplasty 

Root amputation 

Hemisection 

Provisionalization 

Restoration 

EVALUATION OF SURGICAL THERAPY 

GUIDED TISSUE REGENERATION 

(HARD AND SOFT TISSUE PROCEDURES) 

Technique 
Restoration 

MAINTENANCE 
PROGNOSIS 

INITIAL THERAPY 

Initial therapy consists of all treatment carried out 
in advance of evaluation for the surgical phases of 
periodontal therapy. A number of procedures in 
each patient's treatment regimen may be accom- 
plished before more definitive or invasive ap- 
proaches are undertaken. 

Control of Microbial Plaque. The most critical 
aspect of periodontal therapy is the control of mi- 
crobial flora in the sulcular area. If the patient does 
not maintain excellent oral hygiene and thereby the 
optimum condition of soft and hard tissues, subse- 




Fig. 5-11. Bass sulcular method of toothbrushing. 



quent periodontal and restorative treatments will be 
jeopardized. 

Bacterial plaque occurs on all surfaces of the teeth 
but is especially prevalent on the gingival third ^^ It 
is strongly adherent to the tooth structure, which 
means that it is not removed by the chewing of fi- 
brous foods . 26 The prevention of plaque accumula- 
tion, by either mechanical or chemical means, is crit- 
ical to the prevention of hard and soft tissue 
pathosis. Although there are chemical means for re- 
moving plaque accumulation, only mechanical 
methods will be considered in this text. For excel- 
lent reviews of the subject of chemical plaque re- 
moval, refer to standard periodontal texts. 

Toothbrushing. Plaque removal is accom- 
plished with a toothbrush and other orophysiother- 
apy aids. Many types of toothbrushes can be used 
and are classified according to their size, shape, 
length, bristle arrangement, and whether they are 
manually or electrically powered. Reviews of the 
many types of brushes and alternate techniques can 
be reviewed in standard periodontal textbooks. 
The soft-bristle brush is particularly effective for 
cleaning in the gingival sulci and at buccal and lin- 
gual surfaces of interproximal areas without 
causing gingival damage and tooth abrasion that 
can result from a hard-bristle brush. ^^ 

Technique. In toothbrushing, effective placement 
of the bristles is more important than the amount of 
energy expended. The Bass sulcular method of 
brushing (Fig. 5-1 1) is preferred for most fixed 



I 



Section 1 Planning and Preparation 



prosthodontics patients because it cleans the sulci, 
where the margins of restorations are often placed. 
The bristles are placed in the sulci at an angle of 
approximately 45 degrees to the tooth surface, di- 
rected gingivally, and moved back and forth with 
short scrubbing motions under light pressure. The 
brush is applied in a similar manner throughout the 
mouth on all buccal and lingual or palatal surfaces 
of the teeth. In the anterior area, where interproxi- 
mal spaces are small and where it may seem impos- 
sible to place the brush horizontally against the gin- 
giva, the brush can be turned vertically for better 
access. After the sulcular areas have been cleansed, 
the occlusal surfaces are brushed, as is the dorsal 
surface of the tongue. For excellent descriptions and 
illustrations of toothbrush placement, refer to stan- 
dard periodontal texts. 5-7 

Flossing. Interproximal plaque can be con- 
trolled with dental floss. 31 Both waxed and un- 
waxed types will clean proximal surfaces, but the 
unwaxed floss has several advantages 32 

1. It is smaller in diameter and thus more easily 
passed through interproximal contact areas. 



2. It flattens out under tension, and thus each 
separate thread effectively covers a larger 
surface area. 

3. It makes a squeaking noise when applied to a 
clean tooth surface, which can be used as a 
guide to effective performance. 

Technique. A generous length of floss is cut and 
wrapped around the middle fingers of each hand. 
The forefingers and thumbs are used for placement 
(Fig. 5-12). The floss is slipped past the contact area to 
the base of the sulcus and is moved up and down on 
each proximal tooth surface until both surfaces are 
free of plaque. The floss is then removed and inserted 
in the next proximal area, systematically progressing 
until all the proximal surfaces have been cleaned. 

Other Aids. Plaque may also be controlled ef- 
fectively by orophysiotherapy aids such as dental 
tape, yam, rubber and wooden tips, toothpicks, in- 
terdental stimulators, interproximal brushes, and 
electric toothbrushes. 

When plaque is removed around a fixed partial 
denture or a restoration involving splinted teeth, a 
floss threader may be needed. Alternatively, special 




C D E 

Fig. 5-12. Proper use of dental floss. A, Forefinger grip for positioning. B, Thumb grip for position- 
ing. C, The floss is placed apical to the contact area and is gently worked to the base of the sulcus. 
D, After cleaning the mesial portion of the proximal sulcus, the floss is moved coronally and placed at 
the distal portion of the sulcus. E, Cleaning the distal portion of the proximal sulcus (i.e., mesial of the 
adjacent tooth). 



Chapter 5 Periodontal Considerations 



I 



lengths of floss with stiffened ends are available and 
have been shown to be quite effective. 

Disclosing agents may be used to provide better vi- 
sualization of areas where plaque control is difficult 
or deficient. Erythrosin dye in tablet or liquid form 
stains plaque and is readily observable. Ultraviolet 
light has been used in combination with fluorescein 
dye to reveal plaque deposits, bypassing the undesir- 
able red stain that remains after erythrosin use. 

All the previously mentioned items are useful in 
removing and controlling inflammation-inducing 
microbial plaque. However, the most important as- 
pect of plaque control is patient motivation. Without 
motivation, all orophysiotherapy aids and the 
knowledge to apply them are useless. 

Scaling and Polishing. Removal of supragingi- 
val calculus (scaling) and polishing of the coronal 
portion of the tooth are the first definitive steps in 
debridement of the teeth. Scaling consists of the re- 
moval of deposits and accretions from the crowns of 
teeth and from tooth surfaces slightly subgingival. 
This is accomphshed with the use of sharp scalers or 
curettes. The gingiva responds to this removal of 
supragingival and slightly subgingival calculus with 
a decrease in inflammation and bleeding. Thus the 
patient is able to observe the first signs of therapeu- 
tic gain, especially when part or half of the mouth is 
instrumented at one appointment, and the remain- 
der is done after a short amount of time has elapsed. 

Correction of Defective and/or Overhanging 
Restorations. Overhanging restorations, open in- 
terproximal contacts, and areas of food impaction 
contribute to local irritation of the gingiva and (of 
greater importance) impede proper plaque control. 
These deficiencies (Fig. 5-13) should be corrected 




Fig. 5-1 3. Overhanging splinted restoration connecting 
the mandibular right and left central incisors, with oblitera- 
tion of the interproximal space by the castings. The pa- 
tient's inabiUty to clean this area properly has resulted in 
iatrogenic loss of attachment. 



during the initial therapy phase of treatment by ei- 
ther replacement or reshaping and/or removal of 
the overhang (Fig. 5-14). Close cooperation and 
communication between the periodontist and the 
restorative dentist are essential during this treat- 
ment phase. 

Root Planing. Root planing (Fig. 5-15) is the 
process of debriding the root surface with a curette. 
It is a more deliberate and more delicately executed 
procedure than scaling and requires the adminis- 
tration of a local anesthetic in most instances. At 




Fig. 5-14. Recontouring of the interproximal space of 
the castings seen in Fig. 5-13 allows the patient to clean the 
area. Note the excellent gingival health between the central 
incisors as a result of good oral hygiene techniques. 



Oral hygiene mstruction and 
calculus removal are pre- 
requisite to fixed prosthodon- 
tic treatment 





Fig. 5-1 5. Root planing. A, Curette placed in the sulcus 
to address calculus. B, The curette, initially placed apical to 
the calculus, moves coronally to dislodge the calculus. 
C, Accretions removed and the root planed to a smooth fin- 
ish. CU, Curette; CA, calculus; S, sulcus; R, root surface. 

(Redrawn from Carranza FA Jr: Glickman's clinical periodon- 
tology, ed 7, Philadelphia, 1990, WB Saunders.) 



I 



Sertion 1 Planning and Preparation 



present it constitutes the primary mode of initial 
therapy in periodontiss, and evidence suggests that 
disease progression will continue without root plan- 
ing, even with effective oral hygiene 33 

The curette is a spoon- shaped instrument well 
suited to cleaning and smoothing root surfaces. It is 
applied apically on the root with respect to the ac- 
cretion and is moved coronally to lift deposits off 
the root surface and to plane it to a glasslike 
smoothness. As the patient's plaque-control tech- 
niques improve, the changes observed when root 
planing is completed may necessitate changing or 
modifying the treatment plan, and further therapy 
may not be indicated. 

Root planing and the incidental curettage of soft 
tissue that accompanies it may be an end point of 
active periodontal therapy. In many cases the com- 
bination of root planing and improved oral hygiene 
on the part of the patient leads to manageable prob- 
ing depths, and no further treatment is necessary. 
For this reason the initial therapy requires careful 
evaluation. 

Strategic Tooth Removal. An important part of 
treatment sequencing is the elimination of teeth that 
are hopelessly involved periodontally or are nonre- 
storable. Although no hard-and-fast rules exist re- 
garding the timing of such extractions, removing 
teeth early in therapy is often more advantageous, 
when the patient has recently been informed of the 
prognosis and is prepared for treatment. 

Extractions can be accomplished during initial 
therapy when the quadrant being instrumented is 
anesthetized. The operator can make an excellent 
determination of questionable teeth at this time by 
"sounding" the periodontium and can inform the 
patient of the verdict immediately. The patient is 
thus prepared psychologically (and also pharmaco- 
logically) for the removal. Teeth can also be re- 
moved during periodontal surgery, when the same 
conditions exist. 

Early extraction of teeth and/or roots will allow 
the socket areas to heal and can provide better access 
for plaque control of adjacent tooth surfaces. A transi- 
tional or provisional RPD or FPD can also be fabri- 
cated and will stabihze the arch and potentially main- 
tain or improve occlusion, function, and esthetics. 

Stabilization of Mobile Teeth. Tooth mobility 
occurs when a tooth is subjected to excessive forces, 
especially when bony support is lacking. It is not 
necessarily a sign of disease, because it may be a 
normal response to abnormal forces, and it does not 
always need corrective treatment. However, it is 
sometimes a source of discomfort to the patient, and 



in these cases it should be treated by reduction of 
the abnormal forces after occlusal evaluation. De- 
pending on the patient's need, the teeth may also be 
treated by splinting with provisional restorations 
(see Chapter 15) or an acid-etch resin technique (see 
Chapter 26) in conjunction with occlusal adjustment 
(see Chapter 6). Such restorations should be care- 
fully designed so they do not impede plaque control 
or future periodontal treatment. Close communica- 
tion between the periodontist and the restorative 
dentist is critical in this phase of treatment. 

Minor Tooth Movement. Orthodontics can be 
of major benefit to periodontal therapy. Malposed 
teeth may be realigned to make them more receptive 
to periodontal treatment and to improve the efficacy 
of plaque-control measures. As seen in Chapter 6, 
restorative procedures can also be aided by minor 
tooth movement. Thus, for the best treatment of a 
patient with complex dental problems, good com- 
munication among consulting dentists is essential. 

EVALUATION OF INITIAL THERAPY 

The periodontium recovering from active disease 
should be regularly reexamined and reevaluated to 
determine the efficacy of treatment. Soft tissue re- 
sponses to the initial therapy are observed along 
with the patient's motivation and ability to main- 
tain a relatively inflammation- free state. Probing 
depths should be recorded again, and the location 
of the mucogingival junction noted in relation to the 
teeth. Changes must be assessed in regard to the ne- 
cessity of further periodontal treatment. 

Reevaluation gives the practitioner a firmer grasp 
on the progress of treatment, and if necessary, it al- 
lows revision of the initial treatment plan. At this 
time, the gingiva is healthier, probing depths may 
have decreased because of better plaque control and 
root planing, and an improved working knowledge 
of the patient's abilities and desires should exist. 
The combination of these factors facilitates deci- 
sions regarding further treatment of the periodon- 
tium and allows a more informed prognosis. 

SURGICAL THERAPY 

There are a number of surgical procedures for the 
improvement of plaque removal aimed primarily at 
reducing or eliminating probing depths. Accurately 
diagnosing and choosing the most appropriate sur- 
gical regimen is crucial for maximum results. 

Soft Tissue Procedures 

Gingivectomy. Gingivectomy is the removal of 
diseased or hypertrophied gingiva. Introduced by 
G.V. Black,^^^ it was the first periodontal surgical 



Chapter 5 Periodontal Considerations 



I 



approach to gain widespread acceptance. Gingivec- 
tomy is essentially the resection of keratinized gin- 
giva only, and it may be applied to the treatment of 
suprabony pockets'36 and to fibrous or enlarged gin- 
giva, particularly when they result from diphenyl- 
hydantoin (Dilantin) therapy 37 (see Fig 1-4). How- 
ever, it is unsuitable for the treatment of infrabony 
defects. 

Technique. The surgical technique consists of es- 
tablishing bleeding points (Fig. 5-16) at the base of 
the gingival sulcus with a pocket marker or peri- 
odontal probe to serve as a guide for the gingival 
excision. The initial incision (Fig. 5-17) is made to 
these points in a beveled fashion with firm, contin- 
uous strokes from the gingivectomy knife. The in- 
terproximal tissue is freed by sharp excision and is 
removed from the site. The resulting ledge of tissue 
at the buccal and lingual or palatal terminations of 
the incision (Fig. 5-18) is then smoothed with the 




Fig. 5-1 6. Demarcation of pocket depth before the initial 
incision of a gingivectomy. 






^^W|HHHI|[fftl'^£^g»»> 


1 


-J^^^^^^B 


\ 


1^ 



Fig. 5-1 7. Initial incision for the gingivectomy. 




knife or a rotary instrument to a margin continuous 
with the remaining tissue. 

After vigorous debridement of the newly accessi- 
ble tooth surfaces, a surgical dressing is applied for 
protection and hemostasis; it remains in place for 7 
to 10 days. When it is removed, oral hygiene proce- 
dures are immediately resumed (Fig. 5-19). 

Contraindications. The major contraindication to 
gingivectomy-gingivoplasty is the absence of at- 
tached keratinized tissue. The procedure should be 
confined to areas of keratinized tissue to prevent 
leaving gingival margins that consist of alveolar 
mucosa (which is ill-suited to resisting the trauma 
of restorative procedures and mastication). 

Open Debridement (Modified Widman Proce- 
dure). Open debridement or curettage is a surgi- 
cal procedure designed to gain better access to root 
surfaces for complete debridement and root plan- 
ing. The modified Widman approach 38 has been ad- 
vocated in recent years, because it allows good soft 
tissue flap control, minimum surgical trauma, and 
good postoperative integrity without excessive loss 
of osseous tissue or connective tissue attachment. 

Technique. A sulcular or minimal internal bevel 
incision (Fig. 5-20) is made on the buccal or the lin- 
gual surfaces of the mandibular teeth. Next, a scal- 
loped internal bevel incision is made on the palatal 
surfaces of maxillary teeth. The palatal flap is then 
thinned and the underlying connective tissue re- 
moved. The resulting flaps are reflected minimally 
yet sufficiently to allow access for complete de- 
bridement of the root surfaces and degranulation of 
any osseous lesions in the field. No osseous resec- 
tion is accomplished, except where necessary for 
proper flap placement. The flaps are then carefully 
coapted and sutured to promote healing by primary 
intention (Fig. 5-21). 

Mucosal Repair. Mucosal reparative surgery 
is used to increase the width of the band of kera- 
tinized gingiva. It is particularly useful where 




"1 




Fig. 5-18. Final gingival contours after removal of the 
coronal tissue and beveling of the incised area. 



Fig. 5-19. Result of the gingivectomy, 6 months after 
surgery. Note the excellent gingival health and contours. 



I 



Section 1 Planning and Preparation 

I 





Fig. 5- Internal bevel incision. A, Ending on the bone, to allow reflection of the flap. B, Flap 

reflected. The supracrestal connective tissue and epithelium are to be removed. E, Enamel; S, sulcus; 
P, supracrestal periodontium; R, root. 
(Redrawn from Carranza FA fr: Glickman's clinical periodontology, ed 7, Philadelphia, 1990, WB Saunders.) 



CD 



f,G 




H 



A, Initial thinning incision on the buccal for open debridement. B, Lingual flap thinned. 
C, Roots planed to remove subgingival accretions. D, Roots debrided and planed. E and F, Flaps coapted 
and sutured. G and H, The completed restoration, with a healthy periodontium. 



complete-coverage restorations are planned (see 
Chapter 6 for a more detailed discussion). 

Hard Tissue Procedures 

Hard tissue therapy is aimed at modifying the 
topography of areas where plaque control is diffi- 
cult or impossible. Two examples are obvious: 



1. 



2. 



In areas where an irregular pattern of bone 
loss has led to intrabony pockets. 
Around root furcations (hard tissue proce- 
dures may include techniques for the induc- 
tion of new bone formation, for the judicious 
removal of bone by surgery, and for tooth 
modification or root resection.) 



Chapter 5 Periodontal Considerations 



I 



Bone Induction. Intrabony lesions (Fig. 5-22) 
are categorized as one-walled, two-walled, or three- 
walled, depending on the remaining osseous topog- 
raphy. The three- walled defect responds best to in- 
ductive or de granulation procedures, with resulting 
new attachment and resolution of all or part of the le- 
sion. The one-walled and two-walled (crater) defects 
respond better to pocket elimination procedures ^^ 

Many materials have been used to fill osseous 
defects: ceramic; ° sclera, 1 cartilage m bone chips ,43 
cementum and dentin ,44 osseous coagulum,45 freeze- 
driedbone,46 iliac crest marrow,' hydroxylap- 
atite,49 tricalcium phosphate,'° and bioactive glass 
materials. 51,12 Results have been mixed, and no cur- 
rently available alloplastic grafting material is 
clearly superior to any other in the regeneration of 
periodontal defects. 

Technique. After the flaps have been reflected and 
the lesion thoroughly degranulated, the grafting 
material is packed firmly into the lesion until it is 
slightly overfilled. The flaps are then coapted, and 
interrupted sutures are placed (Fig. 5-23). A surgical 
dressing is applied and removed after 7 to 10 days. 

Osseous Resection with Apically Positioned 
Flaps. Chronic inflammatory periodontitis results 
in the loss of osseous tissue, destruction of osseous 
architecture, and creation of an intrabony lesion. 
The osseous tissue has no predictable or simple pat- 
tern of loss; the resorption may take the form of 
craters, hemiseptal defects, or well-like (troughlike) 
shapes. Craters in the interproximal areas (Fig. 5-24) 
are the most common type of lesion. 

The objective of osseous resection is to shape the 
bone to form even contours. This is accomplished 
by leveling interproximal lesions, reducing osseous 



recontour lesions that are too wide and/or shallow 
for predictable repair or bony fill, thinning bony 
ledges, and eliminating or ramping crater defects. 
The result is intended to be a sound osseous base for 
gingival attachment and the elimination of pockets 
and excessive sulcular depth. Long-term studies 
have shown that although osseous resection 
surgery results in attachment loss and gingival re- 
cession, it is the most effective therapy for decreas- 
ing pocket depth, which can subsequently be main- 
tained by the patient. 

Technique. Beforc reflection of the flaps, the os- 
seous topography of the lesion is assessed. After the 
area to be treated has been anesthetized, a peri- 
odontal probe is inserted into the pocket and forced 
through the epithelial attachment and connective 
tissue to the osseous crest. Multiple probings are 
made and the surface morphology is observed. This 
"sounding" of the bone provides a reasonable rep- 
resentation of the width and depth of the lesion and 
is helpful in designing the incision. 

Inverse bevel incisions are made on the buccal 
and lingual or palatal surfaces, and full-thickness 
mucoperiosteal flaps are reflected to expose the os- 
seous tissue. After the flaps are thinned and the le- 
sions are thoroughly degranulated, the roots of the 
teeth are planed vigorously. Osseous resection is 
then accomplished by the combination of rotary in- 
strumentation with carbide and/or diamond burs, 
chisels, and bone files. When osteoplasty of the in- 
terproximal sluiceways, furcation areas, and buccal 
and lingual bone is completed, the flaps are posi- 
tioned at the crest of the bone in an apical position 
on the tooth. Surgical dressings are applied, and in 
7 to 10 days, the patient is seen again for suture re- 
moval and dressing removal or change. 






Fig. 5-22. Osseous defects. A, Three walls of bone present: at the lingual (1), distal (2), and buccal (3). 
B, Two walls of bone (1 and 2) in the coronal portion of the defect and three walls (1,2, and 3) in the api- 
cal portion. C, The two coronal walls have been removed and the buccal surface of the bone recon- 
toured, leaving the apical three-walled defect to fill with bone after degranulation. 

(Redrawn from Carranza FA fr: Glickman's clinical periodontology, ed 7, Philadelphia, 1990, WB Saunders.) 



■ 



Section 1 Planning and Preparation 

A B 




Fig. 5-23. a, Degranulation of a mesial defect on the mandibular right canine. This is a three-walled 
defect, with approximately 9 mm of intrabony lysis. B, The defect has been filled (sHghtly overfilled) 
with autogenous iliac crest marrow coagulum. C, Sulcular depth of approximately 3 mm 4 months after 
surgery. D, Osseous fill at reentry 1 year after surgery. Note the rim of bone at the margin of a previ- 
ously existing defect (arrow). E, 1 year after surgery there is a near- total fill of the defect. The rim of bone 
demarcates the margin of the previous intrabony lesion. F, Result of osseous grafting at the mesial of the 
canine 15 months after surgery. The gingival health and contours are excellent. Note the acrylic resin 
provisional restoration in place before the final restoration. 




Fig. 5-24. a, Osseous ledge and a crater defect. B, Osseous recontouring. C, Final restoration 
3 months after apical positioning of the flap. 



Postsurgical Healing. Postsurgically, the healing 
of the periodontium must be considered before any 
restorative procedures are performed. Initial con- 
nective tissue and epithelial healing is complete at 4 
to 6 weeks. Final tissue maturation and sulcus re- 
formation, however, may not be complete until 6 
months to 1 year after surgery. 

If the margins of the restorations are to be placed in- 
trasulcularly (subgingivally) or at the gingival crest or 
if gingival displacement procedures are to be used in 
making the impression, waiting as long as possible 



postsurgically before attempting these procedures is 
recommended. If the restorative margins are to be 
placed at a suprasulcular (supragingival) position 
(which may not necessitate the use of a gingival dis- 
placement cord), these restorations may be started 
when the gingiva exhibits initial reepithelialization and 
a return to cHnical health (approximately 4 to 6 weeks). 

Treatment of Furcation Involvement 

Diagnosis and treatment of furcation involvement 
of multirooted teeth is one of the more difficult 



Chapter ^ Pmodontal Considemtions 



I 





Normal 



Fig. 5-25. Normal relationship of the CEJ and the 

osseous crest. 

(FromBaimaRF: J Prosthet Dent 56:138, 1986.) 



problems encountered in the periodontal-restora- 
tive dentistry continuum. Famiharity with the fur- 
cation's anatomic and morphologic variations is es- 
sential when formulating a treatment plan and 
prognosis for multirooted teeth. 

Classification of Involvements. Furcation in- 
volvements can be classified as Class (or Grade) I,II, 
III, and IV Because these classifications are arbi- 
trary, however, the reader should refer to periodon- 
tal textbooks and other readings for further de- 
tail and clarification. 

The normal position of the osseous crest (Fig. 5-25) 
is approximately 1.5 mm apical to the cementoenamel 
junction (CEJ) in a young, healthy adult. If vertical 
loss of periodontal support is less than 3 mm apical to 
the CEJ, this is considered to be Class I involvement 
(Fig. 5-26, A). There is no gross or radiographic evi- 
dence of bone loss. Clinically the furca can be probed 
up to 1 mm horizontally. If vertical loss is greater than 
3 mm but the total horizontal width of the furcation is 
not involved. Class II involvement (Fig. 5-26, B) exists. 
A portion of the bone and periodontium remains in- 
tact, but osseous loss is evident on radiographs. The 
furca is penetrable more than 1 nrni horizontally but 
does not extend through- and-through. 

A horizontal through- and-through lesion that is 
occluded by gingiva but allows passage of an in- 
strument from the buccal, lingual, or palatal surface 
is defined as a Class III involvement (Fig. 5-26, C . 
The degree of osseous loss is grossly evident on ra- 
diographs. A horizontal through- and-through le- 
sion that is not occluded by gingiva is defined as a 
Class IV involvement (Fig. 5-26, D). 

Review of Root Anatomy. The discussion of 
root anatomy is logically divided into maxillary and 
mandibular teeth. 

Most maxillary molars have three roots - 
mesiobuccal, distobuccal, and palatal- although 






II 





Fig. 5-26. Furcation involvements. A, Class 1. B, Class 11. 

C, Class 111. D, Class IV. 

(From BaimaRF: J Prosthet Dent 56:138, 1986.) 



there may be variations, such as fused roots or 
fewer roots, particularly with second and third 
molars. The mesiobuccal root of most maxillary mo- 
lars, especially the first molar, is usually biconcave 
and curves to the distal. The distobuccal root also is 
biconcave and somewhat less curved. The palatal 
root is wide buccolingually and mesiodistally and 
palatally diverges from the crown of the tooth. This 



■ 



Section 1 Planning and Preparation 



configuration is unique to human dentition and 
may pose special problems when preparing, restor- 
ing, and designing restorations. The distobuccal 
and palatal roots tend to be in the same plane dis- 
tally, and the distal furcation is more apical on the 
tooth than the mesial furcation. In spite of this 
anatomy, the distal furca is more often involved in 
periodontal lesions than the mesial furca. From the 
apical perspective, a groove tends to unite the buc- 
cal and mesiopalatal openings of the bifurcation 
and can be probed when there is furca involvement. 
Most mandibular molars have two roots-mesial 
and distal- although, as with maxillary molars, 
there may be variations. The mesial root is flattened 
buccolingually, with concave surfaces on each prox- 
imal side. It curves distally, especially in first mo- 
lars. The distal root is wider buccolingually than the 
mesial root and is concave on its mesial side. Its 
apex is often curved distally with a flat or convex 
distal aspect. Both root surfaces of mandibular mo- 
lars facing the furca are concave, resulting in an os- 
seous chamber that is wider mesiodistally than ei- 
ther the buccal or the lingual furcation opening. The 



roof of the furcation is difficult to maintain because 
of mesiodistal bifurcation ridges. 

NOTE: Maxillary and mandibular second and 
third molars often have more apically placed furcas 
than first molars and often exhibit fused roots with 
little or no furcation . 

Maxillary premolars, particularly first premolars 
and (at times) mandibular premolars, also have fur- 
cations. However, because they are rarely amenable 
to treatment by odontoplasty-osteoplasty or root 
amputation procedures,' they will not be discussed 
here. Students should refer to oral anatomy and 
morphology textbooks'", " for further clarification 
and study of molar root anatomy. 

Odontoplasty-osteoplasty. Lesser degrees of 
furcation involvement can often be controlled by 
root planing and scaling, adequate oral hygiene, 
and/or gingivectomy-gingivoplasty However, when 
the involvement is more extensive, recontouring of 
the tooth or bone may be necessary. 

Class I and incipient Class II lesions (Fig. 5-27) 
can be treated by reflecting the soft tissue in the fur- 




Fig. 5-27. Treatment of a Class 1 1 furcation lesion. A, The periodontal probe discloses approximately 
3 mm of horizontal involvement. B, The lesion reduced to Class I by odontoplasty-osteoplasty. Note the 
contours of the tooth at the coronal portion of the buccal furcation (arrow). C, Preparations for a fixed 
partial denture to be placed in the right mandibular quadrant. Note the figure- 8 shape of the molar 
preparation. D, Final restoration of the molar. There is excellent gingival health in the furcation area (ar- 
row). E, Restoration of the quadrant. Note the slight contact of pontic on ridge and the open embrasures 
for access by oral hygiene instruments. 
(Courtesy Dr. H.J. Gulbransen.) _ 



Chapter 5 Periodontal Considerations 



I 



cation area and recontouring both the tooth struc- 
ture and the supporting bone to improve access for 
cleaning. 4,57 Pocket elimination in this manner pro- 
vides the best results and the fairest prognosis. A 
minimal amount of tooth structure and bone is lost, 
and the patient can easily maintain it. 

Class II and Class III involvements can be treated 
by a procedure known as tunneling. ^^ The osseous 
structure is completely removed in the furcation, 
converting the lesion to a through- and-through de- 
fect. Teeth suitable for tunneling must have long, di- 
vergent roots, which will faciUtate penetration by an 
oral hygiene aid (e.g., a proximal brush or a pipe 
cleaner). Patient selection is particularly important, 
because oral hygiene and patient motivation are crit- 
ical. Failure to maintain the furcation in a relatively 
plaque-free state may lead to caries, which are often 
impossible to correct. The common location of acces- 
sory canals in the roof of the furca can also be a prob- 
lem. Because of irreversible pulp damage, endodon- 
tic treatment may be needed at a later date. 58. ^^ ^^ 
Root Amputation. In many patients. Class II 
and Class III furcation lesions are most effectively 
treated by root amputation (Fig. 5-28), which elimi- 
nates the furcation completely. The indications are 
as follows,'-63,65-67: 

1. Severe vertical bone loss involving one root 
of a mandibular molar or one or two roots of 
a maxillary molar 

Furcation involvement that is not treatable 
by odontoplasty-osteoplasty 
Vertically or horizontally fractured roots or 
teeth from trauma or endodontic procedures 
Unfavorable root proximity precluding 
treatment by conservative measures 
Severe caries 

Internal or external resorption 
Inability to treat one root canal successfully 
Severe dehiscence and sensitivity of a root 
that precludes grafting procedures 
Failure of an abutment in a long- span splint 
orFPD 



2. 

3. 

4. 

5. 
6. 

7. 



9. 



10. Strategic removal of a root to improve the 
prognosis of an adjacent tooth 

Certain roots will not be suitable for amputation. 
Individual considerations include the extent of fur- 
cation involvement, the anatomy and topography 
of the supporting bone, the anatomy of the root 
canal, and the periapical health of the tooth. The 
major contraindications to root resection are teeth 
exhibiting any of the following 63, 6t. 

1. Closely approximated or fused roots 

2. Significantly decreased general osseous sup- 
port or an increased crown/root ratio 

3. Remaining structure that will not provide ad- 
equate resistance against the forces of masti- 
cation 

4. Excessive loss of supporting root structure 

5. Inability to be treated endodontically 

6. Remaining structure that cannot be restored 
Before the gingiva is reflected, the furca is probed 

with a curved furcation instrument so that the pre- 
cise location of the bur cut can be determined (Fig. 
5-29). The cut is then made over the center of the 
furca but sHghtly toward the root to be removed. This 
will protect the residual root and/or tooth body. 
Whenever possible, the cut should be made before 
reflecting the flap so the field will be cleaner when 
the osseous tissue is exposed. When the cut is made 
into the root to be removed, the operator is able to in- 
spect the residual root and remaining furcation area. 
A lip is often created in the furcation area, however 
(Fig. 5-30), and after the root to be extracted has been 
delivered, the furcation lip is removed and the tooth 
is finally contoured and finished. Removing the lip 
from the root of the furca is crucial to the treatment's 
success. If this is not done, the osseous tissue will not 
be recontoured properly (Figs. 5-31 and 5-32), plaque 
control will be impaired, and, in effect, the furca will 
still be present .4,67,68 

There are few surgical problems with root resec- 
tion. The ones most frequently encountered are 
fracture of the root69 and loss of a root tip in the 



B 




Fig. 5-2.8. Types of root amputation. A, Mesiobuccal. 
B, Distobuccal. C, Palatal or mesiobuccal and distobuccal. 




Fig. 5-29. Mesiobuccal root amputation. A full-thickness 
flap has been reflected to reveal Class I buccal furcation in- 
volvement and a Class 1 1 lesion in the mesiopalatal furca. 



I 



Section 1 Planning and Preparation 




Fig. 5-30. The mesiobuccal root is sectioned at approxi- 
mately 45 degrees to the tooth trunk. The section has been 
made into the root that is to be removed, and the result is a 
lip at the buccal furca. 




Fig. 5-31 . Final osseous contours after removal of the 
mesiobuccal root and osteoplasty-ostectomy. The furcation 
lip has also been removed. 




Fig. 5-32. Mesiobuccal root amputation, 2 months after 
surgery. The remaining tooth structure is stabilized with a 
wire- and- acrylic resin provisional splint. 

maxillary sinus." , " Osseous anatomic features like a 
flat mandibular shelf and a flat palatal area can make 
access to the surgical site difficult and may complicate 
flap placement. Root proximity may complicate flap 
placement. Root proximity can pose a problem for 
separation and removal of the sectioned fragment 
from the surgical site. Mucogingival anatomy must be 
considered, because any flap procedure is contraindi- 
cated if there is a lack of keratinized attached gingiva. 

Hemisection. Heniisection means cutting 

a tooth in half. In the case of mandibular molars, 
hemisection is followed by removal and subsequent 




Fig. 5-33. Initial bur cut for hemisection and removal of 
the mesial root of a mandibular right first molar. The cut 
was made before reflection of the flap. 





tff 



Fig. 5-34. A, Removal of the mesial root of a mandibu- 
lar right first molar and final osseous contouring. B, Hemi- 
section and removal of the mesial root, 2 months after 
surgery. The remaining tooth structure has been stabilized 
with a wire -and- acrylic resin provisional restoration. 

restoration of one root or restoration of each half of 
the tooth. The latter procedure is sometimes called 
premolarization or bicuspidization.68 

The technical procedures of hemisection and root 
amputation are similar (Fig. 5-33). If one hemisected 
root is to be extracted, osteoplasty-osteoectomy and 
removal of the furcation lip are performed as previ- 
ously described (Fig. 5-34). If the roots are to be 
maintained and restored separately, the furca re- 
quires special attention for removal of furcation lips 
from each root. The individual roots may then be 
separated orthodontically, if necessary, to gain new 
interseptal osseous area .62- 

Provisionalization. Provisional stabilization 
is indicated in many cases of root resection to allow 
proper healing of the surgical site before definitive 
restorations are placed and to stabilize the remain- 
ing tooth structure against masticatory forces, 73 
(Fig. 5-35). 

Normally, an acrylic resin provisional restoration 
(Fig. 5-35, A) is provided (as described in Chapter 
15), although on occasion an existing restoration can 
be successfully modified as a provisional (Fig. 5-35, 
D). Acid-etch retained composite resin or amalgam 
with orthodontic wire (Fig. 5-35, B, C) can also be 
used on an interim basis to maintain space and sta- 
bilize remaining tooth structure. 



Chapter "> PenoHontnl ron<;irlpmtions; 



I 




Fig. 5-35. Provisional restorations. A, Acrylic resin with an overcontoured area corresponding to the 
mesial root of the mandibular right second molar. Ideal contouring of such a provisional would remove 
excess resin where the root had been amputated (arrow). B, Wire-and-acrylic resin splint stabilizing the 
mandibular right quadrant. C, Wire-and-amalgam splint. D, Existing restoration lined with acrylic resin 
(arrow). This Can serve adequately as a provisional restoration. 

(A courtesy Dr S.B. Ross; C courtesy Dr K.G. Palcanis; D courtesy Dr H.J. Gulbransen.) 



Restoration. Teeth with a resected root or roots 
may be restored in a variety of ways. ^^ ^^^^ They 

may be involved in a treatment plan as single units, 
as fixed or removable partial denture abutments, or 
as vertical stops for an overdenture. 

The most common types of restorations for teeth 
with resected roots involve: 

1. The remaining root restored as an individual 
tooth (Fig. 5-36) 

2. The tooth used as an abutment for a fixed or 
removable partial denture (Fig. 5-37) 

3. Premolarization-individual roots of a molar 
restored with premolar morphology ee (Fig. 
5-38) 

4. Minimum treatment-amalgam placed in the 
root(s) and the occlusion adjusted" 

EVALUATION OF SURGICAL THERAPY 

The prognosis for a tooth whose root(s) have been 
resected and/or amputated depends on many fac- 
tors. The manner in which the tooth is to be used in 
the restorative plan-as an abutment for a partial 
denture or as a single crown-has a bearing on 
prognosis,?, ^^ The amount of residual osseous struc- 

ture to support the remaining tooth also influences 
the outlook. Most important, however, are the moti- 



vation and oral hygiene of the patient. Long-term 
studies considering all of these factors have re- 
ported results ranging from 4%, to 38% loss of resid- 
ual roots with up to 53 years of postsurgical ser- 
vice 1 With careful diagnosis, treatment planning, 
and good surgical technique, the tooth with re- 
sected roots may have a favorable prognosis. Plaque 
control is critical. For this reason, the patient has the 
final word about whether the tooth will ultimately 
be lost or remain as a healthy functioning unit in the 
dentition. 

GUIDED TISSUE REGENERATION (HARD AND SOFT 
TISSUE PROCEDURES) 

It has long been a goal of periodontal therapists to 
replace lost connective tissue attachment and bone. 
As previously described, many materials have been 
used in the quest for reattachment to diseased root 
surfaces. In the recent past, regaining lost attach- 
ment with cells from the host has been successful. 
Through the use of physical barriers that prevent 
cells from the gingival connective tissue and api- 
cally migrating oral epithelium from contacting the 
root surface, space is created over the root surface, 
which allows selective repopulation of this space by 
cells from the residual periodontal ligament. These 



I 



Section 1 Planning and Preparation 




0,E 



CD 



Fig. 5-36. Mesial root of a mandibular left first molar prepared for a single crown restoration. 
A, Canals have been made parallel for a dowel and core. B, Casting with parallel dowels. C, Dowel and 
core restoration cemented and the root prepared for a single crown. D and E, Single nonsplinted restora- 
tion of the mesial root of a mandibular left first molar. 




Fig. 5-37. Distal root of a mandibular right first molar prepared for a dowel and core restoration. 
A, The root will be used as an abutment for a fixed partial denture. B and C, Dowel and core restoration 
of the root. D, Final restoration, with the root used as the distal abutment for a fixed partial denture. 
Note the excellent gingival health and contours. E, Final restoration of the mandibular right quadrant, 
lingual view. The point contact of the totally convex pontic and the wide embrasure spaces allow opti- 
mum oral hygiene and excellent gingival health. 



eM^-8(i)e^me the regenerated periodontal liga- 

Several types of barriers, 82,85 both resorbable and 
nonresorbable, as well as native periosteum 86 have 
been used to regenerate the periodontium about 
root surfaces,87 in furcations, and with dental im- 



plants. The most significant evidence has been 
attained by the use of a nonresorbable, polytetraflu- 
oroethylene (PTFE) barrier (Gore-Tex Periodontal 
Material). Although long-term, follow-up results 
are not conclusive, coronal movement of the con- 
nective tissue attachment has been impressive in 



A 



rhapter ^ Periorlontal ronsiHerations 

C .1 



I 




Fig. 5-38. Premolarization. Mesial and distal roots of a mandibular right first molar after hemisec- 
tion. A, A wire-and- aery lie resin provisional is in plaee. B, The mesial and distal roots have been pre- 
pared for a dowel and core. Each will be restored as an individual premolar. Note that the distal root has 
been moved (orthodontically) 4 mm to the distal before the restoration was fabricated to provide room 
in the newly created interproximal area for the dowel and core and crown restorations. C, The dowel 
and cores in place. Note the space between the roots created by the orthodontic movement. D, Dies with 
die relief placed and mounted on a suitable articulator for fabrication of the final restoration. E and F, Fi- 
nal result. The open interproximal areas and flat emergence profiles from the gingival area will permit 
optimum oral hygiene and assist in the preservation of gingival health. 



many clinical and laboratory investigations. Al- 
though guided tissue regeneration is a technique- 
sensitive mode of therapy and has yet to be viewed 
as widely successful, it may prove to be the most 
promising approach to regeneration. 

Technique (Fig. 5-39 and 5-40). Following diag- 
nosis of the lesion and any initial therapy deemed 
appropriate, full-thickness flaps are reflected in an 
attempt to maintain the maximum amount of tissue 
for coverage of the barrier. The lesion is completely 
debrided of granulation tissue, and the roots are 
planed thoroughly. 

The barrier is placed at the CEJ and secured with 
sutures placed in a suspensory (sling)-type fashion, 
maintaining a position covering the entire root sur- 
face. The full-thickness flap is mobilized to cover 
the entire surface of the barrier in an apicocoronal as 
well as a mesiodistal direction. Antibiotic coverage 
and an antibacterial mouthrinse may be prescribed 
for the postoperative interval. Weekly monitoring 
for possible infection is recommended. 



After a healing period of 4 to 6 weeks, a 
full-thickness flap is again reflected and is teased 
away from the external portion of the barrier. The 
barrier is then carefully removed to reveal a glossy 
and very vascular surface of new connective tissue. 
After the internal surface of the flap is stripped of 
epithelium by either sharp or rotary excision, the 
flap is placed to cover the entire surface of the new 
connective tissue. A periodontal dressing and sys- 
temic antibiotics or antibacterial mouthrinse may be 
used at the operator's discretion. 

Recent studies have favorably demonstrated 
the use of calcium sulfate (plaster of paris) as a re- 
sorbable barrier. In addition to a significantly reduced 
cost versus a PTFE barrier, the main advantage of this 
type of barrier is that the desired guided tissue regen- 
eration may be accomplished without the need for a 
second surgical procedure. The technique of flap re- 
flection, degranulation of the defect(s), and wound 
closure are similar to those used in other barriers (Fig. 
5-41), with primary wound closure over the barrier 
being the surgery's main objective. 



I 



Section 1 Planning and Preparation 







H 




Fig. 5-39. Guided tissue regeneration about an anterior tooth. A, Abscess at the mesial of the left lat- 
eral incisor. B, After initial debridement and 3 days of antibiotic therapy. Probing depth is 8 mm. C, Ra- 
diograph taken at the time of barrier placement. D, The mesial surface after degranulation. Note the de- 
gree of bone loss. E, The PTFE barrier placed at the CEJ completely covers the defect. F, Healing at 
5 weeks. Note the new connective tissue coronal to the barrier and the CEJ. G, When the barrier is re- 
moved, the new connective tissue can be seen at the mesial and buccal surfaces. H, Healing 10 days after 
barrier removal. I, HeaUng at 9 months. Note the minimal sulcular depth with excellent tissue health. 
There is sHght recession of the CEJ. 



Chapter 5 Periodontal Considerations 
ft C 



I 





Fig. 5-40. Guided tissue regeneration in a furcation defect. A, Buccal aspect of a mandibular second 
molar showing the defect. A curved furcation probe reveals 6 mm of vertical bone loss and 3 mm of hor- 
izontal loss. B, With reflection of the flap, the Class 1 1 defect can be seen. C, PTFE barrier in place at the 
CEJ. D, Healing at 6 weeks. Note the recession of the flap at the coronal surface of the barrier. E, After 
barrier removal. Note the new connective tissue apical to the margin of the gold crown. F, Healing at 10 
weeks. Despite minimum pocket depth, some loss of connective tissue is apparent. 



Restoration. Following the completion of 

guided tissue regeneration procedures, a period of 
healing is necessary that depends on the restorative 
needs of the patient. As a general guideline, 6 to 8 
weeks should be allowed before using displacement 
cord in the sulcus; this will allow tissue maturation. 
The subsequent restorative procedures are accom- 
plished as described earlier. 

MAINTENANCE 

Continued reexamination and evaluation of peri- 
odontal status are necessary to verify the treat- 
ment's success. Of particular importance is the iden- 
tification of areas where oral hygiene measures are 
partially effective or ineffective. The patient and the 
dentist must work together to preserve the health 
of the soft and hard tissues and prevent further 
periodontal breakdown or the recurrence of active 
disease. 

There is no standard maintenance schedule for 
patients requiring periodontal therapy. Some 
should be recalled only at 5- to 6-month intervals; 
others should be seen by the dentist (or periodon- 
tist) and the hygienist every 2 or 3 months. The 
maintenance regimen varies greatly among individ- 
uals and requires close coordination between the 
patient and the involved professionals. 



PROGNOSIS 

The progress, course, and outcome of gingival and 
periodontal disease are critically dependent on the 
patient. Without the ability and desire of the patient to 
maintain his or her teeth and periodontium, any treat- 
ment will ultimately fail. Determining a prognosis for 
the teeth and periodontium debilitated from mod- 
erate disease is therefore quite difficult. Unfortu- 
nately, failure is often the best teacher. 

There are many factors involved when one at- 
tempts to arrive at a prognosis for a tooth or an arch. 
With optimal intentions and the best technique, a fa- 
vorable result can be expected (even in the absence of 
good host resistance). Without them, treatment is 
doomed to ultimate failure. The age of the patient 
may help in predicting the success or failure of the 
treatment. Generally speaking, the prognosis is better 
for an older patient with a given amount of lost bone 
or tissue attachment than for a younger one. The 
older individual will often be more resistant to dis- 
ease, and the disease will have less effect. The amount 
of residual alveolar bone, the number of remaining 
teeth and their overall condition, any tooth mobility 
and the patient's general occlusion and systemic in- 
tegrity all can influence the outcome of therapy. 

Also important to the long-term stability and 
function of the dentition are the condition of the 



I 



Section 1 Planning and Preparation 
A B 






Fig. 5-41 . Guided tissue regeneration with a resorbable calcium sulfate barrier. A, Preoperative view 
of the maxillary right canine to be restored with a new crown. B, Flaps reflected and granulomatous tis- 
sue removed from the defect at the distal surface. C, Three-walled intrabony defect prepared for barrier 
placement. D, Defect is filled with dense calcium sulfate graft. E, Calcium sulfate slurry placed to act as 
a barrier and facilitate guided tissue regeneration. F, Minimal probing depths before final restoration. 
G, Favorable tissue contours after the elimination of the intrabony defect. 

(Courtesy Dr. V. Ng.) 



arches to be restored and the abihty of the restora- 
tive dentist to execute complex treatment plans 
without iatrogenically disturbing the gingiva and 
periodontium. This is a delicate undertaking and 
will adversely affect a periodontally unstable arch if 
not skillfully performed. 

SUMMARY 

The periodontium is the most important anatomic 
structure of the oral cavity in fixed prosthodontics. Its 
main component, the periodontal ligament, anchors 



the teeth in the alveolar processes and provides at- 
tachment, nutrition, tissue synthesis and resorption, 
and mechanoreception. The practitioner embarking 
on a restorative program must therefore first make an 
accurate periodontal diagnosis and then institute ef- 
fective treatment of any periodontal disease-whose 
main etiologic factor is neglected accumulations of 
plaque. Allowing the proper time for healing after 
periodontal surgery is also very important. The heal- 
ing time required depends on the design of the 
restoration and is critical to the correct placement of 
restorations near the free gingival margin. 



Chapter 5 Periodontal Considerations 



I 



Sfiidy Q^esfhff^ 



1. Discuss the different types of fibers that make up the periodontal Hgamenf. 

2. Describe and discuss the processes and sequence in the development of an advanced lesion of gingivitis- 
periodontltis. What specifically occurs at the cellular level? 

3. What are the classifications For furcation involvement? 

4. List at least eight indications for root amputation. Describe the controindications for root resection. 

5. List soft tissue surgical procedures that are primarily aimed at reducing probing depths. 

6. What is the typical sequence for periodontal therapy? 




QLOSSA^i} 



bifurcation: (n) (1615) 1: division into two branches 
2.' the site where a dingle structure divides into two 
parts, as in two roots of a tooth. 

crevicular epithelium: the nonkeratinized epithelium 
of the gingiva] crevice. 

crown-root ratio; the physical relationship between the 
portion of the tooth within alveolar bone compared 
with the portion not within the alveolar bone, as de- 
termined radiographically. 

debridement: (n) (ca. 1842): the removal of inflamed, 
devitalized, contaminated tissue or foreign material 
from or adjacent to a lesion, 

etiologic factors: the elements or influences that can be 
assigned as tlie cause or reason for a disease or lesion. 

free gingiva: the part of the gingiva that surrounds the 
tooth and is not directly attached to the tooth sur- 
face. 

free gingival margin: the imattached gingiva surround- 
ing the teeth in a coUar-hke fashion and demarcated 
from the attached gingiva by a shallow linear de- 
pression, termed the free gingival groove. 

fremitus: (n) (1879): a vibration perceptible on palpa- 
tion; in dentistry, a vibrat:ion palpable when the 
teeth come into contact- 

gingiva: (n, pi) -e: the fibrous investing tissue, covered 
by epithelium, which immediately surrounds a 
tooth and is contiguous with its periodontal mem- 
brane and with the mucosal tissues of the mouth. 

hemisection: (n): the surgical separation of a multi- 
rooted tooth, especially a mandibular molar, 
through the furcation in such a way that a root and 
the associated portion of the com may be removed. 

lengthening of the clinical crown: a surgical procedure 
designed to increase the extent of supragingival 
tooth structure for restorative or esthetic purposes 
by apically pi>sitioning the gingival margin, remov- 
ing supporting bone, or both. 

marginal gingiva: the most coronal portion of the gin- 
giva; often used to refer to the free gingiva that 
forms the wall of the gingival crevice in health. 



mucogingival junction: the junction of gingiva and 
alveolar mucosa. 

primary occlusal trauma: the effects induced by abnor- 
mal or excessive occlusal forces acting on teeth with 
normal periodontal support. 

reattachment: n: in periodontics, the reunion of epithe- 
lial and connective tissues with root surfaces and 
bone such as occurs after incision or injury. 

secondary occlusal trauma: the effects induced by oc- 
clusal forces (normal or abnormal) acting on teeth 
with decreased periodontal support, 

1. Bhaskar SN: Orban's oral histology and embryology, 

edll, St Louis, 1991, Mosby. 

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free and attached gingiva, J Penodontol 37:5, 
1966. 

4. Carranza FA Jr, Newman MG: Clinical periodon- 
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5. Schluger S et al: Periodontal disease: basic phenom- 
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tive interrelationships, ed 2, Philadelphia, 1990, 
Lea & Febiger. 

6. Lindhe J: Textbook of clinical periodontology, 

Copenhagen, 1989, Munksgaard. 

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Louis, 1990, Mosby. 

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1):223,1962. 

11. Schroeder HE, Listgarten MA: Fine structure of 
the developing epithelial attachment of human 

teeth, MonogrDev Biol 2:1, 1971. 



I 



Section i Planning and Preparation 



12. 



13. 



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15. 



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18. 



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JPeriodontol 36:177, 1965. 

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pig to sterile and non-sterile calculus, JPeriodon- 
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1994. 

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Guidelines for periodontal therapy, JPeriodontol 
69:405, 1998. 

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servations regarding early calculus formation in 
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scores, SAM-TR-67-97:l, July, 1967, USAF School 
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voted to the diseases and treatment of the investing 
tissues of the teeth and dental pulp, Chicago, 1915, 

Medico-Dental Publishing. 
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treatment of periodontitis simplex, JPeriodontol 
27:144,1956. 

Hassell TM: Epilepsy and the oral manifesta- 
tions of phenytoin therapy, MonogrOralSci 9:1, 
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seous surgery, JPeriodontol 32:275, 1961. 
Levin MP et al: Healing of periodontal defects 
with ceramic implants, J Clin Periodontol 1:197, 
1974. 

Klingsberg J: Periodontal scleral grafts and com- 
bined grafts of sclera and bone: two year 2cp- 
praissil, J Periodontol 45:262, 1974. 
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tal disease. Acta Odontol Scand 13:235, 1956. 
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in a dog and a rhesus monkey, JPeriodontol 
28:125,1957. 

Robinson RE: The osseous coagulum for bone 
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46:18,1970. 

Mellonig JT et al: Chnical evaluation of 
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logical evaluation of autogenous ihac bone 
grafts in humans. I. Wound healing 2 to 8 

months, J Periodontol 44:599, 1973. 

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ing procedures, JPeriodontol 48:570, 1977. 
Kenney EB et al: Bone formation within porous 
hydroxylapatite implants in human periodontal 
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Chapter 5 Periodontal Considejations 



I 



57. Schepers EJG, Ducheyne P: The apphcation of 69. 

bioactive glass particle of narrow size range as a 
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nal study comparing apically positioned flaps, 73. 
with and without osseous surgery, int J Periodont 

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scaling, osseous surgery and modified Widman 
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55. Kaldahl W et al: Evaluation of four modalities of 
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ing attachment level and recession changes, J Pe- 
riodontal 59:783, 1988. 

56. Baima RE: Considerations for furcation treat- 77. 
ment. I. Diagnosis and treatment planning, 

J Prosthet Dent 56:138, 1986. 78. 

57. Abrams L, Trachtenberg DI: Hemisection- 
technique and restoration. Dent Clin North Am 
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58. Highfield JE: Periodontal treatment of multi- 
rooted teeth, A ust Dent J 23:91, 1978. 

59. Gher ME, Vernino AR: Root anatomy: a local 

factor in inflammatory periodontal disease, int J 80. 

Periadant Rest Dent 1(5):52, 1981. 

60. Cohen S, Bums RC: Pathways af the pulp, Qd 5, St 81. 

Louis, 7997, Mosby. 

61. Ash MM: Wheeler's dental anatomy, physiology, 

and occlusion, ed 8, Philadelphia, 7995, WB 82. 

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63. Ross IE, Thompson RH: A long-term study of 
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65. Amen CR: Hemisection and root amputations, 
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66. Newell DH, Morgano SM, Baima RE: Eixed 
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57:400, 1987. 88 

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Haskell EW, Stanley HR: A review of vital root 
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ment. 111. Restorative therapy, J Prosthet Dent 
58:145,1987. 

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Periodont 14:618, 1987. 



I 



Section 1 Planning and Preparation 



89. Caffesse RG et al: Class 1 1 furcations treated by 
guided tissue regeneration in humans: case re- 
ports, J Periodontal 61:510, 1990. 

90. Vernino AR et al: Use of biodegradable polylac- 
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grade 1 1 periodontal furcation defects in hu 
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treatment of class 1 1 furcation involvements with 
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riodontol 70:8, 1999. 

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mentation at titanium implants: a report on ten 



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for implants placed into extraction sockets and 
for implant dehiscences: surgical techniques and 

case reports, Intj Periodont Rest Dent 10:376, 1990. 

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generation, Compend Contin Educ Dent 13:226, 
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materials, J Periodontal 67:236, 1996. 

97. Kim C-K et al: Periodontal repair with intrabony 
defects treated with a calcium sulfate implant 
and calcium sulfate barrier, j Periodontal 69:1317, 
1998. 









Mouth Preparation 



definitive periodontal 

treatment 
foundation restorations 
minor tooth movement 



multidisciplinary 
considerations 
occlusal adjustment 
treatment sequence 



As the scope of fixed prosthodontics has expanded, 
it has become increasingly clear that failures are of- 
ten attributable to inadequate mouth preparation. 
In this case, mouth preparation refers to the dental 
procedures that need to be accomplished before 
fixed prosthodontics can be properly undertaken. 
Rarely are crowns or fixed partial dentures pro- 
vided without initial therapy of a multidisciplinary 
and often extensive nature, because the etiologic 
factors that lead to the need for fixed prosthodontics 
also promote other pathologic conditions (caries 
and periodontal disease are the most common). 
These must be corrected as an early phase of treat- 
ment. Fixed prosthodontics will be successful only 
if restorations are placed on well-restored teeth in a 
healthy environment, a fact that can become ob- 
scured in the misguided attempt to try to help a pa- 
tient by accelerating treatment; unfortunately, such 
action often leads to unforgivable failure. 

This chapter reviews the ways in which treat- 
ment by the different dental disciplines relates to 
fixed prosthodontics. Obviously, detailed descrip- 
tions of the particular procedures are beyond the 
scope of this text. 

Comprehensive treatment planning will ensure 
that mouth preparation is undertaken in a logical 
and efficient sequence aimed at bringing the teeth 
and their supporting structures to optimum health. 
Equally important is the need to educate and moti- 
vate the patient to maintain long-term dental health 
through meticulous oral hygiene practices. As a 
general plan, the following sequence of treatment 
procedures in advance of fixed prosthodontics 
should be adhered to: 

1 . Relief of symptoms (chief complaint) 

2. Removal of etiologic factors (e.g., excavation 
of caries, removal of deposits) 



3. Repair of damage 

4. Maintenance of dental health 

The following list describes a typical sequence 
in the treatment of a patient with extensive dental 
disease-including missing teeth, retained roots, 
caries, and defective restorations: 

Preliminary assessment (Fig. 6-1, A) 

Emergency treatment of presenting symptoms 
(Fig. 6-1, B) 

Oral surgery (Fig. 6-1, C) 

Caries control and replacement of existing 
restorations (Fig. 6-1, D) 

Endodontic treatment (Fig. 6-1, E) 

Definitive periodontal treatment, possibly in 
conjunction with preliminary occlusal therapy 
(Fig. 6-1, F) 

Orthodontic treatment 

Definitive occlusal treatment 

Fixed prosthodontics (Fig. 6-1, G, H) 

Removable prosthodontics (Fig. 6-1, 1) 

Follow-up care 

However, the sequence of preparatory treatment 
should be flexible. Two or more of these phases 
are often performed concurrently. Carious lesions 
or defective restorations will often prevent proper 
oral hygiene measures, and their elimination or 
correction must be a part of preparatory treat- 
ment. If caries control results in a pulpal exposure 
or exacerbates an existing chronic pulpitis, en- 
dodontic treatment may be needed earlier than 
anticipated. When the primary symptoms have 
been eliminated, the occlusal needs of the patient 
are carefully evaluated through clinical examina- 
tion and the study of articulated diagnostic 
casts. Extensive treatment of both arches simultane- 
ously may be beyond the scope of the nonspe- 
cialist, and the use of cross-mounted diagnostically 
mounted casts should be considered (see p. 75). 
This enables treatment of each arch to be ac- 
complished predictably and independently. Only 
when preparatory occlusal treatment is completed 
will the patient be ready for definitive restorative 
care. 



135 



I 



Section 1 Planning and Preparation 



B 





(2^yj^ 







Relief of 

symptoms. 






^t^Jju^ 



Fig. 6- 1 . Sequence of treatment. A, The patient has pain that seems to originate from the maxillary 
right central incisor. In addition, there are several missing teeth, retained roots, caries, calculus, and de- 
fective restorations. B, Relief of the acute problem by endodontic treatment of the incisor. C, Removal of 
deposits and unrestorable teeth. D, Caries are controlled, and defective restorations are replaced. The 
progress of ongoing disease has been halted. E, Endodontic treatment is undertaken, and post-and-cores 
and a provisional restoration are placed. F, Definitive periodontal treatment is performed. 



Chapter 6 Month Pr eparation 



I 





rf 



n 







Defiiutive 
pros thodon tic 
treatment. 



Fig. 6-1 , cont'd. G, Teeth are prepared for the final restoration. H, The fixed restorations are com- 
pleted. I, Active phase of the treatment has been accomplished. NOTE: predictable management of com- 
plex prosthodontics involving fixed and removable prostheses can be facilitated by adopting the technique 
described on p. 78. 



^JORAL SURGERY 



SOFT TISSUE PROCEDURES 

Any soft tissue abnormalities that may require sur- 
gical intervention should be recognized during the 
initial or radiographic examination. If necessary, the 
patient can be referred to an oral surgeon for further 
consultation and/or treatment. Diagnosis of patho- 
logic conditions can be difficult, and the general 
practitioner should make the appropriate referral to 
a specialist when there is doubt. 

Elective soft tissue surgery may include alter- 
ation of muscle attachments, removal of a wedge of 
soft tissue distal to the molars, increase of the 
vestibular depth, or modification of edentulous 
ridges to accommodate fixed or removable partial 
prostheses (Fig. 6-2). 

HARD TISSUE PROCEDURES 

Simple tooth removal is the most common surgical 
procedure involving hard tissue. It should be per- 
formed as early during treatment as possible for 
maximum healing time and osseous recontouring. 

Tuberosity reduction (Fig. 6-3) is also common, 
especially when there is inadequate space to accom- 
modate a prosthesis. Although maxillary or man- 



dibular tori (Fig. 6-4) seldom interfere with the fab- 
rication of a fixed partial denture, their excision may 
make it easier to design a removable partial denture 
and occasionally will improve access for oral hy- 
giene measures. 

Impacted or unerupted supernumerary teeth 
should be removed if damage to adjacent structures 
can be avoided. 

ORTHOGNATHIC SURGERY 

Candidates for orthognathic surgery require care- 
ful restorative evaluation and attention before 

treatment. Otherwise, an expected improvement in 
the facial skeleton may be accompanied by unex- 
pected occlusal dysfunction. After surgery, the con- 
nection between plaque control, caries prevention, 
and periodontal health should be stressed to the 
patient. 

IMPLANT-SUPPORTED FIXED PROSTHESES 

Successful implant dentistry requires meticulous se- 
lection of the patient and skillful execution of the 
chosen technique. A team approach to treatment is 
strongly recommended with close cooperation be- 
tween the specialties (see Chapter 13). 



I 



Section 1 Planning and Pr eparation 




Fig. 6-2. A to D, Soft tissue surgery to correct an unfavorable edentulous ridge before FPD fabrication. 



B , 




Fig. 6-3. Tuberosity reduction was indicated for this pa- 
tient to accommodate a mandibular removable partial den- 
ture. A, Preoperative and, B, postoperative appearances. 
(Courtesy Dr. J. Bergamini.) 




Fig. 6-4. A, Mandibular torus requiring surgical reduc- 
tion before the fabrication of an RPD. B, Buccal torus that 
was interfering with oral hygiene. 



Chapter 6 Mouth Preparation 



I 



||t]CARIES AND EXISTING 
RESTORATIONS 

Crowns and fixed partial dentures are definitive 
restorations. They are time-consuming and expen- 
sive treatment options and should not be recom- 
mended unless an extended lifetime of the restora- 
tion is anticipated. Often, teeth requiring crowns 
are severely damaged or have large existing 
restorations. Any restoration on such teeth must be 
carefully examined and a determination made re- 
garding its serviceability. If doubt exists, the 
restoration should be replaced. Time spent replac- 
ing an existing restoration that in retrospect might 
have been serviceable is a modest price to pay for 
the assurance that the foundation will be caries free 
and well restored. Studies have shown that accu- 
rately detecting caries beneath a restoration with- 
out its complete removal can be very difficult. 
Even on caries-free teeth, an existing restoration 
may not be a suitable foundation. Preparation de- 
sign is different for a foundation than for a conven- 
tional restoration, particularly regarding the place- 
ment of retention. Generally, when a crown is 
needed, the dentist should plan to replace any ex- 
isting restorations. Although most teeth will re- 
quire foundation restorations, small defects result- 
ing from less extensive lesions can often be 
incorporated in the design of a cast restoration or 
can be blocked out with cement (Fig. 6-5). The lat- 
ter is recommended on axial walls where an under- 
cut would otherwise result. If a small defect is pre- 
sent on the occlusal surface, however, it may be 
better to incorporate it into the final restoration 
than to block it out. The difficulty, of course, is an- 
ticipating this during the preparatory phase of 
treatment. Assessment is more difficult when an ex- 
isting crown or FPD is being replaced. Then the ex- 
tent of damage can be seen only after the defective 
restoration has been removed. 

^]l FONDATION RESTORATIONS 

A foundation restoration, or core, is used to build a 
damaged tooth to ideal anatomic form before it is 
prepared for a crown. With extensive treatment 
plans, the foundation may have to serve for an ex- 
tended time. It should provide the patient with ad- 
equate function and should be contoured and fin- 
ished to facilitate oral hygiene. Subsequent tooth 
preparation is greatly simplified if the tooth is built 
up to ideal contour. Then it can be prepared essen- 
tially as if it were intact. Guide grooves can be used 
to facilitate accurate occlusal and axial reduction 
(see Chapter 8), and the preparation design will be 
consistent from tooth to tooth. The skills learned 




Fig. 6-5. Small defects (arrow) that would create under- 
cuts are best blocked out intraorally with cement or resin. 



preparing preclinical manikins with "ideal" teeth 
can be readily transferred to clinical practice. 

SELECTION CRITERIA 

Selection of the foundation material depends on the 
extent of tooth destruction, the overall treatment 
plan, and operator preference (Fig. 6-6). The effect 
of subsequent tooth preparation for the cast restora- 
tion on the retention and resistance of the founda- 
tion should be considered. Retention features such 
as grooves or pinholes should be placed sufficiently 
pulpal to allow adequate room for the definitive 
restoration. Adhesive retention may be helpful in 
preventing loss of the foundation during tooth 
preparation. 

Dental Amalgam. Despite its limitations, amal- 
gam is still the material of choice for most founda- 
tion restorations on posterior teeth. It has good 
resistance to microleakage and is therefore recom- 
mended when the crown preparation will not ex- 
tend more than 1 mm beyond the foundation-tooth 
junction.' It can be shaped to ideal restoration form 
and serves well as an interim. It has better strength 
than the glass ionomers, and retention can be pro- 
vided by undercuts, pins, or slots. Adhesive bond- 
ing systems such as those based on 4-META* are 
also available and may reduce leakage of the 
restoration. Additional retention may be pro- 
vided with the use of polymeric beads supplied 
with the Amalgambond system. Amalgam re- 
quires an absolutely rigid matrix for proper con- 
densation. Otherwise the foundation will break. 
Matrix placement can be demanding when restor- 
ing a tooth with little remaining coronal tissue. This 
is discussed in the step-by-step procedure on p. 140. 
Amalgam has a longer setting time than the other 



*4-Methacryloxy ethyl trimellitate anhydride. 



I 



Section 1 Planning and Preparation 






Fig. 6-6. The placement of a foundation restoration depends on the extent of damage to the tooth and 
should always be designed with the definitive restoration in mind. A, Cement. This is suitable when 
damage is minimal. B, Amalgam. C, Pin- retained amalgam. D, Cast gold. E, Post- and- core. 
(See Chapter 12.) 



foundation materials. This normally delays crown 
preparation to a subsequent patient visit. When this 
presents a problem, a rapid- setting, high-copper, 
spherical alloy should be chosen. These can be pre- 
pared for a crown about 30 minutes after placement. 
Spherical amalgams are advantageous for founda- 
tion restorations because they have greater early 
strength than admixed materials, which makes frac- 
ture soon after placement less of a problem." 

Glass lonomer Cement. This is a suitable 
choice for a small lesion. The material sets rapidly, 
enabling crown preparation to be performed with 
Hmited delay. When placed correctly, it exhibits ad- 
hesion to dentin, although conventional undercut 
retention is needed to supplement this. Glass 
ionomers designed for use as a core or base are ra- 
diopaque; restoration formulations are more radio- 
lucent than dentin and should not be used as a core, 
because their radiographic appearance may suggest 
recurrent caries. The presence of fluoride in glass 
ionomers may help prevent recurrent caries. The 
chief disadvantage of glass ionomers is their com- 
paratively low strength, although newer formula- 
tions have improved properties. At this time, glass 
ionomers are inferior to amalgam or composite 
resin for the restoration of extensive lesions. 

Composite Resin. Composite resin exhibits 
many of the advantages of glass ionomers. It does 
not require condensation and sets rapidly. Formula- 
tions are available that release fluoride, which may 
provide an anticariogenic benefit.'" Bonding is 
achieved with a dentinal bonding agent or by etch- 



ing a glass ionomer liner. Neither method develops 
the bond strengths needed to withstand high masti- 
catory forces, and conventional undercut retention 
is also needed. There are concerns about continued 
polymerization of the resin and its high thermal ex- 
pansion coefficient, which may lead to microleak- 
age of the crown." Also of concern is the moisture 
sorption properties of composite resin that causes 
delayed expansion and may lead to axial binding of 
crowns made on composite resin cores. Delayed 
expansion is not a problem with traditional glass 
ionomer, but it is a problem with the resin- 
ionomer hybrids and the compomer materials. 
Conventional tooth-colored composite resin is not 
recommended as a foundation material, because it 
is difficult to discern the composite-tooth junction. 
Special colored core materials should be used. 

Pin-retained Cast Metal Core. A cast metal 
core should be considered for an extensively dam- 
aged tooth. The cemented foundation is retained 
by tapered pins. The preparation requires careful lo- 
cation and placement of the pinholes but otherwise 
is straightforward. The foundation is fabricated in 
the laboratory as an indirect procedure. This in- 
creases the complexity and expense of treatment but 
facilitates obtaining good preparation form. 

Advantages and disadvantages of the available 
materials are summarized in Table 6-1. 

STEP-BY-STEP PROCEDURES 

Amalgam Core (Fig. 6-7) 

1. Isolate the tooth. Rubber dam isolation is 
strongly recommended for moisture control. 



Chapter 6 Mmifh Preparation 



I 











TABLE 6-1 




Advantages 


Disadvantages 


Recommended Use 


Precautions 


Amalgam 


Good strength 
Intermediate restoration 


Preparation delay 
Condensotion 
Corrosion 
No bonding* 


Most foundations 


Well-supported matrix 


Gloss ionomer 


Rapid setting 

Adhesion 

Fluoride 


Low strength 
Moisture sensitivet 


Smaller lesions 


Moisture control 


Composite resin 


Rapid setting 
Ease of use 
Bonding 


Thermol expansion 
Setting contraction 
Delayed expansion 


Smaller lessons 
Anterior teeth 


Moisture control 


Cast gold 


Highest strength 
Indirect procedure 


Two- visit procedure 
Provisional needed 


Extensive lesions 


Alignment of pinholes 



*Bonding can be acliieved witli 4-META products. 
Resin-modified formulations are less sensitive. 



infection control, and optimum visibility. 

Placement follows techniques developed for 
conventional amalgam restorations, although 
with extensively damaged teeth, placing the 5. 

dam can be a problem. Sometimes cotton roll 
isolation must suffice. 

2. Design the tooth preparation with the in- 
tended cast restoration in mind. Be sure that 
the cast restoration does not ehminate reten 
tion of the foundation. The preparation will 
differ somewhat from a conventional amal- 
gam restoration. The ensuing discussion 
highlights these differences .21 

3. Limit the extent of the outline form. In con- 
trast to conventional amalgam preparations, 
which are extended to include unsupported 
enamel and the deep occlusal fissures, a less 6. 
extensive outline is recommended for foun- 
dation restorations, because the fissures and 
contacts are removed during crown prepara- 
tion. Although minimizing foundation out- 
line can help conserve supporting tooth 
structure, the foundation should be adequate 

for the detection of any carious lesions (Fig. 
6-7, A). 

4. Retain unsupported enamel if convenient. 
For a conventional amalgam tooth prepara- 
tion, unsupported enamel must always be re 
moved; otherwise, the enamel may fracture 
during function and leave a deficient margin. 
However, for a foundation restoration, the 7. 
unsupported enamel may be preserved most 
effectively if it is substantial enough to with- 
stand condensation forces and if it can be de- 
termined whether the enamel-dentin junc- 



tion is caries free. Preserving unsupported 
enamel may facilitate matrix placement and 
improve amalgam condensation (Fig. 6-7, B). 
Finish the cavosurface margins. For conven- 
tional amalgam restorations, cavosurface 
margins of 90 degrees are needed to mini- 
mize the potential for fracturing the enamel 
and amalgam during function. However, for 
foundation restorations, the amalgam-tooth 
interface will not be subjected to high stresses 
(they are protected by the crown), and mar- 
ginal fracture is not likely to be a problem. 
Therefore, a 46- to 136-degree margin is ac- 
ceptable. Furthermore, such a margin will 
conserve useful tooth substance and improve 
condensation (Fig. 6-7, C). 
Remove any carious dentin carefully and 
thoroughly with a hand excavator or large 
round bur in a low-speed handpiece. Discol- 
ored but hard dentin can be left on the pulpal 
wall, but caries-affected areas at the 
enamel-dentin junction should be removed 
completely. If a pulp exposure occurs during 
the preparation, whether carious or mechani- 
cal, endodontics or tooth removal will be 
necessary. A direct pulp cap is not a good 
choice for a tooth requiring an FPD; however, 
if endodontics is elected and the pulp cannot 
be extirpated immediately, a suitable seda- 
tive dressing should be placed. 
Create optimum resistance form. Good resis- 
tance to masticatory forces is as critical for a 
foundation as for a conventional restoration. 
Whenever possible, the tooth preparation 
should be perpendicular to the occlusal 



I 



Section 1 P1^^nning nnri Prpp^r^fi^ri 




' r ^ 



Fig. 6-7. The principles of preparation design for an amalgam foundation restoration differ slightly 
from those for a conventional extensive amalgam restoration. A, The outline form of a foundation need 
not include fissures or proximal or occlusal contacts, provided complete caries removal can be accom- 
plished. B, Unsupported enamel (arrow) can sometimes be left when preparing a foundation restoration. 
It may facilitate matrix placement and is removed when the crown is prepared. C, Acute cavosurface 
margins are acceptable for a foundation restoration but not for a definitive amalgam. D, Resistance form 
is improved by preparing the tooth in a series of steps perpendicular to the direction of occlusal force. E, 
When pin retention is used, pinholes should be drilled slightly pulpal and at an angle to the root surface 
(solid line) ^^ compared to the way they are placed for a conventional extensive amalgam restoration 
(dashed line), xhis will ensure retention for the foundation remains after crown preparation. 



Chapter 6 Mouth Preparation 



I 



forces. If a sloping axial wall exists, it should 
be modified into a series of steps to enhance 
resistance form. 
8. Be sure that the foundation restoration has 
adequate retention (augmented if necessary 
by pins, slots, or wells). Proper placement of 
retention features is essential to the prepara- 
tion of a successful foundation. The features 
must be incorporated into the design so they 
are not eliminated during preparation of the 
crown (Fig. 6-7, D, E). 
This can be a particular problem with the ex- 
tensive reduction necessary for a metal-ceramic 
restoration. Pin placement is dictated by root furca- 
tions and the size of the pulp chamber. Generally, 
pins should be placed further pulpally than when 
conventional extensive pin amalgams are being pro- 
vided; to prevent pulp perforation, they should be 
positioned at a slight angle to the long axis of the 
tooth. If a pin is slightly exposed during crown 
preparation, this may not be a problem-in contrast 
to the conventional pin-amalgam restoration. With 
a foundation restoration, the pin- amalgam interface 
receives little stress during function. 

Retention can also be provided by slots or wells. 
These will create less residual stress in the dentin 
and will thus reduce the risk of pulp exposure or 
damage . They should be placed pulpal to the in- 
tended crown margin, at a depth of about 1 mm, 
with a small carbide bur. Careful condensation of 
amalgam into the slots will ensure good restoration 
retention. 

Bonding agents can assist amalgam retention, but 
adhesion is not adequate to resist occlusal loading. 
Currently retention is best provided by conven- 
tional means. An example of the use of bonding 
agents appears in Figure 6-8. If bonding agents are 
used, the clinician should follow the manufacturer's 
directions about storage and manipulation. 

Bases and Varnishes. A base is necessary to 
prevent thermal irritation if the preparation ex- 
tends close to the pulp. A material with good 
physical properties, such as glass ionomer or zinc 
phosphate, should be chosen, because weaker 
materials are likely to fracture during amalgam 
condensation. Excessively thick bases should 
be avoided if they would leave inadequate thick- 
ness of amalgam foundation after tooth prepara- 
tion. Postoperative sensitivity can be prevented 
with two or more coats of cavity varnish or a 
dentin bonding agent. The coats should be placed 
after any pinholes are drilled but before the pins 
are placed to avoid material at the pin-amalgam 
interface. 



Calcium hydroxide liners should be reserved for 
use in deep cavities when a microscopic pulp expo- 
sure is suspected. They generally have low strength 
and do not resist condensation forces well. Macro- 
scopic exposures should receive endodontic treat- 
ment or, if direct pulp-capping is the only option, a 
conventional pin- amalgam should be placed as the 
definitive restoration, at least until the success of the 
pulp-capping can be guaranteed. 

Matrix Placement. A rigid, well-contoured ma- 
trix allows the amalgam to be properly condensed 
and facilitates carving. However, it can present a 
problem when much tooth structure is missing. Con- 
ventional matrix retainers, such as the Tofflemire, 
are unstable if both the lingual and the buccal walls 
are missing. A circumferential matrix (e.g., the Au- 
tomatrix*) is useful for extensive restorations. Alter- 
natives include copper bands or orthodontic bands. 
These are removed by cutting with a bur after the 
amalgam has set. Stability of the matrix is improved 
by proximal wedging, by crimping to shape, and by 
using modeling plastic or autopolymerizing acrylic 
resin for external stabilization27<Fig. 6-9). 

Condensation. Condensation follows conven- 
tional practice, with particular attention paid to 
condensing into wells and around pins. If the 
foundation is prepared during the same visit, a 
high-copper spherical alloy is chosen. A mechanical 
condenser is useful for large amalgam restorations. 

Contouring and Finishing. Care is needed to 
prevent amalgam fracture during matrix removal. 
After allowing time for setting, the dentist trims the 
amalgam away from the occlusal edge of the matrix 
and removes the wedges and matrix retainer. At this 
stage it is helpful to cut the buccal ends of the ma- 
trix band with scissors close to the tooth. Then the 
band can be pulled through the proximal contacts 
toward the lingual. Pulling the band occlusally is 
more likely to fracture the freshly placed amalgam. 

Contouring follows conventional practice if the 
foundation is to serve for a significant period. Such 
a foundation should also be finished to facilitate 
plaque control. If the foundation is to be prepared 
shortly after placement, a more rudimentary oc- 
clusal contour is acceptable. However, the occlusal 
contour should be adequate to provide proper tooth 
stability. Moreover, all margins should be carved 
properly, because flash will lead to plaque retention 
and will make crown margin placement difficult. 



*Caulk, Dentsply. 



I 



Section 1 Planning and Preparation 
A B 




Fig. 6-8. Adhesives such as AmalgamBond, a 4-META product, maybe helpful in retaining shallow 
amalgams. A, Class V caries in a mandibular second molar. B, Shallow Class V cavity is prepared and 
dentin conditioned. Good isolation is essential when using adhesives. C, After rinsing and drying, the 
adhesive agent is brushed into the prepared cavity. This is followed by the mixed adhesive liner. D, The 
amalgam is condensed while the liner is still wet. E, The finished restoration. 

(Courtesy Parkell Products, Inc. ) 




Fig. 6-9. Autopolymerizing resin can help stabilize the 
matrix for an amalgam foundation restoration. 

Glass lonomer Core (Fig. 6-10) 

1. Isolate the tooth. As with amalgam prepara- 
tions, moisture control is critical with glass 
ionomer preparations. The setting material is 
very sensitive to moisture. When it is set, 
it must not be allowed to dry out or it will 
deteriorate rapidly. The light-cured, resin- 
modified glass-ionomers are less sensitive to 
early moisture " 

2. Prepare the tooth for a casting; then remove 
any existing restorations and bases, excavate 
caries, and create the undercut retention. 
Glass ionomer is best for small foundations 
on teeth with at least two axial walls of sound 
dentin remaining. Presently available glass 




Fig. 6-1 0. The foundation restoration for this crown was 
a silver-containing glass ionomer. 



ionomers are not strong enough to be used for 
large pin-retained foundations. (Often they 
are chosen when the foundation and crown 
preparation are completed during one visit.) 
After tooth preparation and the creation of 
undercuts, glass ionomer is used to build the 
tooth up to ideal preparation form, provided 
any defects are relatively small. Adhesion to 
dentin can be enhanced by removing some of 
the smear layer with a chemical agent. How- 
ever, excessive removal of the smear layer is 
not recommended, because it could lead to 
pulp irritation. A 20-second application with a 
dentin-conditioning agent that contains 10% 
polyacrylic acid should be sufficient. Dry the 



Chapter 6 Month Preparation 



I 



tooth with a cotton pledget before placing the 
ionomer; do not use an air syringe. 

3. Syringe the glass ionomer onto the tooth, be- 
ing careful not to create voids at the ce- 
ment-tooth interface. Remember: With the 
conventional self-hardening formulations, 
adhesion of glass ionomer to tooth structure 
occurs only if the cement is placed rapidly af- 
ter mixing; 10 seconds should be allowed for 
loading the syringe and 10 seconds for place- 
ment and manipulation. Some manufacturers 
provide an encapsulated delivery system that 
helps place the cement rapidly. A matrix is 
not normally needed for a small cavity, since 
the core materials do not slump. After injec- 
tion, the cement can be rapidly manipulated 
to shape. However, manipulation beyond 
3 or 4 seconds will disturb the developing 
bond and should be avoided. It is better to 
overfill slightly and reprepare the tooth after 
it has set (under 5 minutes for the metal-con- 
taining cements). If a resin-modified glass- 
ionomer is used, this is light-cured according 
to the manufacturer's recommendations. 

4. Finish the preparation as for other types of 
cores. Conventional glass ionomers are ex- 
tremely sensitive to drying, even when they 
are set, a fact that should be kept in mind 
when fabricating the crown preparation, 
making the provisional, or making the im- 
pression. Resin-modified formulations are 
less moisture sensitive. Vital teeth are also 
sensitive to desiccation, so this consideration 
should not modify normal practice. 

Composite Resin 

Composite resin foundations are much stronger 
than glass ionomer foundations, a difference that 
correlates with the higher diametral tensile strength 
of the composite 3° They are strong enough for 
larger pin-retained cores. However, the current ma- 
terials have disadvantages, particularly their ab- 
sorption of moisture and high thermal expansion, 
which has led many dentists to avoid composite 
resin foundations entirely. 

Moisture Control. Composite resins are sensi- 
tive to moisture contamination, and rubber dam iso- 
lation is strongly recommended. 

Preparation. Because the material sets rapidly 
(about 5 minutes), composite resin is generally cho- 
sen if the dentist wishes to place the foundation and 
prepare the tooth during the same visit. The crown 
is prepared to approximate shape first, and then ex- 



isting restorations and caries are removed. A glass 
ionomer is an appropriate choice of liner, with addi- 
tional retention being provided by pins. For conve- 
nient access, the pinholes can be prepared and the 
liner placed before the pins are seated. 

Placement. Both light-cured and chemically 
cured core composites are available. Light-cures 
have the convenience of extended working time, 
but there is concern about the adequacy of poly- 
merization, especially around the pins S The au- 
topolymerizing materials need to be mixed and 
placed quickly, preferably with the aid of a compos- 
ite syringe.* A Mylar matrix is used to confine them 
and provide good adaptation. 

Finishing. Composite resin core materials are 
easily prepared with conventional tooth prepara- 
tion diamonds. 

Pin-retained Cast Core (Fig. 6-11) 
As with glass ionomer and composite resin cores, 
cast cores are used to build a tooth to ideal prepara- 
tion form without the need for matrix placement or 
condensation. However, they require the additional 
steps of an indirect procedure. 

1. Prepare the tooth to approximate shape for a 
crown, removing any existing restorations 
and caries. Remove or block out all under 
cuts, and evacuate any weakly supported 
dentin. 

2. Make pinholes using the small- diameter 
twist drill that comes with self-threading 
pins. The locations for these pins will be sim 
ilar to those of self- threading pins, but all 
restorations using cast pins must have a com- 
mon path of withdrawal. Prepare a flat area 
around each pin location with a large tapered 
carbide, and make the starting point for the 
pinhole with a small round bur. Pilot holes 
2 mm deep are made for each pin, with the 
small- diameter twist drill carefully oriented 
in the planned path of withdrawal. Using a 
mouth mirror to observe the angulation of 
the drills helps ensure correct alignment. 
Plastic patterns are available for both tapered 
and parallel-sided cast pins. We prefer the ta- 
pered pins because they allow some leeway 
in paralleling the holes, and their tapered 
shape provides strength where needed. How- 
ever, the parallel design is more retentive. 
The plastic patterns are manufactured to 
match specific bur sizes, which are used to 

*Centrix Inc., Milford, Conn. 



I 



Lanning and Preparation 




^iraajBTlca: 



Fig. 6-11. Pin-retained cast core. A, Badly damaged maxillary molar. The pulp is healthy. B, Caries 
excavated and the tooth prepared for a pin-retained cast core. C, Four tapered pins provide retention. 
D, The completed foundation. 



enlarge the pilot holes. To avoid overheating, 
always use low rotational speeds when 
drilling pinholes. Finally, a small counter- 
sink is created where the pinhole meets the 
gingival floor; this will facilitate forming a 
die that is free of defects and will help pre- 
vent pin fracture. 

3. Make the impression with an elastomeric ma- 
terial, using a lentulo to fill the pinholes. 
Place a small quantity of mold-release sub 
stance (e.g., die lubricant) into each pinhole 
with a paper point to prevent tearing of the 
impression. As an alternative, use the plastic 
pattern for the impression. 

4. Fabricate a provisional restoration. This pro- 
cedure is described in Chapter 15. Place 
loose-fitting pins in the pinholes to provide 
retention. If retention is not a problem, avoid 
introducing luting agent into the pinholes 
when cementing the provisional. 

5. 6, and 7. Dies, waxing, and casting. These 
steps present no special problems. Plastic patterns 
are used to form the pins. If a tapered pin fits loosely, 
it can be shortened with a scalpel until it fits prop- 
erly. Retention of pins in the wax pattern is accom- 
plished by flattening the heads of the pins with a 
heated instrument. The foundation should be waxed 
as exactly as possible to final preparation form, with 
particular attention paid to the occlusal reduction. If 



it is properly performed, a cast core should require 
minimum finishing in the mouth. If necessary, the 
die can be sectioned, trimmed, and mounted to fa- 
cilitate this. The pattern is then invested and cast 
with the same regimen as for inlay castings (which 
generally require slightly less expansion than 
crowns). Factors that affect casting expansion are 
described in Chapter 22. 

8. For try-in and cementation, do all grinding or 
adjustment of the casting before the cementa- 
tion. The newly set cement may be damaged 
by vibration. To be acceptable, the fit of the 
cast foundation should be good, with com- 
plete seating and no discernible rock. A small 
marginal defect can be tolerated, provided it 
is not indicative of incomplete seating, be- 
cause the margins will be completely covered 
by the definitive restoration. During cemen- 
tation, completely fill the pinholes with ce- 
ment; this can be done with a lentulo. 

^] ENDODONTICS 

ASSESSMENT 

During the initial data collection, attention must be 
directed toward potential endodontic needs of the 
patient. The clinical examination should include vi- 
tality testing of all teeth in the dental arch. This may 
be done with an electric pulp tester, an "ice pencil" 



Chapter 6 Mouth Preparation 



I 



(conveniently made by filling an anesthetic needle 
cap with water and freezing), an aerosol cryogen 
spray, or heated gutta-percha. Tenderness to percus- 
sion should also be noted. Any abnormal sensitivity, 
soft tissue swellings, fistulous tracts, or discolored 
teeth will prompt a suspicion of pulpal involvement. 
Patients who have definite symptoms seldom 
present problems in diagnosis, because pain is gen- 
erally their chief complaint. When there is doubt 
concerning pulpal health, however, patients should 
be examined radiographically during the mouth 
preparation phase, and the films should be carefully 
inspected for signs of periapical disease (a radiolu- 
cency or widening of the PDL space). When there is 
doubt regarding the endodontic prognosis of a 
tooth, radiographic findings (Fig. 6-12) should al- 
ways be evaluated in reference to the results of per- 
cussion and vitality tests. 

TREATMENT 

As a general rule, conventional (or orthograde) 
rather than surgical (or retrograde) endodontics 
should be performed if possible-not only because 
additional trauma results from the surgical ap- 
proach but also because apicoectomy adversely af- 
fects the crown/root ratio and thus the support of 
the planned prosthesis. If an existing post prevents 
access to a recurrent periapical lesion, the post can 
usually be removed. (A Masserann kit has shown 
some success with this-see Chapter 12.) When a 
post-and-core restoration is needed in an endodon- 




Fig. 6-12. Commonly seen periapical lesions. 
A, Widened periodontal ligament space. B and C, Large 
radiolucencies (established granulomas or cysts). 
(Courtesy Dr. G. Taylor.) 



tically treated tooth, 3 to 5 mm of apical seal should 
be retained (see Chapter 12). 

Performing elective endodontics may be desir- 
able in the following situations: when there are 
problems in obtaining a compatible line of draw be- 
tween multiple abutments, when it is impossible to 
gain adequate retention in a badly worn or dam- 
aged tooth, and when the endodontic prognosis of 
an abutment tooth is compromised and additional 
preparation is likely to further jeopardize its 
longevity. 



^DEFINITIVE PERIODONTAL 
TREATMENT 

Robert F. Bairn a 

Unless a patient's existing periodontal disease has 
been properly diagnosed and treated, fixed prostho- 
dontics is doomed to failure. The treatment modali- 
ties presented in Chapter 5 form the basis for an ef- 
fective approach to chronic periodontal disease. In 
addition, certain specific periodontal procedures 
may be indicated to improve the prognosis of a 
restoration. They are presented in the ensuing 
paragraphs. 

MUCOSAL REPARATIVE THERAPY 

The width of the band of attached keratinized gin- 
giva may be increased by surgical grafting as part of 
mouth preparation before restorative treatment. Al- 
though the amount of gingiva necessary for 
long-term periodontal health is open to debate and 
definite conclusions are difficult to draw, compre- 
hensive evaluation of the amount of attached 
keratinized tissue is always advised ^^ 33 n is recom- 
mended ^^^^ that a tooth to be treated with a restora- 
tion extending into the gingival sulcus should 
have approximately 5 mm of keratinized gingiva, at 
least 3 mm of which is attached gingiva. Where 
less keratinized gingiva is present, or in areas of 
localized gingival recession, a grafting or other 
gingival augmentation procedure should be con- 
sidered. 

FREE AUTOGENOUS GINGIVAL GRAFT FIG. 6-13) 
A free (detached) autogenous gingival graft is used 
to increase the width of attached gingiva in areas 
where it is deemed inadequate. The donor site most 
commonly used is the hard palate, although any 
area of keratinized tissues, such as an edentulous 
ridge or the retromolar pad, may be suitable. 

The recipient bed site is prepared by making a 
horizontal split-thickness incision just coronal to the 
mucogingival junction. As the incision passes apical 
to the junction, it may become either split thickness 



I 



Section 1 Planning and Preparation 




Fig. 6-13. Free autogenous gingival graft. A, The location of the mucogingival junction is determined 
by moving the edge of a probe coronally. B, The recipient site is prepared. C, The graft is sutured to 
place. Some apical adjustment will be needed around the premolar before application of the surgical 
dressing. D, The healed graft. (Compare the width of attached keratinized gingiva here with that in A.) 
The defective restoration can be treated at this stage. 



or full thickness. The recipient bed is trimmed of 
tissue tags and thinned. (A template of tinfoil may 
be used as a guide for the correct size and shape of 
the graft.) The graft is then carefully removed from 
the donor site, and any fat or glandular tissue is ex- 
cised, leaving a maximum thickness of 1 mm. Ster- 
ile saline is used to keep the graft moist until it is 
placed on the recipient bed for a check of size and 
shape, and it is then further shaped if necessary. 
When the proper dimensions have been attained, 
the graft is sutured into place. Finally, the graft site 
and the donor site may be covered with a surgical 
dressing. Complete healing requires approximately 
6 weeks, at which time the donor site and the 
grafted site should appear normal. 

LATERALLY POSITIONED PEDICLE GRAFT (FIG. 6-14) 

The laterally positioned pedicle graft is used for 
an area of recession or lack of attached gingiva on a 
single tooth when there are adequate amounts of 
keratinized gingiva in adjacent teeth or edentulous 
spaces. Although several studies have proposed 
techniques that use free (detached) autogenous gin- 
gival grafts for root coverage ^' 4 the pedicle graft 
can be a more predictable treatment due to mainte- 
nance of the blood supply to the pedicle. 

The recipient site is prepared by excising 1 to 3 
mm of split-thickness marginal gingiva bordering 
the recession area. At the donor site, oblique vertical 



incisions are placed in the mucosa as far apically as 
possible to ensure adequate blood supply for the 
graft. The apical area of the donor tissue is made 
wider than the coronal area. The flap is mobilized 
and placed on the recipient site and sutured into 
place. A free gingival graft may be needed to cover 
the donor site. A surgical dressing is placed over 
the site. 

There are certain limitations of laterally posi- 
tioned pedicle grafts: 

1. Some recession always occurs at the donor 
site (an average of about 1 mm) when the free 
margin of the gingiva is involved.45 

2. Severe recession is possible if the donor site 
uncovers any bony fenestration or dehis- 
cence. However, because the graft retains its 
vascularity, it may be used to cover areas of 
recession rather than just to increase the band 
of attached keratinized gingiva. Success in 
covering areas of previously denuded root 
surface may be limited, depending on the 
amount and morphology of the recession, " '' 
and the attachment between graft and root 
will often be epithelial rather than connective 
tissue. 

CORONALLY POSITIONED PEDICLE GRAFT (FIG. 6-15) 

A coronally positioned pedicle graft 48,49 is used 
when a single tooth exhibits gingival recession and 



Chapter 6 Mouth Preparation 



I 



D.E 




Fig. 6-14. Laterally positioned pedicle graft. A and B show localized recession around a mandibular 
incisor. The lateral incisor has an adequate band (width) of keratinized tissue, so it is suitable as a donor 
site. C, Bed preparation of the recipient site. An incision is made obliquely toward the site. D, Releasing 
incision at the distal of the donor site. The graft is rotated into position over the recipient site. E, Flap su- 
tured in position. A free autogenous gingival graft may be used to cover the donor site. F, The healed 
graft. There will almost always be some loss of attachment at the donor site (average 1 mm). 




Fig. 6-1 5. Coronally positioned pedicle graft. A, The position of the free gingival margin after auto- 
genous graft placement. There is approximately 4 mm of recession. B, Incisions for the pedicle. Diver- 
gence of the incisions will ensure an adequate blood supply because the base of the flap is broad. C, The 
pedicle is coronally positioned and sutured snugly to place at the CEJ with horizontal and suspension 
sutures. D, The healed graft. 

(Courtesy Dr. S.B. Ross.) 



I 



Sertion 1 Planning and Preparation 



sensitivity. If the width of the attached keratinized 
gingiva is inadequate, a free autogenous gingival 
graft may be placed to increase it before the coronal 
positioning. 

Although there are various techniques diver- 
gent vertical incisions are most commonly placed as 
far apically as possible into the mucosa. This results 
in a broader apical than coronal portion of the flap 
and ensures that the flap will have an adequate 
blood supply. The root surface is planed to a 
glasslike finish, and the graft is sutured in a coronal 
position to obtain maximum root coverage. Recent 
studies have used an alternative guided tissue re- 
generation technique to promote reattachment be- 
fore suturing the graft. 525253 ^fter the graft has been 
held in position with pressure to decrease hemor- 
rhage and to obtain proper placement, it is covered 
with a surgical dressing. 

SUBEPITHELIAL CONNECTIVE TISSUE GRAFT 

Connective tissue that does not carry epithelium 
has also been used for gingival grafting purposes. 
This technique involves the use of subepithelial 
connective tissue harvested from the palate in a 
split-thickness fashion, which allows the wound to 
be closed after removal of the graft. This approach 
minimizes patient discomfort at the donor site. 



The graft is placed at the recipient site between a 
minimally reflected split-thickness flap and the 
periosteum, covering the root. This "sandwich" 
placement of the connective tissue supplies the graft 
with blood from two different sources . 43,54 A "tun- 
nel" placement may be used as an alternative tech- 
nique, and up to 100% coverage of root recession 
has been reported. 

CROWN- LENGTHENING PROCEDURES (FIG. 6-16) 

Surgical crown lengthening or extension may be in- 
dicated to improve the appearance of an anterior 
tooth or when the clinical crown is too short to pro- 
vide adequate retention without the restoration's 
impinging on the normal soft tissue attachment 56 or 
biologic width.* This attachment averages approxi- 
mately 2 mm in width, and any restoration that im- 
pinges on it may cause bone loss because of the ef- 
fort of the host to maintain the 2 mm distance. If 
impingement occurs in an interproximal area, it can 
lead to problems with plaque control and possible 
osseous resorption. Therefore, from the stand- 



*The term biologic width refers to the combined connec- 
tive tissue-epithelial attachment from the crest of the 
alveolar bone to the base of the gingival sulcus. 34 




Fig. 6-16. Surgical crown lengthening. A, Fractured and carious second premolar. B, Reflection of a 
flap and removal of granulation tissue. C, Bone removed on the mesial to increase the distance to the 
fracture site to 3.5 mm. D, Distally the bone is removed so there will be 3.5 mm from the caries to the 
alveolar crest. E, Healing after the surgical crown lengthening. F, Final crown restoration after cementa- 
tion, before restoration of the sextant with a removable partial denture. 



Chapter 6 Mouth Preparation 



I 



point of prognosis, the biologic width should never 
be compromised. 

In some patients, an apparently hopeless tooth 
with extensive subgingival caries, a subgingival 
fracture, or root perforation resulting from en- 
dodontics can be successfully restored after crown 
lengthening. Crown lengthening increases the 
crown/root ratio, however, and a pretreatment de- 
cision must be made about whether the tooth 
should be removed or restored. 

Crown lengthening may be accomplished either 
surgically or with combined orthodontic-periodon- 
tic techniques, depending on the patient and the 
dental situation. 

Surgical Crown Lengthening (see Fig. 6-16) 
It is sometimes possible to achieve an effective in- 
crease in crown length by gingivectomy or removal 
of gingiva by electrosurgery alone, although most 
often osseous recontouring is needed to prevent en- 
croachment of the prosthesis on the biologic width. 
For these procedures, a full thickness mucoperi- 
osteal flap is reflected, and the osseous resection cre- 
ates 3.5 to 4.0 mm of space between the gingival 
crest and the margin of the existing restoration or 
carious lesion.56 65 In these instances, however, the 
following factors should be considered: 

1. Esthetics. When surgical crown lengthening 
(Fig. 6-17) is indicated, it may be difficult to 
achieve a harmonious transition from the tis 
sue around the lengthened tooth to that 
around adjacent teeth. Alternatives include 
orthodontic extrusion or removal and replace- 
ment with a prosthesis. If surgery is under- 
taken, most of the osseous reduction should 
be on the lingual or palatal side, where there 
is usually no esthetic problem, with blending 
on the labial or buccal side only as 
necessary. 



2. Root length within bone. If there is limited os- 
seous support, it may be better to remove the 
tooth and replace it with a prosthesis than to 
have the patient undergo surgery on a tooth 
with a doubtful prognosis. 

3. Effect on adjacent teeth. Often a fracture or de- 
fect will be of such depth that it cannot be 
eliminated without severely endangering the 
adjacent teeth. In these instances removal or 
orthodontic extrusion may be preferable. 

4. Root furcation exposure in a posterior tooth. If 
this situation cannot be remedied by osteo- 
plasty and/or odontoplasty, the tooth may 
require removal. 

5. Mobility. Postsurgical mobility of a tooth with 
small or conical roots is a valid concern. If 
such a tooth cannot support itself or cannot 
be supported by the adjacent teeth, then re- 
moval may be necessary. 

6. Extent of the defect. The severity and compli- 
cations of any fracture, root caries, or cervical 
wear must be carefully evaluated during the 
treatment planning phase. 

7. Root perforation. This is uncommon, but if it oc- 
curs during endodontic therapy, its location 
will determine whether to remove, orthodonti- 
cally extrude, or lengthen the tooth surgically. ^^ 

Although surgical crown lengthening may not be 
a panacea for fractured, perforated, or badly de- 
cayed teeth, it can help solve difficult and/or com- 
plex restorative problems when used with proper 
clinical judgment. 

MAINTENANCE AND RECONSTRUCTION OF THE 
I NTERDENTAL PAPILLA (FIGS. 6-1 8 TO 6-20) 

The presence or absence of the interproximal 
papilla, especially in the maxillary anterior area, is a 
concern to the restorative dentist, the periodontist, 
and the patient. Multiple techniques have been 




Fig. 6-17. Esthetic problems can occur after surgical crown lengthening of an anterior tooth. A, Lat- 
eral incisor is lengthened to include a mesial periodontal defect. B, Esthetics would have been better if 
the distal had been included and the gingival contour gradually sloped. 



I 



Se.ction 1 Planning and Preparation 

A B 




Fig. 6-1 8. Technique for surgical reproduction of the interdental papilla. A, Intrasulcular incision and 
buccal incision placed in the interdental papilla, leaving the existing papilla attached to the palatal flap. 
B, Split- thickness flap is elevated buccally and palatally. Connective tissue graft is prepared for place- 
ment under the buccal and palatal flaps. C, Buccal and palatal flaps are sutured after connective tissue 
from the retromolar area is placed under the flap. 
(From Azzi R, Etienne D, Carranza F: Int J Periodontol Rest Dent 18:467, 1998.) 



B 





Fig. 6-1 9. Reconstruction of the interdental papilla. A, Poorly contoured and bulky crowns on maxil- 
lary central incisors with loss of interdental papilla. B, Replaced crowns 1 year after cementation with 
improved tissue contours. However, interdental papilla remains in an apical position. C, Papillary inci- 
sions. D, Incisions to harvest retromolar connective tissue combined with incisions to the thin palatal 
flap. E, Connective tissue harvested in bulk. F, Connective tissue graft trimmed for placement into the 
papillary area. 
(From Azzi R, Etienne D, Carranza F: Int J Periodontol Rest Dent 18:467, 1998.) 



H 



Chapter 6 Mouth Preparation 

I 



I 





Fig. 6-1 9, cont'd. G, Connective tissue graft placed under buccal and 
palatal flaps in the interdental area. H, Flaps are sutured over connective tissue 
graft. 1, Three-day postoperative view of papillary graft. J, Final tissue contours 
around replacement crowns. 



A 




Fig. 6-20. Reconstruction of the interdental papilla. A, Preoperative view of papillary deficiency in 
the interproximal area of teeth #24 and #25. B, Results of papillary graft and final tissue contour. 

(From Azzi R, Etienne D, carranza F : Int J Perlodontol Rest Dent 18:467, 1998.) 



used, with and without the use of guided tissue or 
bone regeneration, to maintain and reconstruct the 
interdental papilla . 67-72 The results of these proce- 
dures have not been predictable or reproducible. 
The reconstruction or preservation of the papilla is 
dependent on multiple factors such as the amount 
of attachment lost in the area, the blood supply 
available for the newly created papilla,68 and the 
distance from the contact area to the crest of the in- 
terproximal bone .'3 The majority of the techniques 
used for restoration or reconstruction of the inter- 
dental papilla are surgical in nature and therefore 
involve coordination and co-therapy with surgical 
or periodontal colleagues. Consultation with the 



appropriate surgeon before planning the final 
restoration of the area is crucial. 

ORTHODONTIC-PERIODONTIC EXTRUSION (FIG. 6-21) 

Orthodontic extrusion 60,61,74 may be considered 
whenever a fracture or carious lesion extends apical 
to the free margin of the gingiva. However, it is es- 
pecially important where esthetics is a prime con- 
cern. The margin of the fracture or lesion is moved 
away from the alveolar crest orthodontically (with 
brackets, wires, and/or elastic bands), and the gin- 
giva often requires surgical repositioning when or- 
thodontic therapy is completed. 



I 



Se.ction 1 Planning and Preparation 




F,G 



Fig. 6-21. Orthodontic extrusion before restoring a badly damaged tooth. A, This maxillary first premo- 
lar has been perforated mesially (arrow). A surgical crown lengthening was contraindicated because of the 
level of the perforation apical to the osseous crest. B, A flap was reflected to debride the perforation and as- 
sociated lesion. C, Orthodontic brackets cemented with rebounding wire initially When the wire is placed in 
the premolar bracket, it will impart an occlusally directed force. (The occlusion must be relieved periodically 
as the tooth moves.) D, Completion of the extrusion. E, Osseous recontouring at this stage ensures a harmo- 
nious bony and gingival contour. F and G, Coronal tooth structure restored with a metal-ceramic crown. 
(Courtesy Dr. S.B.Ross.) 



ORTHODONTIC TREATMENT 

Minor orthodontic tooth movement can signifi- 
cantly enhance the prognosis of subsequent restora- 
tive treatment. Uprighting malpositioned abutment 
teeth can improve axial alignment, create more fa- 
vorable pontic spaces, and improve embrasure form 
in the fixed prosthesis. It can also direct occlusal 
forces along the long axes of the teeth and often 
leads to a substantial conservation of tooth structure 
(see Fig. 7-11, B,C). 

ASSESSMENT 

The clinical examination should focus on tooth mal- 
positioning both buccolingually and mesiodistally. 
Abnormal tooth relationships such as anterior or 
posterior cross bites should alert the dentist to the 
possible need for orthodontic treatment. In particu- 
lar, attempts to correct abnormal tooth relationships 



with fixed prosthodontics alone are rarely success- 
ful; orthodontic preparation is normally preferred. 
The need for orthodontic treatment is determined 
through a careful analysis of articulated diagnostic 
casts, whose usefulness can be enhanced with a den- 
tal surveyor (Fig. 6-22). One helpful procedure is to 
section a duplicate cast (Fig. 6-23) and reassemble it 
according to the proposed orthodontic modifications. 
This facilitates assessing the validity of any minor 
tooth movement (e.g., closing diastemas, uprighting 
molars, aligning tilted teeth) and is especially valu- 
able when explaining the treatment proposal to the 
patient. Diagnostic preparations and waxing proce- 
dures made on these altered casts often clearly illus- 
trate the benefits of minor tooth movement. Many 
dentists are now using computer imaging technol- 
ogy to optimize esthetic treatment planning and im- 
prove patient communication (Fig. 6-24). 




Fig. 6-22. Use of diagnostic preparations and a dental surveyor in assessing the need for orthodontic 
treatment before fixed prosthodontics. 




Fig. 6-23. Diagnostic cast sectioning for determination of desired orthodontic tooth movement. 

(Courtesy Dr. P. Ngan.) 




Fig. 6-24. Computer imaging technology can assist in treatment planning and communicating to the 
patient the esthetic changes that are envisioned. The equipment consists of a video camera, a monitor, 
and a computer. The software allows the video image to be manipulated to ascertain the post-treatment 
appearance. 

(Courtesy Envision International, Inc.) 



I 



Section 1 Planning and Preparation 



TREATMENT 

In general practice it is often possible to perform 
minor tooth movement before fixed prosthodontic 
treatment without referral to an orthodontist. How- 
ever, a specialist should be consulted if treatment is 



more complex than the straightforward tipping, up- 
righting, or extruding of an abutment tooth. 

For tipping or extruding a single anterior tooth, 
acid-etch brackets can be used with a multistrand 
elastic wire ligated in place to attain the desired po- 




E F G 

Fig. 6-25. Orthodontic tooth movement as an adjunct to fixed prosthodontics. A to C, Minor tooth 
movement before correction of a diastema. D to G, A mesially tilted molar uprighted with a coil spring 
before the provision of a fixed partial denture. (D to G courtesy Dr. P. Ngan.) 




Fig. 6-26. A, The maxillary premolar (arrow) was prepared for a metal-ceramic crown but was inade- 
quately provisionalized. Unfortunately, the patient failed to return when the provisional became dis- 
lodged. The tooth had moved distally and was in contact with the first molar, making crown placement 
impossible. B, A removable appliance was used to reposition the tooth before impression making. 
(Courtesy Dr. P. Nganj 



Chapter 6 Mouth Preparation 



I 



sition. When moving any anterior tooth, however, 
the amount of labial bone should be carefully eval- 
uated and found to be adequate. Orthodontic treat- 
ment should also be considered when restorations 
are being used to correct a diastema. Often esthetics 
can be dramatically improved by distributing the 
space of a midline diastema around all the anterior 
teeth (Fig. 6-25, A to C). A diagnostic waxing proce- 
dure will help determine the optimum tooth posi- 
tion. Uprighting a mesially tilted molar can be ac- 
compHshed with a coil spring (Fig. 6-25, D to G), but 
the tooth should first be adjusted out of occlusion. A 
neglected crown preparation can be salvaged with a 
simple orthodontic appliance (Fig. 6-26). All ortho- 
dontic movement requires adequate anchorage so 
that inadvertent movement of other teeth will be 
avoided. 



^DEFINITIVE OCCLUSAL TREATMENT 

Mouth preparation often involves reorganization of 
the patient's occlusion, typically to make intercus- 
pal position coincident with centric relation and re- 
move eccentric interferences (see Chapter 4). This 
may be done therapeutically, principally to relieve 
symptoms of occlusal dysfunction, or as a prerequi- 
site to extensive restorative treatment. The coinci- 
dence of CR and MI greatly facilitates accurately 
transferring the patient's casts to an articulator. Oc- 
clusal adjustment as a therapeutic modality is 
fraught with controversy. The current balance of re- 
search places a low priority on the influence of oc- 
clusion in disorders of the temporomandibular 
joints and associated musculature . 84 Also, there is 
clinical evidence to the contrary . However, these 
disorders should be diagnosed and alleviated be- 
fore definitive fixed prosthodontics is undertaken. 
This can generally be achieved by noninvasive, re- 
versible means. The role of occlusal forces in the 
progress of periodontal disease is also controversial. 
The balance of current research indicates that oc- 
clusal forces do not initiate periodontitis but may 
modify attachment loss caused by plaque-induced 
inflammatory periodontal disease. 89 

When selective reshaping of the natural dentition 
is being considered, it is important to remember 
that this is a purely subtractive procedure (tissue is 
removed), and it is limited by the thickness of the 
enamel. Obviously, before any irreversible changes 
are made in the dentition, a careful diagnosis must 
establish whether restorations will be needed. 

DIAGNOSTIC ADJUSTMENT 

Two sets of articulated diagnostic casts (Fig. 6-27) 
are required for diagnostic occlusal adjustment. One 
set will serve as a reference; the other will be used to 



evaluate how much tooth structure has been re- 
moved and how much more must be removed to 
meet the objectives of the procedure. This will re- 
veal the efficacy of the treatment plan before any- 
thing is done clinically. 

The occlusal surfaces of each cast are painted 
with poster paint (which will not soak into the 
stone) to demonstrate the extent of any planned cor- 
rective reshaping. The pin setting on the articulator 
is recorded before adjustment so the operator can 
judge the amount of enamel that must be removed. 
Each step of the adjustment is recorded sequentially 
on a reshaping list. When completed, the procedure 
is reviewed carefully. Areas where enamel is likely 
to be penetrated are identified so that the patient 
can be advised of the likely need for additional re- 
strictions on these teeth. 

The primary objectives of selective occlusal re- 
shaping are as follows: 

e To redistribute forces parallel to the long axes 
of the teeth by eliminating contacts on incHned 
planes and creating cusp-fossa occlusion 

• To eliminate deflective occlusal contacts: cen- 
tric relation coincides with the intercuspal po- 
sition 

• To improve worn occlusal anatomy, enhance 
cuspal shape, narrow occlusal tables, and 
reemphasize proper developmental and sup- 
plemental grooves in otherwise flat surfaces 

• To correct marginal ridge discrepancies and 
extrusions so oral hygiene will be easier 

• To correct tooth malalignment through selec- 
tive reshaping 

It will not always be possible to achieve every 
one of these goals. If a choice must be made, correc- 
tive therapy should not be at the expense of func- 
tional surfaces and should not destroy any func- 
tional contact. 




Fig. 6-27. 
casts. 



Diagnostic occlusal adjustment on articulated 



■ 



Section 1 Planning and Preparation 



CLINICAL OCCLUSAL ADJUSTMENT 

Patient Selection. Careful analysis of the diag- 1. 
nostic occlusal adjustment is necessary to determine 
whether the patient is a good candidate for such irre- 
versible subtractive treatment. Precise reduction 
and close attention to the sequence are essential. A 
written record of each reduction is also recom- 2. 
mended. If too much is ground off a tooth, it cannot 
be put back on. The following should be considered 
as contraindications to definitive occlusal adjustment: 
1- A bruxer whose habit cannot be controlled 

2. A diagnostic correction that indicates that 3. 
too much tooth structure will be removed 

3. A complex spatial relationship (e.g., an An- 
gle Class II and a skeletal Class 111) 

4. Maxillary lingual cusps contacting man- 
dibular buccal cusps 4. 

5. An open anterior occlusal relationship 

6. Excessive wear 

7. Before orthodontic or orthognathic treatment 
8- Before physical or occlusal appliance therapy 
9. A patient with temporomandibular pain 

10- A patient whose jaw movements cannot be 

manipulated easily 5. 

Occlusal adjustment needs to be undertaken in a 
logical sequence to avoid repetition and improve 
the efficacy of treatment. Although different se- 
quences have been proposed, we find the one de- 
scribed next to be successful. 6. 

Elimination of Centric Relation interferences. 

As the mandible rotates around the terminal hinge 
axis, each mandibular tooth follows its own arc of 
closure. If the intercuspal and CR positions do not 
coincide, premature contacts will be unavoidable. 



Step-by-Step Procedure 

Manipulate the mandible and mark the teeth so 
both the initial contact in centric relation and 
the extent and direction of jaw movement to in- 
tercuspation are seen. This movement, or slide, 
can be in either an anterior or a lateral direction. 
Find any interferences that cause the condylar 
processes to be displaced anteriorly (protrusive 
interferences). These will usually be between 
the mesial inclines of maxillary teeth and the 
distal inclines of mandibular teeth (Fig. 6-28). 
Continue the adjustment until all teeth contact 
evenly (except possibly the incisors). If excur- 
sive movements are guided adequately by the 
canines, it may be better to stop when bilateral 
canine-to-canine contact has been reestablished. 
When dealing with a laterally displacing pre- 
maturity, adjust the buccal-facing inclines of the 
maxillary and the lingual-facing inclines of the 
mandibular teeth. The premature contact will 
usually be on either the laterotrusive or the 
mediotrusive side of the mandible (lateral slide 
or medial slide). 

When dealing with a lateral slide, adjust the 
buccal inclines of the maxillary lingual cusps 
and the lingual inclines of the mandibular buc 
cal cusps until there is contact on the cusp tips 
(Fig. 6-29). 

When dealing with a medial slide, adjust the 
buccal inclines of the mandibular buccal cusps 
or the lingual inclines of the maxillary lingual 
cusps until there is contact on the cusp tips. At 
this time, any further adjustments can be made 
through widening of the opposing central 
grooves by reduction of the internal inclines of 



This prematurity will 
resuU m the mandibie 
sliding forward as the teeth 
come together in maximum 
inter cu spa tion (Ml). 




Fig. 6-28. interferences that dei^ect the mandible anteriorly (protrusive interferences) are found be- 
tween the mesial inclines of maxillary teeth and the distal inclines of mandibular teeth. 



Chapter 6 Mouth Preparation 



I 



the maxillary buccal and mandibular lingual 
cusps (Fig. 6-30). 

Evaluation. The foregoing rules for occlusal ad- 
justment should be followed as closely as possible 
while maintaining the normal anatomic form of the 
tooth. When the discrepancy between CR and MI 
has been corrected, there will be uniform contact be- 
tween all posterior teeth. This can be verified with 
thin Mylar shim stock held in forceps (Fig. 6-31). 

Elimination of Lateral and Protrusive Interfer- 
ences. The second phase of occlusal adjustment 
concentrates on laterotrusive, mediotrusive, and 
protrusive interferences. Use red and blue marking 




The premature contact txrcurs 
on opposing cuspal inclines 
and will cause the mandible 
to shift in the direction of the 
arrow as the teeth islide into 
their MI position. 




Fig. 6-29. Laterally displacing contact between the buc- 
cal incline of a maxillary lingual cusp and the lingual in- 
cline of a mandibular buccal cusp. 



ribbons to distinguish between centric and eccentric 
contacts. 

The goals of this second phase of adjustment are 
to eliminate contact between all posterior teeth dur- 
ing protrusive movements and to eliminate any in- 
terferences on the nonworking (mediotrusive) as 
well as the working (laterotrusive) side. In certain 
patients, group function of the working side con- 
tacts should be considered rather than the more 




B 



[ = Area of adjustment 

c 



Fig. 6-30. Correcting a medial slide by selective grind- 
ing. A, The contacting inclines are adjusted until the cusp 
tips are in contact (B). The opposing central grooves are 
then widened (C and D). 




Fig. 6-31 . Verifying occlusal contacts with thin Mylar 
shim stock. 



I 



Section 1 Planning and Preparation 



ideal mutually protected occlusion (e.g., when 
there is mobility or poor bone support of the ca- 
nines). In other patients, group function may be 
retained because of wear or malpositioning of the 
canines. 

During this phase of adjustment, it is essential 
that no centric contacts be removed. In general, lat- 
eral and protrusive interferences are eliminated by 
creating a groove that permits escape of the centric 
cusp during eccentric movement (Fig. 6-32). 



SUIWMARY 

A logical treatment sequence should be planned be- 
fore beginning any fixed prosthodontic interven- 
tion. Such planning will normally be multidiscipli- 
nary-it will incorporate oral surgery; operative 
dentistry; and endodontic, periodontic, orthodontic, 
and/or occlusal therapies. Mouth preparation is 
particularly important to fixed prosthodontics, 
which, like all dental disciplines, is facilitated and 
enhanced by meticulous preparatory treatment. 



GrcKwes on occlusal 
surfaces provide path- 
waysi for opposing 
cusps. 




Mediotrusive 



Centric cusp 



Lalerotrusive 



Fig. 6-32. Detection of eccentric interferences is facilitated by understanding where they normally oc- 
cur. The arrows represent the paths of opposing centric cusps during each excursion (mediotrusive, pro- 
trusive, and laterotrusive). Look, for example, to find a mediotrusive interference distobuccal to a centric 
contact. In the maxillary arch, the pattern is reversed. 



Sf^dy Qi^ie^iiofK 



1* Discuss in detail the recommended sequence of preparatory treatment procedures beFore initiation of de- 
finitive fixed prosthodontic treatmenL 

2p Discuss the advantages, disadvontoges, indications, and any applicable precautions for the various foun- 
dation restoration materials. 

3« Hovt/ does the tooth preparation for on extensive amalgam foundation restoration differ from a conven- 
tional extensive omafgam restorotion? Why? 

4. Discuss three types of periodontal grafting procedures, their indications, and their limitations. 

5* What are the indications for minor tooth movement before initiating fixed prosthodontic treotment? 

6« What are the indications and contraindications for comprehensive occlusal reshaping? If indicated, what 
is the recommended procedure ond sequence of events? 



Chapter 6 Mouth Preparation 



I 




awssMiij 



1 base: vt (1587): the act of placing a lining material 
under a dental restoration. 

2 base: n (14c): any substance placed under a restora- 

tion that blocks out undercuts in the preparation, 
acts as a thermal or chemical barrier to the pulp, 
and/or controls the thickness of the overlying 
restoration-called also base material-usage: ad- 
jectives such as insulating b., therapeutic b may also 
be used. 

creep: n (1818): the slow change in dimensions of an 
object due to prolonged exposure to high tempera- 
ture or stress. 

debridement: n (ca. 1842): the removal of inflamed, de- 
vitalized, contaminated tissue or foreign material 
from or adjacent to a lesion. 

deflective occlusal contact: a contact that displaces a 
tooth, diverts the mandible from its intended move- 
ment, or displaces a removable denture from its 
basal seat. 

exposure: n (1606) 1: the act of laying open, as a surgi- 
cal or dental exposure 2: in radiology, a measure of 
the roentgen rays or gamma radiation at a certain 
place based on its ability to cause ionization. The 
unit of exposure is the roentgen, called also expo- 
sure dose. 

extrusion: n (1540): the movement of teeth beyond the 
natural occlusal plane that may be accompanied by 
a similar movement of their supporting tissues. 

graft: n (14c): a tissue or material used to repair a de- 
fect or deficiency. 

maximal intercuspal position: the complete intercuspa- 
tion of the opposing teeth independent of condylar 
position, sometimes referred to as the best fit of the 
teeth regardless of the condylar position-called 
also maximal intercuspation. 

mouth guard: a resilient intraoral device useful in re- 
ducing mouth injuries and protecting the teeth and 
surrounding structures from injury. 

protrusive deflection: a continuing eccentric displace- 
ment of the midline incisal path on protrusion, 
symptomatic of a restriction of movement. 

pulp capping: application of a material to protect the 
pulp from external influences and promote healing, 
done either directly or indirectly. 



1. DeSchepper EJ et al: Clinical predictability of 
caries beneath restorations, OperDent 11:136, 
1986. 

2. Kidd EM: Caries diagnosis within restored teeth, 

OperDent 14:149, 1989. 

3. Nair MK et al: The effects of restorative material 
and location on the detection of simulated recur- 



4. 



5. 



9. 
10. 

11. 

12. 

13. 
14. 
15. 

16. 
17. 
18. 
19. 
20. 
21. 
22. 



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Schulte GA et al: Early fracture resistance of 
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DeWald JP et al: Evaluation of glass-cermet cores 
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Cohen BI et al: A five year study: fluoride re- 
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Hormati AA, Denehy GE: Microleakage of 
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Martin N, Jedynakiewicz N: Measurement of 
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Cooley RL et al: Dimensional stability of glass 
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Lambert RL, Goldfogel MH: Pin amalgam 
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thetDent5A:\0,m5. 

Outhwaite WC et al: Pin versus slot retention in 
extensive amalgam restorations, J Prosthet Dent 
41:396, 1979. 




Section 1 Planning and Preparation 



23. Shavell HM: The amalgapin technique for com- 
plex amalgam restorations, J Calif Dent Assoc 
8:48, 1980. 

24. Bailey JH: Retention design for amalgam 
restorations: pins versus slots, J Prosthet Dent 
65:71,1991. 

25. Irvin AW et al: Photoelastic analysis of stress in- 
duced from insertion of self-threading retentive 
pins, J Prosthet Dent 53:311, 1985. 

26. Felton DA et al: Pulpal response to threaded pin 
and retentive slot techniques: a pilot investiga- 
tion, J Prosthet Dent 66:597, 1991. 

27. Bonilla ED et al: A customized acrylic resin shell 
for fabricating an amalgam core on the coronally 
debilitated, endodontically treated posterior 
tooth. Quintessence 26:317, 1995. 

28. Livaditis GJ: Crown foundations with a custom 
matrix, composites, and reverse carving, J Pros- 
thet Dent 77:540, 1997. 

29. Nicholson JW, Croll TP: Glass-ionomer cements 
in restorative dentistry. Quintessence 28:705, 1997. 

30. Kerby RE, Knobloch L: Strength characteristics 
of conventional and silver-reinforced 
glass-ionomer cements, OperDent 17:170,1992. 

31. Butchart DGM, Lloyd CH: The retention of 
self-threading pins embedded in visible 
light-cured composites, J Dent 15:253, 1987. 

32. American Academy of Periodontology: Guide- 
lines for periodontal therapy, J Periodontol 69:405, 
1998. 

33. American Academy of Periodontology: Parame- 
ters of care, 1996, The American Academy of Peri- 
odontology Scientific and Educational Affairs 
Department. 

34. Maynard JG, Wilson RDK: Physiologic dimen- 
sions of the periodontium significant to the 
restorative dentist, J Periodontol 50:170, 1979. 

35. Wilson RDK, Maynard JG: Intracrevicular 
restorative dentistry, Int J Periodont Rest Dent 
1:34,1981. 

36. Sullivan HC, Atkins JH: Free autogenous gingi- 
val grafts. I. Principles of successful grafting. 
Periodontics 6:121, 1968. 

37. Dordick B et al: Clinical evaluation of free auto- 
genous gingival grafts placed on alveolar bone. 
1. Clinical predictability, J Periodontol 47:559, 
1976. 

38. Oliver RC et al: Microscopic evaluation of the 
healing and revascularization of free gingival 
grafts, i Periodontol Res 3:84, 1968. 

39. Staffileno H Jr, Levy S: Histological and clinical 
study of mucosal (gingival) transplants in dogs, 
J Periodontol 40:311, 1969. 

40. Grupe HE, Warren RE: Repair of gingival defects 
by a sliding flap operation, J Periodontol 29:92, 
1956. 



41. Bjorn H: Coverage of denuded root surfaces 
with a lateral sliding flap: use of free gingival 
grafts, OdontolRev 22:37, 1971. 

42. Holbrook T, Ochsenbien C: Complete coverage 
of the denuded root surface with a one- stage 
gingival graft, Int ] Periodont Rest Dent 3:9, 1983. 

43. Miller PD Jr: Root coverage using the free soft 
tissue autograft following citric acid application. 
III. A successful and predictable procedure in ar- 
eas of deep wide recession, Int J Periodont Rest 
Dent 5:15, 1985. 

44. Raetzke PB: Covering localized areas of root ex- 
posure employing the "envelope" technique, 

J Periodontol 56:397, 1985. 

45. Caffesse RG, Guinard EA: Treatment of localized 
gingival recessions. IV Results after three years, 
] Periodontol 51:167, 1980. 

46. Sullivan HC, Atkins JH: Eree autogenous gingi- 
val grafts. III. Utilization of grafts in the treat- 
ment of gingival recession. Periodontics 6:152, 
1968. 

47. Miller PD Jr: A classification of marginal tissue 
recession, Int J Periodont Rest Dent 5:9, 1985. 

48. Bernimoulin JP et al: Coronally repositioned pe- 
riodontal flap: clinical evaluation after one year, 
J Clin Periodontol 2:1, 1975. 

49. Maynard JG: Coronal positioning of a previ- 
ously placed autogenous gingival graft, J Peri- 
odontol 4^:151, 1977. 

50. Tarnow DP: Semilunar coronally repositioned 
flap, J Clin Periodontol 13:182, 1986. 

51. Allen EP, Miller PD Jr: Coronal positioning of 
existing gingiva: short-term results in the treat- 
ment of shallow marginal tissue recession, J Peri- 
odontol 60:316, 1989. 

52. Pini Prato GP et al: Guided tissue regeneration 
versus mucogingival surgery in the treatment of 
human buccal recessions, J Periodontol 67:1216, 
1996. 

53. Matarasso MD et al: Guided tissue regeneration 
versus coronally repositioned flap in the treat- 
ment of recession with double papillae, Int J 
Periodontol Rest Dent 18:445, 1998. 

54. Langer B, Langer L: Subepithelial connective tis- 
sue graft technique for root coverage, J Periodon- 
tal 56:115, 19S5. 

55. Zabalegui I et al : Treatment of multiple gingival 
recessions with the tunnel subepithelial connec- 
tive tissue graft: a clinical report, Int J Periodontal 
Rest Dent 19:199, 1999. 

56. Davarpanah M et al: Restorative and periodon- 
tal considerations of short clinical crowns, Int J 
Periodontol Rest Dent 18:5,1998. 

57. Palomo E, Kopczyk RA: Rationale and methods 
for crown lengthening, J Am Dent Assoc 96:257, 
1978. 



Chapter 6. Month Prerparation 



I 



58. 

59. 
60. 



61. 



62. 



63. 



64. 



65. 



66. 



67. 



69. 



70. 



71. 



72. 



73. 



74. 



Ochsenbien C, Ross SE: A reevaluation of os- 75. 

seous surgery, Dent Clin North Am 13:87,1969. 
Maynard JG: Personal communication, 1993. 
Ross SB et al: Orthodontic extrusion: a multidis- 76. 
ciplinary treatment approach, ] Am Dent Assoc 
102:189,1981. 

Brown IS: The effect of orthodontic therapy on 77. 

certain types of periodontal defects: clinical find- 
ings, J Penodontol 44:742, 1973. 

Ingber JS: Forced eruption. I. A method of treat- 78. 
ing isolated one and two wall infrabonyosseous 
defects: rationale and case report, J Penodontol 
45:199,1974. 79. 

Delivanis P et al: Endodontic-orthodontic man- 
agement of fractured anterior teeth, J A m Dent 80. 
A550C 97:483, 1978. 

Potashnik SR, Rosenberg ES: Forced eruption: 
principles in periodontics and restorative den- 81. 

tistry, J ProsthetDent 48:141, 1982. 
Baima RF: Extension of chnical crown length, 
J Prosthet Dent 55:547,1986. 82. 

Rosenberg ES et al: Tooth lengthening proce- 
dures, Compend Contin Educ Dent 1:11, 1980. 83. 
Shapiro A: Regeneration of interdental papilla 

using periodic curettage, Int J Periodont Rest Dent 

5:27, 1985. 84. 

Evian C, Corn H, Rosenberg E: Retained inter- 
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Han TJ, Takei HH: Progress in gingival papilla 85. 

reconstruction, Penodontol 2000 11:65, 1996. 
Cortellini P, Pini Prato G, Tonetti MS: The modi- 
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sorbable barrier membranes in the treatment of 

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Beagle JR: Surgical reconstruction of the inter- 
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Tamow DP, Magner AW, Fletcher P: The effect of 
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Johnson GK, Sivers JE: Forced eruption in 
crown-lengthening procedures, J Prosthet Dent 
56:424, 1986. 



Tuncay OC: Orthodontic tooth movement as an 
adjunct to prosthetic therapy, J Prosthet Dent 
46:41, 1981. 

Miller TE: Orthodontic therapy for the restora- 
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42:285,1998. 



A 




Principles of Tooth Preparation 



causes of injury 
conservation of toothi structure 
diagnostic preparations 
margin designs 
margin placement 



pathi of insertion 

resistance 

retention 

taper 

undercut 



Teeth do not possess the regenerative abihty found in 
most other tissues. Therefore, once enamel or dentin 
is lost as a result of caries, trauma, or wear, restora- 
tive materials must be used to reestablish form and 
function. Teeth require preparation to receive restora- 
tions, and these preparations must be based on fun- 
damental principles from which basic criteria can be 
developed to help predict the success of prosthodon- 
tic treatment. Careful attention to every detail is im- 
perative during tooth preparation. A good prepara- 
tion will ensure that subsequent techniques (e.g., 
provisionalization, impression making, pouring of 
dies and casts, waxing) can be accomplished. 

The principles of tooth preparation may be di- 
vided into three broad categories: 

1. Biologic considerations, which affect the 
health of the oral tissues 

2. Mechanical considerations, which affect the 
integrity and durability of the restoration 

3. Esthetic considerations, which affect the ap- 
pearance of the patient 

Successful tooth preparation and subsequent 
restoration depend on simultaneous consideration of 
all these factors. Often improvement in one area will 
adversely affect another, and striving for perfection 
in one may lead to failure in another. For example, in 
the fabrication of a metal-ceramic crown (see Chapter 
24), sufficient thickness of porcelain is necessary for a 
lifeliice appearance. However, if too much tooth 
structure is removed to accommodate a greater thick- 
ness of porcelain for esthetic reasons, the pulpal tis- 
sue may be damaged (biologic consideration) and 
the tooth unduly weakened (mechanical considera- 
tion). An in-depth knowledge and understanding 
of the various criteria are prerequisites to the devel- 
opment of satisfactory tooth preparation skills. 
Predictable accomplishment of optimum tooth 
preparation (Fig. 7-1) often entails finding the best 




Fig. 7- 1 . The optimum restoration should satisfy bio- 
logic, mechanical, and esthetic requirements. 



combination of compromises among the prevalent 
biologic, mechanical, and esthetic considerations. 

BIOLOGIC CONSIDERATIONS 

Surgical procedures involving living tissues must 
be carefully executed to avoid unnecessary damage. 
The adjacent teeth, soft tissues, and the pulp of the 
tooth being prepared are easily damaged in tooth 
preparation. If poor preparation leads to inadequate 
marginal fit or deficient crown contour, plaque con- 
trol around fixed restorations will become more dif- 
ficult. This will impede the long-term maintenance 
of dental health. 

PREVENTION OF DAMAGE DURING 
TOOTH PREPARATION 

Adjacent Teeth. Iatrogenic damage to an adja- 
cent tooth is a common error in dentistry. Even if a 
damaged proximal contact area is carefully re- 
shaped and polished, it will be more susceptible to 
dental caries than the original undamaged tooth 



166 



Chapter 7 Principles of Tooth Preparati on 



I 



surface. This is presumably because the original 
surface enamel contains higher fluoride concentra- 
tions and the interrupted layer is more prone to 
plaque retention. The technique of tooth prepara- 
tion must avoid and prevent damage to the adjacent 
tooth surfaces. 

A metal matrix band around the adjacent tooth 
for protection may be helpful; however, the thin 
band can still be perforated and the underlying 
enamel damaged. The preferred method is to use 
the proximal enamel of the tooth being prepared for 
protection of the adjacent structures. Teeth are 1.5 to 
2 mm wider at the contact area than at the cemen- 
toenamel junction (CEJ), and a thin, tapered dia- 
mond can be passed through the interproximal con- 
tact area (Fig. 7-2) to leave a slight lip or fin of 
enamel without causing excessive tooth reduction 
or undesirable angulation of the rotary instrument. 

Soft Tissues. Damage to the soft tissues of the 
tongue and cheeks can be prevented by careful re- 
traction with an aspirator tip, mouth mirror (Fig. 
7-3), or flanged saliva ejector. Great care is needed to 
protect the tongue when the lingual surfaces of 
mandibular molars are being prepared. 

Pulp. Great care also is needed to prevent pul- 
pal injuries during fixed prosthodontic procedures, 




especially complete crown preparation. Pulpal de- 
generation that occurs many years after tooth 
preparation has been documented.' Extreme tem- 
peratures, chemical irritation, or microorganisms 
can cause an irreversible pulpitis, particularly 
when they occur on freshly sectioned dentinal 
tubules. Prevention of pulpal damage necessitates 
selection of techniques and materials that will re- 
duce the risk of damage while preparing tooth 
structure. 

Tooth preparations must take into consideration 
the morphology of the dental pulp chamber. Pulp 
size, which can be evaluated on a radiograph, de- 
creases with age. Average pulp dimensions have 
been related to coronal contour 4 and are presented 
in Table 7-1 and Figure 7-4. 

Causes of Injury 

Temperature. Considerable heat is generated by 
friction between a rotary instrument and the surface 
being prepared (Fig. 7-5). Excessive pressure, higher 
rotational speeds, and the type, shape, and condition 
of the cutting instrument (Fig. 7-6) may all increase 
generated heat.' With a high-speed handpiece, a 
feather-light touch allows efficient removal of tooth 
material with minimal heat generation. Nevertheless, 
even with the lightest touch, the tooth will be over- 
heated unless a water spray is used. This must be ac- 
curately directed at the area of contact between tooth 
and bur. It will also remove debris (important be- 
cause clogging reduces cutting efficiency) and pre- 
vent desiccation of the dentin (a cause of severe pul- 
pal irritation' 6). If the spray prevents adequate 
visibility, as may be the case when finishing a Ungual 
margin, a slow- speed handpiece or hand instrumen- 
tation should be used. Relying on air cooling with a 
high-speed handpiece is hazardous, because it can 
easily overheat a tooth and damage the pulp.' 




Fig. 7-2. Damage to adjacent teeth is prevented by mak- 
ing a thin "lip" of enamel as the bur passes through a prox- 
imal contact. 



Fig. 7-3. Mouth mirror protecting the soft tissues during 
tooth preparation. 



►ronai con 



Age Range Coronal Length 
(yr) (mm) 



10-19 
20-29 
30-39 
40-49 
50-59 
Mean 
±SD 
Ranqe 



12.1 

11,5 
11.2 
10.8 
12.3 

IK58±0.34 
9.70-14,00 



10-19 

20-29 

30-39 

40-49 

50-59 

Mean 

±SD 

Range 



Age Range 



10-19 
20-29 
30-39 
40-49 
50-59 
Mean 
±SD 
Range 



10,1 
10,2 
10.0 

9.0 

9.7 

8-84 ± 0.23 
7.90-11.91 



Incisal to 

MPH 

(mm) 



4,7 
4,8 
5.3 
6.3 
6,3 

5.5 ± 0.25 
4,0-6.2 



Incisal to 
Age Range Coronal Length MPH 

(y) (mm) (mm) 



Coronal Length 
(mm) 



107 
10.6 
10-5 

9.5 

9.9 

10.23-0.26 
8,29-12.20 



Incbal to 
DPH 



4.B 
5.1 
5.5 
6,1 
62 

5.6 ± 0,28 
4,0-6.2 



Incisal to 
DPH 
(mm) 



Maxillary Central Incisor 
Mesial Distal 

Surface to Surface to 

MPH DPH 



1.7 
2.2 
2.1 
2.5 
2.6 

2.2 ±0.16 

1.2-3.3 



2.1 
2.3 
2,5 
2.9 
24 

2.5 ± 0.14 
1 .4-3.5 



Maxillary Lateral Incisor 

Mesial Distal 

Surface to Surface to 

MPH DPH 

(mm) (mm) 



3,9 


4,3 


2.4 


2.6 


4.8 


5.2 


2.5 


3,2 


4.8 


— 


2.4 


3.2 


4.8 


5.2 


1.9 


2.2 


6.0 


— 


2.2 


2.3 


4.9 ± 0.40 


4,9 ± 0.32 


2.3-0.20 2,7 ±0.19 


3,6-6.2 


3.6-6.4 


1.2-3.2 1.8-3.6 






Maxillary Canine 








Mesial 








Surface to 


h 


Incisal to PH 




PH 




(mm) 




(mm) 




4.4 




3-4 




4,6 




3.3 




4,8 




3.0 




4,8 




3.0 




5,4 




2:8 




4.8 ± 0.20 




3.1 ±0.13 




3,8-1.2 




2.3-3.6 



Labial 

Surface to 

MPH 

(mm) 



1.8 
\S 
2.3 

2.0 
2.8 

2.2 ±0.12 
1.5-2.9 



Labial 

Surface to 

MPH 

(mm) 



2.0 
2.4 

2.1 
2.1 
2.3 

2.2 ± 0.04 
1 .7-2.7 



Distal Surface 
to PH 
(mm) 



4.0 
3.7 
4.0 
3.6 
3.4 

3.7 ±0.12 
2.9-4.8 



Labial 

Surface to 

DPH 

(mm) 



1.9 
2.4 
2.1 
2.3 

2.1 ±0.12 
1.5-2.9 



Labial 

Surface to 
DPH 
(mm) 



2.1 
2.4 
2.3 
2.1 
2.3 

2.2 ±0.15 
1.8-2.7 



Palatal 

Surface to 

MPH 

(mm) 



1.4 
1.4 
2.1 
2.0 
2.2 

1.8 ±0.16 
1.0-2.9 



Palatal 

Surface to 
MPH 
(mm) 



L3 
1.9 
2.0 
1.7 
2.6 

1.9±0.11 
1.2-3.2 



Labial 

Surface to 

PH 

(mm) 



2.7 
3.1 
2.9 
2.8 
2.9 

2.9 ±0.11 
2.5-3.5 



TABLE 7-1 



Palatal 

Surface to 

DPH 

(mm) 



13 
1.2 
2.0 

1,8 
2.1 

l.7±0.19 
1.1 2.9 



Palatal 

Surface to 

DPH 

(mm) 



1.3 
1.9 
1.7 
1.5 
2.5 

1.8 ±0.17 
1.1-2,9 



Palatal 

Surface to 

PH 

(mm) 



2.3 
2.6 
2,5 
2,8 
3,0 

2.6 ±0.15 
1.9-3.7 



From Ohashi Y: Sliika^iakuho 68726. 1968. 

MPH, Mesial pulp horn; DPH, distal pulp hum; PH, pulp horn. 



ft 
o 



Chapter 7 Prin <:^£S of Toofh Prpparafion 



I 



50-59 




30-39 
20-29 

10-19 
years 



50-59 

40-49 
30-39 
20-29 

10-19 
years 



Fig. 7-4. Relationship between tooth preparation and 
pulp chamber size. The dotted Hnes represent pulp cham- 
ber morphology at various ages. A, Maxillary central in- 
cisor with a metal-ceramic crown preparation. B, Maxillary 
lateral incisor with a metal-ceramic crown preparation. 
C, Maxillary canine with a pinledge preparation. 
(FromOhashiY: Shikagakuho 68:726,1968.) 



Sttirting fevel q 




Critical 

ranjse 



Group I 



Safe 
range 





A 

Bur 

contact 



5 20 15 20 25 
Tooth contact (sec) 



30 35 



Fig. 7-5. Pulpal temperature rise during tooth prepara- 
tion. Group /, air turbine, water cooled. Group //, air tur- 
bine, dry. Group ///, low speed, water cooled. Group IV, 
low speed, dry. 
(From ZachL, Cohen G: Oral Surg 19:515,1965.) 



Particular care is needed when preparing 
grooves or pinholes, because coolant cannot reach 
the cutting edge of the bur. To prevent heat buildup, 
these retention features should always be prepared 
at low rotational speed. 

Chemical Action. The chemical action of cer- 
tain dental materials (bases, restorative resins, sol- 
vents, and luting agents) can cause pulpal damage," 
particularly when they are applied to freshly cut 
dentin. Cavity varnish or dentin bonding agents 
will form an effective barrier in most instances, but 
their effect on the retention of a cemented restora- 
tion is controversial. 

Chemical agents are sometimes used for cleaning 
and degreasing tooth preparations. However, they 
have been shown to be pulpal irritants. Thus their 
use is generally contraindicated, particularly be- 
cause they do not improve the retention of ce- 
mented restorations. ^^ 

Bacterial Action. Pulpal damage under restora- 
tions has been attributed ^^ ^^ to bacteria that either 
were left behind or gained access to the dentin be- 
cause of microleakage. However, many dental mate- 
rials, including zinc phosphate cement, have an an- 
tibacterial effect ; because vital dentin seems to resist 
infection," the routine use of antimicrobials may not 
be advantageous. Many dentists now use an antimi- 
crobial agent, such as Consepsis,* after tooth 



*Ultradent Products, Inc. 



I 



Section 2 Clinical Procedures-Part I 




rig. /-b. Scanning electron micrographs of a rotary instrument. A, Unused diamond. B, Unused car- 
bide. C, Worn diamond. D, Diamond particles have fractured at the level of the binder. 
(Courtesy Dr. J.L. Sandrik.) 




rig. / - / . A considerable amount of care is needed when 
preparing a tooth for a complete crown because of the ex- 
tensive nature of the reduction, with many dentinal tubules 

sectioned. Each tubule communicates directly with the den- 
tal pulp. 



preparation and before cementation, although the 
benefit has not been documented in clinical trials. 18 
NOTE: All carious dentin should be removed be- 
fore placing a restoration that will serve as a foun- 
dation for a fixed prosthesis. An indirect pulp cap is 
not recommended, because its later failure is likely 
to jeopardize extensive prosthodontic treatment. 

CONSERVATION OF TOOTH STRUCTURE 

One of the basic tenets of restorative dentistry is to 
conserve as much tooth structure as possible consis- 
tent with the mechanical and esthetic principles of 
tooth preparation. This will reduce the harmful pul- 
pal effects of the various procedures and materials 
used. The thickness of remaining dentin has been 
shown" to be inversely proportional to the pulpal 
response, and tooth preparations extending deeply 
toward the pulp should be avoided. Dowden20 has 
argued that any damage to the odontoblastic 
processes will adversely affect the cell nucleus at the 
dentin-pulp interface, no matter how far from the 
nucleus it occurs. For this reason, when assessing 
likely adverse pulpal response, the amount of 
dentin removed is important; particular care must 
be exercised when preparing vital teeth for com- 
plete-coverage restorations (Fig. 7-7). 

Tooth structure is conserved by using the follow- 
ing guidelines: 

1. Use of partial-coverage rather than complete- 
coverage restorations (Fig. 7-8) 



Chapter 7 Principles of Tooth Preparation 



I 




Fig. 7-8. Conservation of tooth structure by 
using partial-coverage restorations. In this case, 
they are used as FPD abutments to replace con- 
genitally missing lateral incisors. 



2. Preparation of teeth with the minimum prac- 
tical convergence angle (taper) between axial 
walls (Fig. 7-9) 

3. Preparation of the occlusal surface so reduc- 
tion follows the anatomic planes to give uni- 
form thickness in the restoration (Fig. 7-10) 

4. Preparation of the axial surfaces so tooth 
structure is removed evenly; if necessary, 
teeth should be orthodontically repositioned 
(Fig. 7-11) 

5. Selection of a conservative margin compati- 
ble with the other principles of tooth prepa- 
ration (Fig. 7-12) 

6. Avoidance of unnecessary apical extension of 
the preparation (Fig. 7-13) 

CONSIDERATIONS AFFECTING FUTURE DENTAL HEALTH 

An improperly prepared tooth may have an adverse 
effect on long-term dental health. For example, in- 
sufficient axial reduction inevitably results in an 
overcontoured restoration that hampers plaque 
control. This may cause periodontal disease or 
dental caries. Alternatively, inadequate occlusal re- 
duction may result in occlusal dysfunction, and 
poor margin placement may lead to chipped 
enamel or cusp fracture. 

Axial Reduction. Gingival inflammation is 
commonly associated with crowns and FPD abut- 
ments having excessive axial contours, probably be- 
cause it is more difficult for the patient to maintain 
plaque control around the gingival margin. A 
tooth preparation must provide sufficient space for 




Fig. 7-9. Excessive taper results in considerable loss of 

tooth structure (shaded area). 




Minimally required clearances: 

Buccal cusp — 15 mm 

Lingual cusp—LO mm 

Marginal ridges and fos!>ae — 1.0 mm 



Fig. 7-1 0. An anatomically prepared occlusal surface re- 
sults in adequate clearance without excessive tooth reduc- 
tion. A flat occlusal preparation will result in either (1) in- 
sufficient clearance or (2) an excessive amount of reduction. 



I 



Section 2 Clinical Procedures-Part I 



B 




Fig. 7-11 . To conserve tooth structure, the preparation of axial 
surfaces should be as uniform as possible. A, The path of withdrawal 
should coincide with the long axis of the tooth, which for a mandibu- 
lar premolar is typically inclined 9 degrees lingually. Preparing the 
tooth perpendicular to the occlusal plane is a commonly seen error 
and results in additional tooth reduction (shaded area). B and C, Tooth 
structure is conserved by uprighting a tilted FPD abutment. 



OTi^ 




Fig. 7-12. A shoulder margin (2) is less conservative 
than a chamfer (1). 




Fig . 7-13 . A, Apical extension of the preparation can necessi- 
tate additional tooth reduction. B, Preparations for periodontally 
involved teeth may necessitate considerable reduction if the 
margins are to be placed subgingivally for esthetic reasons. 
C, Supragingival margins are preferred where applicable. 




Chapter 7 Principles of Tooth Preparation 



I 



the development of good axial contours. This will 
enable the junction between the restoration and the 
tooth to be smooth and free of any ledges or abrupt 
changes in direction. 

Under most circumstances a crown should dupli- 
cate the contours and profile of the original tooth 
(unless the restoration is needed to correct a mal- 
formed or malpositioned tooth). If an error is made, 
a slightly undercontoured flat restoration is better 
because it is easier to keep free of plaque; however, 
increasing proximal contour on anterior crowns to 
maintain the interproximal papilla" (see Chapter 5) 
may be beneficial. Sufficient tooth structure must be 
removed to allow the development of correctly 
formed axial contours (Fig. 7-14), particularly in the 
interproximal and furcation areas of posterior teeth, 
where periodontal disease often begins. 

Margin Placement. Whenever possible, the 
margin of the preparation should be supragingival. 
Subgingival margins of cemented restorations have 
been identified as a major factor in periodontal 
disease, particularly where they encroach on the ep- 



ithelial attachment (see Chapter 5). Supragingival 
margins are easier to prepare accurately without 
trauma to the soft tissues. They can usually also be 
situated on hard enamel, whereas subgingival mar- 
gins are often on dentin or cementum. 

Other advantages of supragingival margins in- 
clude the following: 

1. They can be easily finished. 

2. They are more easily kept clean. 

3. Impressions are more easily made, with less 
potential for soft tissue damage. 

4. Restorations can be easily evaluated at recall 
appointments. 

However, a subgingival margin (Fig. 7-15) is jus- 
tified if any of the following pertain: 

1. Dental caries, cervical erosion, or restorations 
extend subgingivally, and a crown-lengthen- 
ing procedure (see Chapter 6) is not indicated. 

2. The proximal contact area extends to the gin- 
gival crest. 

3. Additional retention is needed. 

4. The margin of a metal-ceramic crown is to be 
hidden behind the labiogingival crest. 




Fig. 7-14. A and B, Tooth preparations with adequate axial reduction allow the development of prop- 
erly contoured embrasures. Tissue is conserved by using partial coverage and supragingival margins 
where possible. C, Preparing furcation areas adequately is important; otherwise, the restoration will be 
excessively contoured, making plaque control difficult. 



I 



Section 2 Clinical Procedures-Part I 




Fig. 7-15. Examples where subgingival margins are indicated. A, To include an existing restoration. 
B, To extend apical to the proximal contact (adequate proximal clearance). C and D, To hide the metal 
collar of metal- ceramic crowns. 



5. Root sensitivity cannot be controlled by more 
conservative procedures, such as the applica- 
tion of dentin bonding agents. 

6. Modification of the axial contour is indicated. 

Margin Adaptation. The junction between a ce- 
mented restoration and the tooth is always a poten- 
tial site for recurrent caries because of dissolution of 
the luting agent and inherent roughness. The more 
accurately the restoration is adapted to the tooth, 
the lesser the chance of recurrent caries or peri- 
odontal disease . 3° Although a precise figure for ac- 
ceptable margin adaptation is not available, a 
skilled technician can make a casting that fits to 
within 10 u and a porcelain margin that fits to 
within 50 um, provided the tooth is properly pre- 
pared. A well-designed preparation has a smooth 
and even margin. Rough, irregular, or "stepped" 
junctions greatly increase the length of the margin 
and substantially reduce the adaptation of the 
restoration (Fig. 7-16). The importance of preparing 
smooth margins cannot be overemphasized. Time 
spent obtaining a smooth margin will make the sub- 
sequent steps of tissue displacement, impression 
making, die formation, waxing, and finishing much 
easier and will ultimately provide the patient with a 
longer-lasting restoration. 



Margin Geometry. The cross-sectional configu- 
ration of the margin has been the subject of much 
analysis and debate .33 Different shapes have been 
described and advocated ^^ ^^ por evaluation, the 
following guidelines for margin design should be 
considered: 

1. Ease of preparation without overextension or 
unsupported enamel 

2. Ease of identification in the impression and on 
the die 

3. A distinct boundary to which the wax pattern 
can be finished 

4. Sufficient bulk of material (to enable the wax 
pattern to be handled without distortion and to 
give the restoration strength and, when porce- 
lain is used, esthetics) 

5. Conservation of tooth structure (provided the 
other criteria are met) 

Proposed margin designs are presented in Ta- 
ble 7-2. 

Although they are conservative of tooth struc- 
ture, featheredge or shoulderless crown prepara- 
tions (Fig. 7-17, A) should be avoided because they 
fail to provide adequate bulk at the margins. Over- 
contoured restorations often result from feath- 
eredge margins because the technician can handle 
the wax pattem without distortion only by increas- 



Chapter 7 Principles of Tooth Preparation 



I 




A smooth margin is 
considerably shorter 
than a jagged one- 





R 



Fig. 7-16. A and B, Poor preparation design, leading to increased margin length. C, A rough, irregu- 
lar margin will make the fabrication of an accurately fitted restoration almost impossible. D, An accu- 
rately fitting margin is possible only if it is prepared smoothly. 



Advantages 



s of Different Margin D 

Disadvantages 



JAB LE 7-2 



Conservative of tooth structure 
Conservative of tooth structure 

Bevel Removes unsupported enamel, 

allows finishing of meto! 

Chamfer DisHnct margin, adequate bulk, 

easier to controi 
Shoutder Bulk of restorative materioi 

Sloped Bulk of material, advantages of 

shoulder bevel 

Shoulder with Bulk of material, advantages of 

bevel bevel 



Does not provide sufficient bulk 
Location of margin difficult to 

control 
Extends preparation into sulcus if 

used on apical margin 

Care needed to ovoid unsup- 
ported lip of enamel 

Less conservative of tooth 
structure 

Less conservative of too^b 
structure 

Less conservative, extends 
preparation apically 



Indications 



Nol recommended 
Occasionally on tilted teeHi 

Facial margin of maxiliory partial- 
coverage restorations and 
inlay/on by margins 

Cast metal restorations, linguoi 
margin of metal-ceramic crowns 

Facial margin of metal-ceramic 
crowns, complete ceramic crowns 

Facial margins of metal ceramic 
crowns 

Facial margin of posterior metoi- 
ceramic crowns with supragingi- 
val margins 



ing its bulk beyond the original contours. A varia- 
tion of the featheredge, the chisel edge margin (Fig. 
7-17, B), is formed when there is a larger angle be- 
tween the axial surfaces and the unprepared tooth 
structure. Unfortunately, this margin is frequently 
associated with an excessively tapered preparation 
or one in which the axial reduction is not correctly 
aligned with the long axis of the tooth. 



Under most circumstances, featheredges and 
chisel edges are unacceptable. Historically their 
main advantage was that they facilitated the mak- 
ing of impressions with rigid modeling compound 
in copper bands (a technique rarely used today), be- 
cause there was no ledge on which a band could 
catch. A chamfer margin (Fig. 7-17, C ) is particu- 
larly suitable for cast metal crowns and the 



I 



Section 2 Clinical Procedures-Part I 

A i C D 




M 



Fig. 7-17. Margin designs: A, Featheredge. B, Chisel. C, Chamfer. D, Bevel. E, Shoulder. F, Sloped 
shoulder. G, Beveled shoulder. Scanning electron micrographs. H, Feather-chisel edge. I, Chamfer. 
J, Bevel. K, Shoulder. L, Sloped shoulder. M, Beveled shoulder. 
(Courtesy Dr. H. Lin.) 



metal-only portion of metal- ceramic crowns (Fig. 
7-18). It is distinct and easily identified, provides 
room for adequate bulk of material, and can be 
placed with precision, although care is needed to 
avoid leaving a ledge of unsupported enamel. 

Probably the most suitable instrument for mak- 
ing a chamfer margin is the tapered diamond with a 
rounded tip; the margin formed is the exact image 
of the instrument (Fig. 7-19). Marginal accuracy de- 
pends on having a high-quality diamond and a 
true-running handpiece. The gingival margin is pre- 
pared with the diamond held precisely in the in- 



tended path of withdrawal of the restoration (Fig. 
7-20). Tilting it away from the tooth will create an 
undercut, whereas angling it toward the tooth will 
lead to overreduction and loss of retention. The 
chamfer should never be prepared wider than half 
the tip of the diamond; otherwise, an unsupported 
lip of enamel could result (Fig. 7-21). Some authori- 
ties have recommended the use of a diamond with 
a noncutting guide tip to aid accurate chamfer 
placement. " However, the guide has been shown to 
damage tooth structure beyond the intended prepa- 
ration margin .44 



Chapter 7 Principles; of Tooth Preparation 



I 




laiiv ,ieikx ie»F 883 



tsitv .e^tkK ss^i* **• 




Fig. 7-18. Chamfer margins are recommended for cast metal crowns (A) and the lingual margin of a 
metal-ceramic crown (B). Compare the scanning electron micrographs of a chamfer (C) achieved with a 
fine-grit diamond after initial preparation with a coarser instrument (D) and a chamfer achieved with 
finishing carbides (E and F). 
(C to F courtesy Dr. H. Lin.) 

Under some circumstances a beveled margin (Fig. 
7-17, D) is more suitable for cast restorations, partic- 
ularly if a ledge or shoulder already exists, possibly 
from dental caries, cervical erosion, or a previous 
restoration. The objective in beveling is threefold: 
(1) to allow the cast metal margin to be bent or bur- 
nished against the prepared tooth structure; (2) to 
minimize the marginal discrepancy 33 caused by a 
complete crown that fails to seat completely (how- 
ever, Pascoe has shown that when an oversized 
crown is considered, the discrepancy is increased 
rather than decreased [Fig. 7-22]); and (3) to protect 
the unprepared tooth structure from chipping (e.g., 
by removing unsupported enamel). NOTE: When Pig ^.^ g ^ ^^^^^^^ ^^^^-^ -^ 

access for burnishing is limited, there is little ad- ^ \ formed as the negative image of a 

vantage in beveling. This applies particularly to a - : round-ended tapered diamond. 




I 



Section 2 Clinical Procedures-Part I 





«t left, the diamond is tipped away 
from the path of placement, resulting 
in an undercut; at right, the diamond 
is tipped into the tooth too far, leading 
to an excessively tapered preparation. 



Fig. 7-20. Precise control of the orientation of the diamond is very important. A, Tilting away from 
the tooth creates an undercut. B, Tilting toward the tooth results in excessive convergence. 




All unsupported 
enamel must he 
removed. 



Fig. 7-21 . A chamfer should not be wider than half the 
bur used to form it. Otherwise, a lip of unsupported 
enamel will be left. 



gingival margin, where beveling would lead to sub- 
gingival extension of the preparation or placement 
of the margin on dentin rather than on enamel. Fa- 
cial margins of maxillary partial-coverage restora- 
tions should be beveled to protect the remaining 
tooth structure and to allow for burnishing. 

Because a shoulder margin (Fig. 7-17, E) allows 
room for porcelain, it is recommended for the facial 
part of metal-ceramic crowns, especially when the 
porcelain margin technique is used. It should form 
a 90-degree angle with the unprepared tooth sur- 
face. An acute angle is likely to chip (Fig. 7-23, A). In 
practice, dentists tend to underprepare the facial 
shoulder, leading to restorations with inferior es- 
thetics or poor axial contour. 

Some authorities46 have recommended a heavy 
chamfer rather than a shoulder margin, and some 




shoulder 



45° Bevel 



ffy(3 



Properly seated castings 
should have minimal 
marginal gap widtlis. 



Fig. 7-22. Effect on marginal fit of beveling the gingival 
margin. A, If the internal cross section of a crown is the 
same as or less than that of the prepared tooth, a 45-degree 
bevel will decrease the marginal discrepancy by 70%. B, If 
the internal diameter is slightly larger than the prepared 
tooth, beveling will increase the marginal discrepancy. In 
practice, crowns are made slightly larger than the prepared 
tooth to allow for the luting agent. 



find a chamfer easier to prepare with precision. Ear- 
lier work '^^^ found less distortion of the metal 
framework during porcelain application, although 
with modern alloys, this doesn't appear to be a 
problem (see Chapter 19). 



Chapter 7 Principles of Tooth Preparation 



I 




Beveled margins will 
extend farther intra- 
sidcularly to obtain 
satisfactory esthetics. 



Fig. 7-23. A, A shoulder provides more bulk of metal than a heavy chamfer, which may facilitate the 
laboratory steps. B, A disadvantage of the shoulder bevel is that its margin must be placed deeper in the 
gingival sulcus so that the wider band of metal will be hidden (compare d with D). c, Scanning electron 
micrograph of a shoulder margin prepared with a high-speed diamond. D, This margin has been refined 
with a sharp chisel. E, This has been beveled with a tungsten carbide bur. F, This bevel was placed with 
a sharp hand instrument. 

(Microscopy by Dr. J. Sandrik, teeth prepared by Dr. G. Byrne.) 



I 



Section 2 Clinical Procedures-Part I 




Fig. 7-24. A, Nonreplacement of missing teeth has led to supraocclusion and a protrusive interfer- 
ence (arrow). B, Teeth reduced with the help of trial tooth preparations and diagnostic waxing. 
C, Restorations with anterior guidance. 



A 120-degree sloped shoulder margin (Fig. 7-17, F) 
is used as an alternative to the 90-degree shoulder 
for the facial margin of a metal- ceramic crown. The 
sloped shoulder reduces the possibility of leaving 
unsupported enamel and yet leaves sufficient bulk 
to allow thinning of the metal framework to a 
knife-edge for acceptable esthetics. 

A beveled shoulder margin (Fig. 7-17, G) is often 
recommended for the facial surface of a metal- 
ceramic restoration where a metal collar (as op- 
posed to a porcelain labial margin) is used. The 
beveling removes unsupported enamel and may al- 
low some finishing of the metal. However, a shoul- 
der or sloped shoulder is preferred for biologic and 
esthetic reasons. This allows improved esthetics be- 
cause the metal margin can be thinned to a knife 
edge and hidden in the sulcus without the need for 
positioning the margin closer to the epithelial at- 
tachment (Fig. 7-23, B). 

Occlusal Considerations. A satisfactory tooth 
preparation should allow sufficient space for devel- 
oping a functional occlusal scheme in the finished 
restoration. Sometimes a patient's occlusion is dis- 
rupted by supraerupted or tilted teeth (Fig. 7-24). 
When these teeth are prepared for restoration, the 



eventual occlusal plane must be carefully analyzed 
and the teeth reduced accordingly. Often consider- 
able reduction is needed to compensate for the 
supraeruption of abutment teeth. 

Sometimes even endodontic treatment is neces- 
sary to make enough room. However, under these 
circumstances, violating the principle of conserva- 
tion of tooth structure is preferable to the potential 
harm from a traumatic occlusal scheme. Obviously, 
careful judgment is needed, and diagnostic tooth 
preparations and waxing procedures are essential to 
determining the exact amount of reduction required 
to develop an optimum occlusion. 

Preventing Tooth Fracture. No tooth is un- 
breakable. If teeth are smashed together (as in an 
automobile accident, sport injury, or biting on a 
hard object unexpectedly), a cusp may break. Cus- 
pal fracture also can occur from par afunctional 
habits such as bruxism. 

The likelihood that a restored tooth will fracture 
can be lessened if the tooth preparation is designed 
to minimize potentially destructive stresses (Fig. 
7-25). For example, an intracoronal cast restoration 
(inlay) has a greater potential for fracture because 
when occlusal forces are applied to the restoration. 



Chapter 7 Principles of Tooth Preparation 



I 



Fracture 




L B 




L B 




Onlay 



Complete 
crown 



Cuspal protection becomes 
nmre important as the 
structural durability of the 
cusps is compromised. 



Fig. 7-25. A, An intracoronal cast restoration (inlay) can act as a wedge during cementation or func- 
tion. If the cusps are weakened, fracture will occur. B, A cuspal-coverage onlay provides better protec- 
tion but often lacks retention. C, A complete crown provides the best protection against fracture. It also 
has the best retention, but it can be associated with periodontal disease and poor esthetics. 

(Redrawn from Rosenstiel SF: In Rayne J, editor: General dental treatment, London, 1983, Kluwer Publishing.) 



it tends to wedge opposing walls of the tooth apart. 
This wedging must be resisted by the remaining 
tooth structure; if the structure is thin (as with a 
wide preparation isthmus), the tooth may fracture 
during function. Providing a cuspal coverage 
restoration (onlay) rather than an inlay lessens the 
chance of such fracture. However, although not 
conservative of tooth structure, a complete crown is 
often a better solution, because it offers the greatest 
protection against tooth fracture, tending to "hold" 
the cusps of the tooth together. 

^MECHANICAL CONSIDERATIONS 

The design of tooth preparations for fixed prostho- 
dontics must adhere to certain mechanical principles; 
otherwise, the restoration may become dislodged or 
may distort or fracture during service. These princi- 
ples have evolved from theoretical and clinical obser- 
vations and are supported by experimental studies. 
Mechanical considerations can be divided into 
three categories: 

1. Providing retention form 

2. Providing resistance form 

3. Preventing deformation of the restoration 



RETENTION FORM 

Certain forces (e.g., when the jaws are moved apart 
after biting on very sticky food) act on a cemented 
restoration in the same direction as the path of with- 
drawal. The quality of a preparation that prevents 
the restoration from becoming dislodged by such 
forces parallel to the path of withdrawal is known 
as retention. Only dental caries and porcelain failure 
outrank lack of retention as a cause of failure of 
crowns and fixed partial dentures . 48,49 

The following factors must be considered when 
deciding whether retention is adequate for a given 
fixed restoration: 

1. Magnitude of the dislodging forces 

2. Geometry of the tooth preparation 

3. Roughness of the fitting surface of the 
restoration 

4. Materials being cemented 

5. Film thickness of the luting agent 

Magnitude of the Dislodging Forces. Forces 
that tend to remove a cemented restoration along its 
path of withdrawal are small compared to those 
that tend to seat or tilt it. A fixed partial denture or 
splint can be subjected to such forces by pulling 




Section 2 Clinical Procedures-Part I 



with floss under the connectors; however, the 
greatest removal forces generally arise when excep- 
tionally sticky food (e.g., caramel) is eaten. The 
magnitude of the dislodging forces depends on the 
stickiness of the food and the surface area and tex- 
ture of the restoration being pulled. 

Geometry of the Tooth Preparation. Most fixed 
prostheses depend on the geometric form of the 
preparation rather than on adhesion for retention be- 
cause most of the traditional cements (e.g., zinc 
phosphate) are nonadhesive (i.e., they act by in- 
creasing the frictional resistance between tooth and 
restoration). The grains of cement prevent two sur- 
faces from sliding, although they do not prevent one 
surface from being lifted from another. This is anal- 
ogous to the effect of particles of sand or dust within 
machinery. They do not have a specific adhesion 
to metal, but they increase the friction between 
sliding metal parts. If sand or dust gets into an old- 
fashioned, mechanical camera or watch, the increase 
in friction can effectively jam the mechanism. 

Cement is effective only if the restoration has a 
single path of withdrawal (i.e., the tooth is shaped 
to restrain the free movement of the restoration). 
The relationship between a nut and a bolt is an ex- 
ample of restrained movement (Fig. 7-26). The nut is 
not free to move in any direction but can move only 
along the precisely determined helical path of the 
threads on the bolt. 

The relationship between two bodies, one (in this 
case a tooth preparation) restraining movement of 



Minimizing taper effectively 
limits the number of direc- 
tions in which a cast crown 
can be dislodged. 





Fig. 7-26. A, The relationship of a nut and a bolt is an ex- 
ample of restrained movement; the nut must move along a 
precisely defined helical path (arrows). B, For effective re- 
tention, a tooth preparation must constrain the movement 
of a restoration. For this to occur, it must be cylindrical. 
(See Figure 7-27.) 



the other (a cemented restoration), has been studied 
mathematically and is known in analytical mechan- 
ics as a closed lower pair of kinematic elements. In 
fixed prosthodontics, a sliding pair is the only pair 
that has relevance. It is formed by two cylindrical* 
surfaces constrained to slide along one another. The 
elements are constrained if the curve that defines 
the cylinder is closed or shaped to prevent move- 
ment at right angles to the axis of the cylinder 
(Fig. 7-27). 

A tooth preparation will be cylindrical if the axial 
surfaces are prepared by a cylindrical bur held at a 
constant angle. The gingival margin of the prepara- 
tion becomes the fixed curve of the mathematical 
definition, and the occlusoaxial line angle of the 
tooth preparation should be a replica of the gingival 
margin geometry. The curve of a complete crown 
preparation is closed, whereas the grooves of a par- 
tial crown preparation prevent movement at right 
angles to the long axis of the cylinder. However, if 
one wall of the complete crown preparation is over- 



*Cy Under is defined in its mathematical sense as the 
solid generated by a straight line parallel to another 
straight line and moving so that its ends describe a 
fixed curve. 







B 



Horizontal 

Fig. 7-27. A preparation is cyHndrical if the two hori- 
zontal cross sections of the prepared axial tooth surface 
(1 and 2) are coincident. A, This complete crown is cylindri- 
cal and therefore retentive. B, A partial crown will be reten- 
tive if its sections are coincident and perpendicular move- 
ment is prevented by grooves. C, This preparation is 
cylindrical (1 and 2 coincide) but not retentive, because it 
can move perpendicularly to the axis of the cylinder. 

(Redrawn from Rosenstiel E: Br Dent J 103:388, 1957.) 



Chapter 7 Principles of Tooth Preparation 



I 



tapered, it will no longer be cylindrical, and the ce- 
mented restoration will not be constrained by the 
preparation because the restoration then has multi- 
ple paths of withdrawal. Under these circum- 
stances, the cement particles will tend to lift away 
from rather than slide along the preparation, and 
the only retention will be a result of the cement's 
limited adhesion (Fig. 7-28). 

Taper. Theoretically, maximum retention is ob- 
tained if a tooth preparation has parallel walls. 
However, it is impossible to prepare a tooth this 
way using current techniques and instrumentation; 
slight undercuts are created that prevent the 
restoration from seating. 

An undercut is defined as a divergence between 
opposing axial walls, or wall segments, in a cervi- 
cal-occlusal direction (Fig. 7-29, A). For instance, if 
the cervical diameter of a tooth preparation at the 
margin is narrower than at the occlusoaxial junction 
(reverse taper), it will be impossible to seat a com- 
plete cast crown of similar geometry (Fig. 7-29, B). 
Undercuts can be present whenever two axial walls 
face in opposite directions (Fig. 7-29, C. Thus the 
mesial wall of a complete cast crown preparation 
can be undercut relative to the distal wall; in addi- 





Fig. 7-28. A, Cross sections 1 and 2 do not coincide, and 
the preparation thus has little retention. B, Under these cir- 
cumstances, very little friction develops between the ce- 
ment and the axial walls, and the cement is subjected to 
tensile stress. C, A retentive near-parallel preparation with 
frictional resistance. The cement is placed under shear 
stress. 
(A redrawn from Rosmstiel E: Br Dent J 103:388, 1957.) 



tion, the buccal wall can be undercut relative to the 
lingual wall; finally, in a partial veneer preparation, 
the lingual wall of a proximal groove can be under- 
cut relative to the lingual wall of the preparation. 

A slight convergence, or taper, is necessary in the 
completed preparation. As long as this taper is small, 
the movement of the cemented restoration will be ef- 
fectively restrained by the preparation and will have 
what is known as a limited path of withdrawal. As the 
taper increases, however, so does the free movement 
of the restoration, and retention will be reduced. 

The relationship between the degree of axial wall 
taper and the magnitude of retention was first 
demonstrated experimentally by Jorgensen in 
1955. He cemented brass caps on Galalith cones of 
different tapers and measured retention with a ten- 
sile-testing machine. The relationship was found to 
be hyperbolic, with retention rapidly becoming less 
as taper increased (Fig. 7-30), although the relation- 





For a crown to seat and have 
the optimal retention, all axial 
walls should have a 6-degree 
taper from cervical to occlusal. 




Fig. 7-29. A, An undercut is formed if opposing walls 
diverge. B, A crown is prepared, because an undercut 
preparation cannot "seat," since it cannot pass over the di- 
vergent walls. C, Undercuts are possible in other locations 
when fixed partial dentures or restorations with prepara- 
tion features such as grooves or boxes are prepared. Here 
one buccal facing wall (B) can be undercut relative to (four) 
lingual facing walls (L). 



I 



Section 2 Clinical Procedures-Part I 



ship was no longer hyperbolic when the internal 
surfaces of the caps were roughened. The retention 
of a cap with 10 degrees of taper* was approxi- 
mately half that of a cap with 5 degrees. Similar re- 
sults have been reported by other workers. 

Selection of the appropriate degree of taper for 
tooth preparation involves compromise. Too small a 
taper may lead to unwanted undercuts; too large 
will no longer be retentive. The recommended con- 
vergence between opposing walls is 6 degrees, 
which has been shown to optimize retention for 
zinc phosphate cement. " Recognizing this angle is 
important (Fig. 7-31), although there is no need to 
deliberately tilt a rotary cutting instrument to create 
a taper, since this will invariably lead to overprepa- 
ration. Rather, teeth are readily prepared with a ro- 
tary instrument of the desired taper held at a con- 
stant angulation. The rotary instrument should be 
moved through a cylindrical path as the tooth is 
prepared, and the taper of the instrument should 
produce the desired axial wall taper on the com- 
pleted preparation. In practice, many dentists expe- 



*In this discussion, as is generally the case in the den- 
tal literature, taper and convergence are used inter- 
changeably and refer to the angle between diametri- 
cally opposed axial walls. 



2 
1.8 
1.6 
1.4 



^ 1.2 

I 



c 
o 



c 

I 0-6 



0.6 
0.4 

0.2 



Even a slight increase in 
axial wall taper significantly 
reduces retention. 



J_ 



-L 



-L. 



-L. 



_L 



10 20 30 40 50 60 70 80 90 

Taper (degree*^) 

Fig. 7-30. Relationship between retention and conver- 
gence angle. *, Experimental values; x, calculated values 
outside the experimental range. 

(Redrawn from Jorgensen KD: Acta Odontol Scand 13:35, 

1955.) 



rience difficulty consistently avoiding excessively 
tapered preparations, particularly when preparing 
posterior teeth with limited access . 56 Some authori- 
ties recommend the routine use of grooves to reduce 
the incidence of restoration displacement. It is un- 
clear, however, whether accurate groove alignment 
is more easily achieved than axial wall convergence, 
and skillfully prepared axial walls at a minimal con- 
vergence are very conservative of tooth structure. 

Surface Area. Provided the restoration has a 
Hmited path of withdrawal, its retention depends 
on the length of this path or, more precisely, on the 
surface area in sliding contact. Therefore, crowns 
with long axial walls are more retentive than those 
with short axial walls,-" and molar crowns are more 
retentive than premolar crowns of similar taper. 
Surfaces where the crown is essentially being pulled 
away from rather than sliding along the tooth, such 
as the occlusal surface, do not add much to total 
retention. 

Stress Concentration. When a retentive fail- 
ure occurs, cement often adheres to both the tooth 
preparation and the fitting surface of the restora- 
tion. In these cases, cohesive failure occurs through 
the cement layer because the strength of the cement 
is less than the induced stresses. A computerized 
analysis of these stresses-' ', reveals that they are not 
uniform throughout the cement but are concen- 
trated around the junction of the axial and occlusal 
surfaces. Changes in the geometry of the prepara- 
tion (e.g., rounding the internal line angles) may re- 
duce stress concentrations and thus increase the re- 
tention of the restoration. 

Type of Preparation. Different types of prepa- 
ration have different retentive values that corre- 
spond fairly closely to the surface area of the axial 




Fig. 7-31 . The recommended convergence angle is 
6 degrees. This is a very slight taper. (The angle between 
the hands of a clock showing 12:01 is 5 1/2, degrees.) 



Chapter 2 Principles of Tooth Preparation 



I 



walls, as long as other factors (e.g., taper) are kept 
constant. Thus the retention of a complete crown is 
about double that of partial-coverage restorations 59 
(Fig. 7-32). 

Adding grooves or boxes (Fig. 7-33) to a prepara- 
tion with a limited path of withdrawal does not 
markedly affect its retention because the surface 
area is not increased significantly. However, where 
the addition of a groove limits the paths of with- 
drawal, retention is increased ''"''' 

Roughness of the Surfaces Being Cemented. 

When the internal surface of a restoration is very 
smooth, retentive failure occurs not through the ce- 
ment but at the cement-restoration interface. Under 
these circumstances, retention will be increased if the 



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Preparations 

F 1 9 . 7 - 3 2 * Retention of different p rep a ra tion d esigns, 
(from Potts RG et at J Prosthet Dent 43:303, 1980.) 





•i y 



Internal features 
effectively increase 
resistance. 



Fig. 7-33. Retention form of an excessively tapered 
preparation can be increased by adding grooves or pin- 
holes, because these v^^ill limit the paths of withdraw^al. 



restoration is roughened or grooved . The casting 
is most effectively prepared by air- abrading the fit- 
ting surface with 50 um of alumina. This should be 
done carefully to avoid abrading the polished sur- 
faces or margins. Airborne particle abrasion has been 
shown65 to increase in vitro retention by 64%. 

Failure rarely occurs at the cement-tooth inter- 
face. Therefore, deliberately roughening the tooth 
preparation hardly influences retention and is not 
recommended, because roughness adds to the diffi- 
culty of impression making and waxing. 

Materials Being Cemented. Retention is af- 
fected by both the casting alloy and the core or 
buildup material. Laboratory testing results have 
yet to be confirmed by longer-term clinical studies, 
but it appears that the more reactive the alloy is, the 
more adhesion there will be with certain luting 
agents. Therefore, base metal alloys are better re- 
tained than less reactive high-gold content metals 
The effect of adhesion to different core materials 
also has been tested, with conflicting results. One 
laboratory study67 examining adhesion between ce- 
ments and core materials found that the cement ad- 
hered better to amalgam than to composite resin or 
cast gold. However, when crowns were tested for 
retention, higher values were found with the com- 
posite resin than with amalgam cores . The differ- 
ences may have been due to dimensional changes of 
the core materials, although the clinical implications 
of this finding are not clear. 

Type of Luting Agent. The type of luting agent 
chosen affects the retention of a cemented restora- 
tion .69 However, the decision regarding which 
agent to use is also based on other factors. In gen- 
eral, the data suggest that adhesive resin cements 
are the most retentive (Fig 7-34), although 

long-term clinical evidence about the durability of 
the bond is not available. 

Film Thickness of the Luting Agent. There is 
conflicting evidence about the effect of increased 
thickness of the cement film on retention of a 
restoration. This may be important if a sHghtly over- 
sized casting is made (as when the die- spacer tech- 
nique is used). 

The factors that influence the retention of a ce- 
mented restoration are summarized in Table 7-3. 

RESISTANCE FORM 

Certain features must be present in the preparation 
to prevent dislodgment of a cemented restoration. 
Mastication and parafunctional activity may subject 
a prosthesis to substantial horizontal or oblique 



■ 



Section 2 Clinical Procedures-Part I 



300 1 



O Ayad et al ■ Tjan snd Lt 

M Cototioviky and Zkbn ■ Mojon d al 
S Wi^kon et al ■ M.»;<>ni?r et r\ 






Q- 200- 



c 
N 
'o 

c 

o 



.2 100 







Class 
fonomer 



Resin 



Adhesive Polycarboxylale 
Resin 



Fig. 7-34. Crown retention studies. Effect of luting agent. These six in vitro studies evaluated the ef- 
fect of luting agent on crown retention.9 0-92 The data were normalized as a percentage of the reten- 
tion value with zinc phosphate cement. Adhesive resins had consistently greater retention than zinc 
phosphate. Conventional resins and glass ionomers yielded less consistent results. 
(From Rosenstiel SF et al: 1 Prosthet Dent 80:280, 1998.) 



forces. These forces are normally much greater than 
the ones overcome by retention, especially if the 
restoration is loaded during eccentric contact be- 
tween posterior teeth. Lateral forces tend to displace 
the restoration by causing rotation around the gin- 
gival margin. Rotation is prevented by any areas of 
the tooth preparation that are placed in compres- 
sion, called resistance areas (Fig. 7-35). Multiple rcsis- 
tance areas cumulatively make up the resistance 
form of a tooth preparation. 

Adequate resistance depends on the following: 

1. Magnitude and direction of the dislodging 
forces 

2. Geometry of the tooth preparation 

3. Physical properties of the luting agent 

Magnitude and Direction of the Dislodging 

Forces. Some patients can develop enormous bit- 
ing forces. Gibbs et al" discovered one individual 
(Fig. 7-36) who had a biting force of 4340 N (443 
kg).* Although this is considered extraordinary, 
restorations should nevertheless be designed to 
withstand forces approaching such magnitude. In 
one laboratory study,-" a complete crown cemented 
on a nickel-chromium test die was found to be ca- 
pable of withstanding over 13,500 N (1400 kg)-a 
far greater force than would occur in the mouth- 
before becoming displaced (Fig. 7-37). 



*This compares with the world record super heavy- 
weight (105+ kg) snatch of 205.5 kg. 



When quantifying resistance, 
ask youjself the foUowing 
question: How much tooth 
structure needs to break, or 
how much does the crown 
have to deform in order to 
dislodge this restoration? 




Lingual 



Buccal 



Mesial 



Distal 



Fig. 7-35. The resistance area (RA) of a complete crown 
is placed under compression when a lateral force (F) is ap- 
plied. NRA, Nonresisting area. 

(Redrawn from Hegdahl T, Silness ]\\ Oral Rehabil 4:201, 1977.) 



In a normal occlusion, biting force is distributed 
over all the teeth; most of it is axially directed. If a 
fixed prosthesis is carefully made with a properly de- 
signed occlusion, the load should be well distributed 
and favorably directed (see Chapter 4). However, if a 
patient has a biting habit such as pipe smoking or 



Taper 

Surface area 
Type of preparation 
Surface texture 
Film tfiickness 
Luting agent 



Greater Retention 



Paralld 



Large 



Molar complete crown 



Rough 



Adhesive resin 



-^ 6 degrees 



Premolar complete crown 



Partial crown 



Effect uncertain 



Glass ionomer 



Polycarboxylate 
Zinc phosphate 



Lesser Retention 



T A&LE 7-3 
Excessive 



Small 



-♦- Intracoronal restoration 



Smoofh 



"*^ Zinc oxid&-eugenol 



O 

-a 

r-r 

ru 

Ml 

3' 

n 
FT 



3* 



§ 




I 



Section 2 Clinical Procedures-Part I 



bruxing, it may be difficult to prevent fairly large 
oblique forces from being applied to a restoration. 
Consequently the completed tooth preparation and 
restoration must be able to withstand considerable 
oblique forces as well as the normal axial ones. 

Geometry of the Tooth Preparation. As with re- 
tention, preparation geometry plays a key role in at- 
taining desirable resistance form. The tooth prepara- 
tion must be shaped so that particular areas of 
the axial wall will prevent rotation of the crown. 




Fig. 7-36. Mr. H. sitting beside 443 kg of gymnasium 
weights to illustrate the magnitude of his biting strength. 

(Reproduced from Gibbs CH et al: ] Prosthet Dent 56:226,1986.) 



Hegdahl and Silness79 analyzed how these resisting 
areas alter as changes are made in the geometry of the 
tooth preparation. They demonstrated that increased 
preparation taper and rounding of axial angles tend 
to reduce resistance. Short tooth preparations with 
large diameters were found to have very little resis- 
tance form. In general, molar teeth require more par- 
allel preparation than premolar or anterior teeth to 
achieve adequate resistance form."" The relationship 
between preparation height, or diameter, and resis- 
tance to displacement is approximately linear. , ' 

A partial-coverage restoration may have less re- 
sistance (Fig. 7-38) than a complete crown because it 



Fig. 7-37. Resistance of different preparation designs. 
The line connects preparations with statistically similar dis- 
placement forces (p > 0.05). 
(Modified from Kishimoto M et al: J Prosthet Dent 49: 188, 1983.) 



BUCCAL F ^-^ 




LINGUAL 



B 



C BUCCAL 



RA.^ 




LINGUAL 



Fig. 7-38. Resistance form of partial and complete crowns. A, The buccoaxial wall (RA) of a complete 
crown should provide good resistance to rotation around a lingual axis. B, In a partial crown, resistance 
must be furnished by mesial and distal grooves. C, In a short or excessively tapered complete crown, re- 
sistance form is minimal because most of the buccal wall is missing. A mesiodistal groove should be 
placed to increase resistance form. D, Poor resistance form is less a problem in a short partial crown, 
provided the grooves have sufficient definition. However, lack of retention form may indicate the need 
for complete coverage. 



Chapter 7 Principles of Tooth Preparation 



I 



has no buccal resistance areas. Resistance must be 
provided by boxes or grooves (Fig. 7-39) and will be 
greatest if they have walls that are perpendicular to 
the direction of the applied force. Thus U-shaped 
grooves or flared boxes provide more resistance than 
V-shaped ones, -y The resistance form of an excessively 
tapered preparation can be improved by adding 
grooves or pinholes, because these interfere with 
rotational movement and in so doing subject 
additional areas of the luting agent to compression. 

Physical Properties of the Luting Agent. Re- 
sistance to deformation is affected by physical prop- 
erties of the luting agent, such as compressive 
strength and modulus of elasticity. To satisfy 
ADA/ANSI specification no. 96 (ISO 9917), the 
compressive strength of zinc phosphate cement 
must exceed 70 MPa* at 24 hours (Fig. 7-40). Glass 

*One megapascal (MPa) equals 1 miUion newtons per 
square meter. 





Fig. 7-39. A, The grooves of a partial crown should pro- 
vide the maximum resistance to rotation around an axis sit- 
uated at the Unguogingival margin. B, The lingual walls of 
the groove-the resistance areas (RA)-should be prepared 
perpendicular to the direction of force (F). 



ionomer cements and most resins have higher com- 
pressive strength, whereas polycarboxylates have 
similar values. ^^ 

Increasing temperature has a dramatic effect on 
the compressive strength of luting agents, particu- 
larly weakening reinforced zinc oxide-eugenol ce- 
ment (Fig. 7-41). An increase from room tempera- 
ture (23° C) to body temperature (37° C) halves the 
compressive strength of reinforced zinc oxide- 
eugenol cements, and a rise in temperature to 50c C 
(equivalent to hot food) reduces the compressive 
strength by over 80% .83 Equivalent testing of more 
modern cements has not been reported. 

Zinc phosphate cements have a higher modulus 
of elasticity than do poly carboxy late cements, 
which exhibit relatively large plastic deformation. 
This may account for the observation that the reten- 
tive ability of polycarboxylate cement is more de- 
pendent on the taper of the preparation than is the 
retention with zinc phosphate cement."-' 

The factors that affect the resistance to displace- 
ment of a cemented restoration are summarized in 
Table 7-4. 

DEFORMATION 

A restoration must have sufficient strength to pre- 
vent permanent deformation during function (Fig. 
7-42). Otherwise, it will fail (typically at the restora- 
tion-cement, or the metal-porcelain, interface). This 
may be a result of inappropriate alloy selection, in- 
adequate tooth preparation, or poor metal-ceramic 
framework design. 

Alloy Selection. Although Type I and Type II 
gold alloys (see Chapter 22) are satisfactory for in- 
tracoronal cast restorations, they are too soft for 



300 1 



Study: 



I White and Vu 
I Kerby el a I 



D CiitUini-Lorente et a I 

D Miyamotq ei al 




ADA/ANSI 

specification ni>. 96 



Zinc Po I ycarbcxy I ate Glass 

phosphate ionomer 



ionomer 



Resin 



Adhesive 

resin 



Fig. 7-40. Compressive strength of luting agents. Higher- strength values were reported in these stud- 
ies with the resin cements and glass ionomers than with zinc phosphate or polycarboxylate. Resin- 
modified glass ionomer exhibited greater variation than other cements. 

(From Ros.nsti.i sF et ai : J Prosthct Dcnt 80:280, 1998) 



I 



Section 2 Clinical Procedures-Part I 



n«=c 




ADA speciftcjtion 
no, a (37° O 



ZOE + EBA- Al,(), 



/( )\- 



Zinc [ihusphate. Pulycarboxylate 



Fig. 7-41 . Compressive strength of luting agents at different temperatures. 
(Redrawn from MesuFP: \ Prosthet Dent 49:59, 1983.) 



Dislcxiging forces 

Tap«r 

Oiometer 

Height 

Type of preparation 

Luting ogent 



fliv^hor ResisLiAce 



Habih 

Minimum 

Small (premolar) 
Long 



Eccentric interferences 
— ^ 6 degrees 



Complete coverage 

AcJliesive resin -^ Glass ionomer 



-^ Average 



-^ Partial coverage 



TABLE 7-4 



Lowt'r Rosistnnco 



Anterior guidance 
-^ Excessive 
Large (molar) 

N- Short 

Ofiloy 



Zinc phosphate -^ Poiycarboxylate -^ Zinc oxide-eogenol 




Fig. 7-42. Ceramic failure resulting from deformation of 
the metal substructure. 

crowns and fixed partial dentures, for which Type 
HI or Type IV gold alloys (or an appropriate 
low-gold alternative) are chosen. These are harder, 
and their strength and hardness can be increased by 
heat treatment. 

High-noble metal content metal-ceramic alloys 
have a hardness equivalent to that of Type IV golds, 
whereas nickel-chromium alloys are considerably 
harder. These may be indicated when large forces 
are anticipated, such as with a long- span FPD, al- 
though their use presents certain problems (see 
Chapter 16). 



Adequate Tooth Reduction. Even the stronger 
alloys need sufficient bulk if they are to withstand 
occlusal forces. Largely based on empirical data, 
there should be a minimum alloy thickness of about 
1.5 mm over centric cusps (buccal in the mandible, 
Ungual in the maxillae). The less stressed noncentric 
cusps can be protected with less metal (1 mm is ad- 
equate in most circumstances) for a strong and 
long-lasting restoration. Occlusal reduction should 
be as uniform as possible, following the cuspal 
planes of the teeth; this will ensure that sufficient 
occlusal clearance is combined with preservation of 
as much tooth structure as possible. In addition, an 
anatomically prepared occlusal surface (Fig. 7-43) 
will give rigidity to the crown because of the "cor- 
rugated effect" "6 of the planes. 

When teeth are malaligned or overerupted, the 
occlusal surface needs to be prepared with the 
eventual restoration in mind. For example, a 
supraerupted tooth may need considerably more 
than 1.5 mm of reduction to result in adequate clear- 
ance to reestablish an ideal occlusal plane (Fig. 
7-44). Diagnostic tooth preparation and waxing are 
helpful in determining the correct tooth reduction. 

Margin Design. Distortion of the restoration 
margin is prevented by designing the preparation 



Chapter 7 Principles of Tooth Preparation 



I 





Fig. 7-43. Anatomic occlusal reduction is conservative of tooth structure and gives rigidity to the 
restoration. 




Fig. 7-44. This molar relationship is a result of extreme occlusal wear. 
When designing a tooth preparation, consideration of the eventual oc- 
clusal plane is essential. This is done with the aid of a diagnostic waxing 
procedure. 



^^ii^^D^^B*^ 




^(tMUm^ 


■',iA ■ 1A 


i \ f "^ / '] 


M'^ ^ ^ *Sl ■• 


L-V ^- i 


^»i&/^ /^j«^"- * 


rr> ■ 


m^^^^H 


y-^^^m^^^^ .^-^ 


^^^^"^^^B^^B 


Wi,^!j^^^K^^^^^S^fbkm^^m^ 




rf^.^ ■ ♦ ^ 








# J 





Fig. 7-45. Grooves and ledges provide rigidity in pinledges (A to C) and partial-coverage 
restorations (D). 



outline to avoid occlusal contact in this area. Also, 
tooth reduction should provide sufficient room for 
bulk of metal at the margin to prevent distortion. As 
discussed earlier, one disadvantage of the feath- 
eredge preparation is that the resulting thin layer of 
gold is not as strong as the comparatively thicker 
restoration of a chamfer preparation. 

The grooves and ledges incorporated in a partial- 
coverage restoration provide essential strengthen- 
ing for the casting, particularly an anterior pinledge 
retainer (Fig. 7-45). 



ESTHETIC CONSIDERATIONS 

The restorative dentist should develop skill in de- 
termining the esthetic expectations of the patient. 
Patients prefer their dental restorations to look as 
natural as possible. However, care must be taken 
that esthetic considerations are not pursued at the 
expense of a patient's long-term oral health or func- 
tional efficiency. 

At the initial examination it is important to make 
a full assessment of the appearance of each patient, 
noting which areas of which teeth show during 



I 



Section ?, Clinical Procedn res-Part I 



smiling, talking, and laughing. The patient's es- 
thetic requirements must be discussed and related 
to oral hygiene needs and the potential for disease. 
The final decision regarding an appropriate restora- 
tion can then be made with the full cooperation and 
informed consent of the patient. 

METAL- CERAMIC RESTORATIONS 

The poor appearance of some metal-ceramic 
restorations is often due to insufficient porcelain 
thickness. On the other hand, adequate porcelain 
thickness is sometimes obtained at the expense of 
proper axial contour (such overcontoured restora- 
tions almost invariably lead to periodontal disease). 
In addition, the labial margin of a metal-ceramic 
crown is not always accurately placed. To correct all 
these deficiencies, certain principles are recom- 
mended during tooth preparation that will ensure 
sufficient room for porcelain and accurate place- 
ment of the margins. Otherwise, good appearance 
would be achievable only at the expense of peri- 
odontal health. 

Facial Tooth Reduction. If there is to be suffi- 
cient bulk of porcelain for appearance and metal for 
strength, adequate reduction of the facial surface is 
essential. The exact amount of reduction will de- 
pend to some extent on the physical properties of 
the alloy used for the substructure as well as on the 
manufacturer and the shade of the porcelain. A min- 
imum reduction of 1.5 mm typically is required for 
optimal appearance. Adequate thickness of porce- 
lain (Fig. 7-46) is needed to create a sense of color 
depth and translucency. Shade problems are fre- 
quently encountered in maxillary incisor crowns at 
the incisal and cervical thirds of the restoration. 



Metal framework 



Opaque layer 




Critical reflectance 



Porcelain 



Fig. 7-46. Adequate porcelain thickness is essential for 
preventing direct liglit reflection from the highly pigmented 
opaque porcelain. The most critical areas are the gingival 
and incisal thirds; in practice, opaque modifying stains are 
often used in these areas. 

(Redrawn from McLean jw : The scieuce and art of dental ce- 
ramics, vol 1, Chicago, 1979, Quintessence Publishing.) 



where direct light reflection from the opaque layer 
can make the restoration appear very noticeable. Be- 
cause opaque porcelains generally have a different 
shade from body porcelains, they often need to be 
modified with special stains in these areas." 

With very thin teeth (e.g., mandibular incisors) it 
may be impossible to achieve adequate tooth reduc- 
tion without exposing the pulp or leaving a severely 
weakened tooth preparation. Under these circum- 
stances a less than ideal appearance may have to be 
accepted. 

The labial surfaces of anterior teeth should be 
prepared for metal-ceramic restorations in two 
distinct planes (Fig. 7-47). If they are prepared in a 
single plane, insufficient reduction in either the 
cervical or the incisal area of the preparation will 
result. 

Incisal Reduction. The incisal edge of a 

metal-ceramic restoration has no metal backing and 
can be made with a translucency similar to that of 
natural tooth structure. An incisal reduction of 2 
mm is recommended for good esthetics. Excessive 
incisal reduction must be avoided because it re- 
duces the resistance and retention form of the 
preparation. 

Proximal Reduction. The extent of proximal re- 
duction is contingent on exact predetermination of 
the location of the metal-ceramic junction in the 
completed restoration. The proximal surfaces of an- 
terior teeth will look most natural if they are re- 
stored as the incisal edges, without metal backing. 
This will allow some light to pass through the 
restoration in a manner similar to what occurs on a 
natural tooth (Fig. 7-48). Obviously, if the restora- 
tion is part of a fixed partial denture, the need for 
connectors will make this impossible. 

Labial Margin Placement. Supragingival mar- 
gin placement has many biologic advantages. The 
restorations are easier to prepare properly and eas- 




Fig. 7-47. Recommended tooth preparation for a 
metal-ceramic restoration. The facial reduction has two dis- 
tinct planes. 



Chapter i Principles of Tooth Preparation 



I 



ier to keep clean. Nevertheless, subgingival margins 
may be indicated for esthetic reasons, particularly 
when the patient has a high lip line and the use of a 
metal collar labial margin is contemplated. 

The patient's smile is observed as part of the ini- 
tial examination (see Chapter 1). It is important to 
record which teeth and which parts of each tooth 
are exposed. Patients with a high lip line, which ex- 
poses considerable gingival tissue, present the 
greatest problem if complete crowns are needed. 
Where the root surface is not discolored, appear- 
ance can be restored with a metal-ceramic restora- 
tion having a supragingival porcelain labial margin- 
sometimes called a "collarless" design (see Chapter 
24). If the patient has a low lip line, a metal 
supragingival collar may be placed because the 
metal is not seen during normal function. Metal 
margins generally have a more accurate fit than 
porcelain margins. 

However, it cannot be assumed that the patient 
will be happy with a supragingival metal collar just 
because the metal is not visible during normal func- 
tion. Some patients have reservations about ex- 
posed metal, and the advantages of such supragin- 
gival margins must be carefully explained before 
treatment. 

Metal collars can be hidden below the gingival 
crest, although there will be some discoloration if 
the gingival tissue is thin. Successful margin place- 
ment within the gingival sulcus requires care to en- 
sure that inflammation and/or recession, with re- 
sulting metal exposure, are avoided or minimized. 
The periodontium must be healthy before the tooth 
is prepared. If periodontal surgery is needed, the 
sulcular space should not be eliminated completely; 
rather, a postsurgical depth of about 2 mm should 
be the objective. Sufficient time should be allowed 
after surgery for the periodontal tissues to stabilize. 
Wise found that the gingival crest does not stabi- 
lize until 20 weeks after surgery. 




Margins should not be placed so far apically that 
they encroach on the attachment; extension to 
within 1.5 mm of the alveolar crest will lead to bone 
resorption. The margin should follow the contour 
of the free gingiva, being further apical in the mid- 
dle of the tooth and further incisal interproximally. 
A common error (Fig. 7-49) is to prepare the tooth so 
the margin lies almost in one plane, with exposure 
of the collar labially and irreversible loss of bone 
and papilla proximally. 

PARTIAL-COVERAGE RESTORATIONS 

Whenever possible, accomplishment of an estheti- 
cally acceptable result without the use of metal- 
ceramic crowns is preferred, not only because tooth 
structure is conserved but also because no restora- 
tive material can approach the appearance of intact 
tooth enamel. Esthetic partial-coverage restorations 
depend on accurate placement of the potentially 
visible facial and proximal margins. Understand- 
ably, many patients will not readily accept a visible 
display of metal. If a partial-coverage restoration is 
poorly prepared, the patient may demand that it be 
replaced by a metal-ceramic crown, and the result 
will be unnecessary loss of tooth structure and a 
greater potential for tissue damage. 

Proximal Margin. Placement of the proximal 
margins (particularly the mesial, generally more 
visible, margin) is critical to the esthetic result of a 
partial-coverage restoration. The rule here is to 




Fig. 7-48. The proximal surfaces of these anterior 
metal-ceramic crowns are restored in porcelain, which al- 
lows light to be transmitted for maximum esthetics. 



Fig. 7-49. A, Poor preparation design. The apical mar- 
gin of the preparation does not follow the free gingival 
contours. B, The restoration displays a metal collar labially, 
and the deep proximal margins have led to periodontal 
disease. 



I 



Section 2 Clinical Procedures-Part I 



place the margin just buccal to the proximal contact 
area, where metal will be hidden by the distal line 
angle of the neighboring tooth. Tooth preparation 
angulation is critical and should normally follow 
the long axes of posterior teeth and the incisal two 
thirds of the facial surface of anteriors. If a buccal or 
lingual tilt is given to the tooth preparation, metal 
may be visible (Fig. 7-50). 

The distal margin of posterior partial-coverage 
restorations is less visible than the mesial margin. 
Often in this area it is advantageous to extend the 
preparation farther beyond the contact point for 
easier preparation and finishing of the restoration 
and better access for oral hygiene. 

Facial Margin. The facial margin of a maxillary 
partial-coverage restoration should be extended just 



beyond the occlusofacial line angle. A short bevel is 
needed to prevent enamel chipping. A chamfer can 
be placed where appearance is less important (e.g., 
on molars) because this will provide greater bulk of 
metal for strength. 

If the buccal margin of metal is correctly shaped 
(Fig. 7-51), it will not reflect light to an observer. As 
a result, the tooth will appear to be merely a little 
shorter than normal and not as though its buccal 
cusp is outlined in metal. If the buccal margin is 
skillfully placed following the original cuspal con- 
tour, the final restoration will have an acceptable 
appearance. 

When mandibular partial cast crowns are made, 
metal display is unavoidable because the occlusal 
surface of mandibular teeth can be seen during 
speech. A chamfer, rather than a bevel, is recom- 




Clearance must be sufficient 
to permit fabrication of a die 
system but should rrunimize 
the display of metal. 




Fig. 7-50. A, Correct placement of the mesial margin of a 
partial-coverage restoration is essential to good esthetics. To 
allow proper access for finishing, the restoration must extend 
just beyond the contact area, but the metal must remain hid- 
den from the casual observer. B, The tooth should be pre- 
pared in its long axis; otherwise, metal will be displayed. 



LiHht :z 




Fig. 7-51. A, The facial margin of a partial crown should be shaped so that hght is not reflected di- 
rectly to the observer. B, A three-unit FPD. The mesial abutment is canine shaped to look like a lateral in- 
cisor. The distal abutment is a partial crown, which proved to be esthetically acceptable because the fa- 
cial surface had been correctly contoured. 



mended for the buccal margin because it provides a 
greater bulk of metal around the highly stressed 
centric cusp (Fig. 7-52). If the appearance of metal is 
unacceptable to the patient, a metal-ceramic restora- 
tion with porcelain coverage on the occlusal surface 
can be made. 

Anterior partial-coverage restorations can be fab- 
ricated to show no metal (Fig. 7-53), but their prepa- 
ration requires considerable care. The facial margin 
is extended just beyond the highest contour of the 
incisal edge but not quite to the incisolabial line an- 
gle. Here the metal will protect the tooth from chip- 
ping but will not be visible. 



Chapter 7 Principles of Tooth Preparation 

PLANNING AND EVALUATING 
TOOTH PREPARATIONS 



■ 




Fig. 7-52. A substantial chamfer is recommended for the 
centric buccal cusp of a mandibular partial cast crown. It 
will provide greater bulk of metal in a stressed area. 



mtrji^ 


^^MHI^^V^^^^^^^^^H 


l^r 


m^ 


^ * 




\ 


m 




Fig. 7-53. A, Teeth can be prepared for partial-coverage 
restorations that do not show any metal. Success depends 
on very careful margin placement. B, The incisal edge is not 
completely covered. The restoration margin is located be- 
tween the highest point of the incisal contour and the in- 
cisofacial angle. 



Tooth preparation is a technically complicated and 
irreversible procedure. Thus it is the practitioner's 
responsibility to carry it out properly every time. 
Mistakes are often difficult, if not impossible, to 
correct. 

DIAGNOSTIC TOOTH PREPARATIONS 
Diagnostic tooth preparations are performed on ar- 
ticulated casts before the actual clinical preparation. 
They yield information with regard to the following: 
e Selecting the appropriate path of withdrawal 
for a fixed partial denture, particularly when 
the abutment teeth are tilted or have an atypi- 
cal coronal contour (Fig. 7-54) 

• Determining the best location for the facial 
and proximal margins of a partial-coverage 
restoration so the metal will not be visible (Fig. 
7-55) 

• Deciding on the amount of tooth reduction 
necessary to accomplish a planned change in 
the occlusion 

Another advantage of diagnostic tooth prepara- 
tions is that the operator can practice each step of the 
intended restoration. Mistakes are not permanently 
destructive. Additionally, diagnostic preparations 
can be used in the prefabrication of provisional 
restorations, significantly reducing the appointment 
time at tooth preparation (the indirect/direct tech- 
nique is described in Chapter 15). 

Diagnostic Waxing Procedures (Fig. 7-56). For 
all but the most straightforward prosthodontic treat- 
ment plans, a diagnostic waxing procedure should be 
performed. This is done on diagnostic tooth prepara- 
tions and establishes the optimum contour and oc- 
clusion of the eventual prosthesis. The procedure is 
of particular benefit if the patient's occlusal scheme 
or anterior (incisal) guidance requires alteration. 




Fig. 7-54. Selecting the best path of withdrawal for a 
fixed partial denture with the aid of diagnostic tooth 
preparations. 



I 



Section 2 Clinical Procedures-Part I 




Fig. 7-55. Diagnostic tooth preparations are extremely 
helpful in determining the ideal reduction for esthetic par- 
tial-coverage restorations. 




Evaluative Procedures during Tooth Prepara- 
tion. Each step of a tooth preparation should be 
carefully evaluated with direct vision or indirectly 
with a dental mirror. Alignment of multiple abut- 
ment teeth can be a special problem, and using the 
mirror helps to superimpose the image of adjacent 
abutment teeth. Complex preparations should be 
evaluated by making an alginate impression and 
pouring it in fast- setting stone. A dental surveyor 
(Fig. 7-57) can then be used to precisely measure the 
axial inclinations of the tooth preparation. The less 
experienced dentist may hesitate to make such an 
impression for fear of losing time. However, the in- 
formation obtained often saves time in subsequent 
procedures by identifying problems that can then be 
addressed immediately. During tooth preparation, 
it is useful to learn to use the contraangle handpiece 
as both a measuring and a cutting instrument. This 
is done by concentrating on the top surface of the 
turbine head, which is perpendicular to the shank of 
the bur. If the top surface is kept parallel to the oc- 
clusal surface of the tooth being prepared, the bur 
will automatically be in the correct orientation (Fig. 
7-58). To prevent undercuts or excessive conver- 
gence during axial reduction, the handpiece must 
be maintained at the same angulation. The correct 
taper is imparted by the diamond instrument. Keep- 
ing the turbine head at its correct angulation ini- 
tially is often most effectively done by supporting it 
with a finger of the opposite hand. 

PATIENT AND OPERATOR POSITIONING 

Learning the proper patient and operator positions 
is as beneficial as learning the proper preparation 




Fig. 7-56. A, B, Diagnostic waxing procedure. 

(Courtesy Dr. M. Chen.) 



Fig. 7-57. A dental surveyor can be used to evaluate the 
axial alignments of a tooth preparation. 



Chapter 7 Principles of Tooth Preparation 



I 



steps. Of particular importance are the advantages 
of obtaining a direct view of the preparation, which 
is always preferred to an indirect or mirror view. 
However, certain areas (e.g., the distal surfaces of 
maxillary molars) cannot be seen directly. 

Inexperience, coupled with a hesitation to move 
the patient's head into a more favorable position, 
can unnecessarily complicate tooth preparation. For 
instance, having the patient rotate the head to the 
left or right side can considerably improve the visi- 
bility of molar teeth that are being prepared. In most 
instances a direct view can be obtained by subtly 
changing the operator's or the patient's position. 
Having the patient open maximally does not neces- 
sarily provide the best view. If the jaw is partially 
open, the cheek may be retracted more easily (Fig. 
7-59), and if the patient is encouraged to make a lat- 
eral excursion, the distobuccal line angle, together 
with the buccal third of the distal wall, may be seen 



The correct taper is 
established by moving 
the tapered diamond 
parallel to itself around 

the tooth. 




Fig. 7-58. Top surface of the handpiece held parallel to 
the occlusal surface. The bur is in correct axial alignment. 



directly. In practice, the mirror is essential only to 
visualizing a small portion of the distal surface. 
When preparing a complete crown, the parts of the 
tooth most easily seen should be prepared first, 
leaving the other areas for preparation with the help 
of the mirror as a final stage. 

(] SUMMARY 

The principles of tooth preparation can be catego- 
rized into biologic, mechanical, and esthetic consid- 
erations. Often these principles conflict, and the prac- 
titioner must decide how the restoration should be 
designed. One area may be given too much empha- 
sis, and the long-term success of the procedure may 
be limited by a lack of consideration of other factors. 
Experience will help in determining whether 
preparations are "complete." Each tooth prepara- 
tion must be measured by clearly defined criteria, 
which can be used to identify and correct problems. 
Diagnostic tooth preparations and evaluative im- 
pressions are often very helpful. The types of prepa- 
ration described in the following chapters are ex- 
plained in a step-by-step format. Understanding the 
pertinent theories underlying each step is crucial. 
Successful preparation can be obtained most easily 
by systematically following the steps. It is critical to 
refrain from "jumping ahead" before the previous 
step has been evaluated and, if necessary, corrected. 
If the clinician proceeds too rapidly, precious chair 
time will be lost, and the quality of the preparation 
will probably suffer. 



awssmLi 



axial inclination: 1 : the relationship of the long axis of a 
body to a designated plane 2: in dentistry, the align- 
ment of the long axis of a tooth to a horizontal plane. 




Fig. 7-59. Careful patient positioning can help obtain a direct view during tooth preparation. A, Of- 
ten access is better if tiie mouth is not open maximally, because partial opening allows the cheek to be 
more easily retracted. B, Access to the buccal surface. C, Access to the lingual surface. A direct view is 
obtained by tilting the patient's head. 



I 



Section 2 Clinical Procedures-Part I 



y Q^w^iiofi^ 



1 , Discuss how ^he manipulation and condition of the armomentarium being used can contribufe to injury. 

2, Discuss optimal occlusocervical margin placement. What are some reasons for deviating from the ideal? 
Why? 

3, Discuss the difference between retention and resistance. What can be done to enhance retention, and 
what con be done to improve the resistance form of o tooth preparation? 

4, Discuss six different finish line configurations. Discuss their advanfages, disadvantages, indications, and 
contraindication as applicable. 

5, Whot ts on undercut? How is an undercut eliminated? Can a buccal and lingual wall be undercut relative 
to each other? Why or why no!? 

6, Whot are the differences in retention and resistance form between a partial veneer crown preparation 
and complete cost crown preporation on the same tooth? How does clinical crown length and tooth size 
influence either? Why? 

7, List six different means of conserving roofh structure during tooth preporaHon design ond exploin why they 
result in the objective. 

8, What is the purpose of diagnostic waxing? Give four indScotions for a diagnostic waxing procedure. 



axis of preparation : the planned line or path of place- 
ment and removal for a dental restoration. 

1 bevel: n (1611): a slanting edge. 

2 bevel: vt: the process of slanting or sloping the finish 

Hnes and curves of a tooth preparation. 

chamfer: n 7; a finish line design for tooth preparation 
in which the gingival aspect meets the external ax- 
ial surface at an obtuse angle 2: a small groove or 
furrow 3: the surface found by cutting away the an- 
gle of intersection of two faces of a piece of material 
(i.e., stone, metal, wood): a beveled edge. 

clearance: n obs: a condition in which bodies may pass 
each other without hindrance. Also, the distance be- 
tween bodies (GPT-4). 

clinical crown: the portion of a tooth that extends from 
the occlusal table or incisal edge to the free gingival 
margin. 

divergence: n (1656) 1: a drawing apart as a surface 
extends away from a common point 2: the reverse 
taper of walls of a preparation for a restoration- 
divergency n, pi -cies (1709). 

draw: vt: the taper or convergence of walls of a prepa- 
ration for a restoration; slang-DRAFT, DRAUGHT. 

finish line: n (1899) 1: a line of demarcation 2: the pe- 
ripheral extension of a tooth preparation 3: the 
planned junction of different materials 4: the termi- 
nal portion of the prepared tooth. 

groove: n: a long narrow channel or depression, 
such as the indentation between tooth cusps or 
the retentive features placed on tooth surfaces to 
augment the retentive characteristics of crown 
preparations. 

interocclusal clearance: 1: the arrangement in which 
the opposing occlusal surfaces may pass one an- 
other without any contact 2: the amount of reduc- 
tion achieved during tooth preparation to provide 
for an adequate thickness of restorative material. 



margin: n (14c): the outer edge of a crown, inlay, onlay, 
or other restoration. The boundary surface of a 
tooth preparation and/or restoration is termed the 
finish line or finish curve. 

path of placement: the specific direction in which a 
prosthesis is placed on the abutment teeth. 

resistance form: the features of a tooth preparation 
that enhance the stability of a restoration and resist 
dislodgment along an axis other than the path of 
placement. 

retention form: the feature of a tooth preparation that 
resists dislodgment of a crown in a vertical direc- 
tion or along the path of placement. 

1. Zoellner A et al: Histobacteriology and pulp re- 
actions to long-term dental restorations, J Mar- 
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2. Langeland K, Langeland LK: Pulp reactions to 
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crown fixation, and permanent cementation, 

J Prosthet Dent 15:129, 1965. 

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Chapter 7 Principles of Tooth Preparation 



I 



7. Laforgia PD et al: Temperature change in the 
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I 



Section 2 Clinical Procedures-Part I 



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O'Connor RP et al: Effect of internal microblast- 
ing on retention of cemented cast crowns, J Pros- 
thet Dent 64:557, 1990. 

Saito C et al: Adhesion of polycarboxylate ce- 
ments to dental casting alloys, J Prosthet Dent 
35:543, 1976. 
Chan KC et al: Bond strength of cements to 

crown bases, j Prosthet Dent 46:297, 1981. 

DeWald JP et al: Crown retention: a comparative 
study of core type and luting agent. Dent Mater 
3:71, 1987. 
McComb D: Retention of castings with glass 

ionomer cement, J Prosthet Dent 48:285, 1982. 

Arfaei AH, Asgar K: Bond strength of three ce- 
ments determined by centrifugal testing, J Pros- 
thet Dent 40:294, 1978. 

Tjan AHL, Li T: Seating and retention of com- 
plete crowns with a new adhesive resin cement, 
j Prosthet Dent 67:478, 1992. 
el-Mowafy OM et al: Retention of metal ceramic 
crowns cemented with resin cements: effects of 
preparation taper and height, J Prosthet Dent 
76:524, 1996. 

Ayad ME et al: Influence of tooth surface 
roughness and type of cement on retention of 

complete cast crowns, J Prosthet Dent 77:116, 
1997. 

Jorgensen KD, Esbensen AL: The relationship 
between the film thickness of zinc phosphate ce- 
ment and the retention of veneer crowns. Acta 
Odontol Scand 26:169, 1968. 
Hembree JH, Cooper EW: Effect of die relief on 
retention of cast crowns and inlays, OperDent 
4:104, 1979. 

Gegauff AG, Rosenstiel SF: Reassessment of 
die-spacer with dynamic loading during cemen- 
tation, j Prosthet Dent 61:655, 1989. 
Carter SM, Wilson PR: The effect of die-spacing 
on crown retention, in t J Prosthod 9:21, 1996. 
Gibbs CH et al: Limits of human bite strength, 
J Prosthet Dent 56:226, 1986. 
Hegdahl T, Silness J: Preparation areas resisting 
displacement of artificial crowns, J Oral Rehabil 
4:201, 1977. 

Parker MH et al: New guidelines for preparation 
taper, J Prosthod 2:61, 1993. 
Wiskott HW et al: The effect of tooth preparation 
height and diameter on the resistance of com- 
plete crowns to fatigue loading, int J Prosthodont 
10:207, 1997. 



Chapter 7 Principles of Tooth Preparation 



■ 



82. 



83. 



84. 



85. 



87. 



Rosenstiel SF et al: Dental luting agents: a review 
of the current literature, J Prosthet Dent 80:280, 



Mesu FP: The effect of temperature on compres- 
sive and tensile strengths of cements, J Prosthet 
Dent 49:59, 1983. 

Branco R, Hegdahl T: Physical properties of 
some zinc phosphate and polycarboxylate ce- 
ments. Acta Odontol Scand 41:349, 1983. 
McLean JW: Polycarboxylate cements: five years' 
experience in general practice, Br Dent J 132:9, 
1972. 

Guyer SE: Multiple preparations for fixed 
prOSthodonticS, i Prosthet Dent 23:529, 1970. 
McLean JW: The science and art of dental ceramics, 

vol 1, Chicago, 1979, Quintessence Publishing, 

pl36. 

Wise MD: Stability of gingival crest after surgery 

and before anterior crown placement, J Prosthet 

Dent 53:20, 1985. 

Palomo F, Kopczyk RA: Rationale and methods 

for crown lengthening, J Am Dent Assoc 96:257, 

1978. 



90. Gorodovsky S, Zidan O: Retentive strength, dis- 
integration, and marginal quality of luting ce- 
ments, J Prosthet Dent 68:269, 1992. 

91. Wiskott HW et al: The relationship between 
abutment taper and resistance of cemented 
crowns to dynamic loading, int J Prosthod 9:117, 
1996. 

92. Mojon P et al: Maximum bond strength of denta 
luting cement to amalgam alloy, J Dent Res 
68:1545,1989. 

93. White SN, Yu Z: Compressive and diametral ter 
sile strengths of current adhesive luting agents, 

J Prosthet Dent 69:568, 1993. 

94. Kerby RE et al: Some physical properties of im- 
plant abutment luting cements, int J Prosthodont 
5:321, 1992. 

95. Cattani-Lorente M-A et al: Early strength of 
glass ionomer cements. Dent Mater 9:51, 1993. 

96. Miyamoto S et al: Study on fatigue toughness of 
dental materials. 1. Compressive strength on vai 
ious luting cements and composite resin cores, 

Nippon Hotetsu Shika Gakkai Zasshi 33:966, 1989. 



The Complete Cast 
Crown Preparation 



Although esthetic factors may Hmit its application, 
the all-metal complete cast crown should always be 
offered to patients requiring restoration for badly 
damaged posterior teeth. The complete cast crown 
has the best longevity of all fixed restorations. It can 
be used to rebuild a single tooth or as a retainer for 
a fixed partial denture (FPD). It involves all axial 
walls as well as the occlusal surface of the tooth be- 
ing restored (Fig. 8-1). 

Preparation for a complete cast crown requires 
that adequate tooth structure be removed to allow 
restoration of the tooth to its original contours. 
Tooth structure should be preserved when possible, 
but reduction should produce a crown of acceptable 
strength. 



significance when dealing with malaUgned teeth, al- 
though the extent of possible recontouring is lim- 
ited by periodontal considerations. Similarly, it is 
possible to allow better access to furcations for im- 
proved patient oral hygiene through recontouring 
of buccal and lingual walls (Fig. 8-2). When special 
requirements exist for axial contours, such as where 
retainers are needed for removable partial dentures, 
a complete crown is often the only restoration that 
will allow the necessary modifications for the cre- 
ation of properly shaped survey lines, guide planes, 
and occlusal rests (Fig. 8-3). (See Chapter 21.) 

The restoration permits easy modification of 
the occlusion, which is often difficult to accomplish 
if a more conservative restoration is made. This is 



ADVANTAGES 

Because all axial surfaces of the tooth are included 
in the preparation, the complete cast crown has 
greater retention than a more conservative restora- 
tion on the same tooth (e.g., a seven-eighths or 
three-quarter crown [see Fig. 7-32]). 

Normally a complete cast crown preparation also 
has greater resistance form than a partial- coverage 
restoration on the same tooth. For a partial veneer 
crown to rotate off the tooth, only the tooth struc- 
ture immediately lingual to the occlusal portion of 
the proximal groove or box need fail. However, if 
the axial walls of a complete cast crown have been 
prepared with the proper degree of taper or conver- 
gence, a significant amount of tooth structure must 
fail before the crown can be torqued off. 

The strength of a complete cast crown is superior 
to that of other restorations. Its cylinder-like config- 
uration encircles the tooth and is reinforced by a 
corrugated occlusal surface. Just as an O-shaped 
link in a chain resists deformation better than a 
C-shaped link, this restoration is less easily de- 
formed than its counterparts, which are more con- 
servative of tooth structure. 

A complete cast crown allows the operator to 
modify axial tooth contour. This can be of special 




Fig. 8- 1 . Complete cast crowns used to restore the molar 
teeth. The canines and premolars, which are more visible 
because of their more anterior arch position, have been re- 
stored with metal-ceramic crowns. 



202 



Chapter 8 The Complete Cast Crown Preparation 



I 




F i g . 8 -2 . Fluting of the axial walls of a molar complete 
cast crown (arrow) will allow better access to the furcation 
area for oral hygiene and will improve the long-term prog- 
nosis of the restoration. 




Fig. 8-3. Complete cast crowns used as retainers to ac- 
commodate a mandibular removable partial denture. 
Metal- ceramic crowns have been placed on the mandibular 
left canine (A) and the maxillary first molar (B). Note the 
occlusal rests (A, arrows) and the survey contours (B), 
which extend to form reciprocating guide planes. (See 
Chapter 21 .) 



especially important when supraerupted teeth are 
present or when the occlusal plane needs to be 
reestablished. 



DISADVANTAGES 

Because all coronal surfaces are involved in the 
preparation for a complete cast crown, removal of 
tooth structure is extensive and can have adverse ef- 
fects on the pulp and periodontium. Because of the 
proximity of the margin to the gingiva, it is not un- 
common to see inflammation of gingival tissues (al- 



though a properly fitting complete cast crown with 
good axial contour should minimize this). 

After cementation, it is no longer feasible to per- 
form electric vitality testing of an abutment tooth. 
The conductivity of the metal interferes with the 
test. This can be a disadvantage if future comphca- 
tions occur, although thermal tests occasionally will 
yield the necessary information. 

Patients may object to the display of metal asso- 
ciated with complete cast crowns, and in those with 
a normal smile line, the restoration may be re- 
stricted to maxillary molars and mandibular molars 
and premolars. 



ii]INDICATIONS 



The complete cast crown is indicated on teeth that 
exhibit extensive coronal destruction by caries or 
trauma. It is the restoration of choice whenever 
maximum retention and resistance are needed. On 
short clinical crowns or when high displacement 
forces are anticipated, such as for the retainer of a 
long-span FPD, grooves should be included as ad- 
ditional retentive features. 

This restoration is fabricated when correction of 
axial contours is not feasible with a more conser- 
vative technique. The restoration also may be used 
to support a removable partial denture, because 
obtaining the necessary contours with a partial- 
coverage restoration is more difficult. Although 
proximal guide planes can sometimes be prepared 
through simple enamel modification, arriving at 
properly incHned reciprocal guide planes and sur- 
vey contours is often impractical. The minimum di- 
mensions required for occlusal rests of an RPD 
framework necessitate removing significant amounts 
of enamel and, if the dentin is exposed, restoring the 
tooth with a cast crown.* 

The complete cast crown is indicated on en- 
dodontically treated teeth. Its superior strength 
compensates for the loss of tooth structure that re- 
sults from previous restorations, carious lesions, 
and endodontic access. 



^CONTRAINDICATIONS 



The complete cast crown is contraindicated if treat- 
ment objectives can be met with a more conserva- 
tive restoration. Wherever an intact buccal or lin- 
gual wall exists, use of a partial-coverage restoration 



*On mandibular premolars, a rest can sometimes be 
placed on top of the modified occlusal surface without 
interfering with the occlusion or articulation. 



I 



Section 2 Clinical Procedures-Part I 



should be considered. In particular, if less than max- 
imum retention and resistance are needed (e.g., on a 
short- span fixed partial denture), a preparation 
more conservative of tooth structure is called for. 
Similarly, if an adequate buccal contour exists or can 
be obtained through enamel modification (enamelo- 
plasty), a complete crown is not indicated. If a high 
esthetic need exists (e.g., anterior teeth), a complete 
cast crown is also contraindicated. 



^CRITERIA 

The occlusal reduction must allow adequate room 
for the restorative material from which the cast 
crown is to be fabricated: Type III or IV gold casting 
alloy or their low-gold content equivalent. Mini- 
mum recommended clearance is I mm on noncen- 
tric cusps and 1.5 mm on centric cusps. The occlusal 
reduction should follow normal anatomic contours 
to remain as conservative of tooth structure as pos- 
sible. Axial reduction should parallel the long axis 
of the tooth while allowing for the recommended 
6-degree taper or convergence between opposing 
axial surfaces. 

The margin should have a chamfer configuration 
and should ideally be located supragingivally. 
Sometimes crown lengthening is indicated to obtain 
a supragingival margin, rather than risk future peri- 
odontal disease (see Chapter 6). The chamfer should 
be smooth and distinct and allow for approximately 
0.5 mm of metal thickness at the margin. Typically it 
will be an exact replica of half the rotary instrument 
that was used to prepare it. (The recommended di- 
mensions for reduction are shown in Figure 8-4.) 




^ 0.5 mm 
^ 1 mm 



> 1.5 mm 



BUCCAL 



LINGUAL 



Fig. 8-4. Recommended dimensions for a complete cast 
crown. On functional cusps (buccal mandibular and lingual 
maxillary) the occlusal clearance should be equal to or 
greater than 1.5 mm. On nonfunctional cusps, a clearance of 
at least 1 mm is needed. The chamfer should allow for ap- 
proximately 0.5 mm of metal thickness at the margin. 



SPECIAL CONSIDERATIONS 

Functional (Centric) Cusp Bevel. Proper tooth 
preparation for a complete cast crown will result in 
the reduction being directly beneath the cusps of the 
crown (see Fig. 7-43). This is important for ensuring 
optimum restoration contour with maximum dura- 
bility and conservation of tooth structure. Proper 
placement of the functional cusp bevel will achieve it. 
Because additional reduction is needed for the func- 
tional cusps (to give 1.5 mm of occlusal clearance), the 
bevel must be angled flatter than the external surface 
(Fig. 8-5). On most teeth the functional cusp bevel 
will be placed at about 45 degrees to the long axis. 

Nonfunctional (Noncentric) Cusp Bevel. AH 

complete crown preparations should be assessed for 
adequate reduction at the occlusoaxial line angles of 
the nonfunctional cusps. A minimum of 0.6 mm of 
clearance is needed here for adequate strength. 
Maxillary molars in particular often require an ad- 
ditional reduction bevel in this area (Fig. 8-6). With- 
out it, an overcontoured restoration that does not 
follow normal configuration may result. Such addi- 
tional reduction is often unnecessary for mandibu- 
lar molars, however, because they are lingually in- 
clined and their profile is relatively straight. 




Fig. 8-5. The functional cusp bevel is prepared by slant- 
ing the bur at a flatter angle than the cuspal angulation. This 
will ensure additional reduction for the functional cusp. 



LINGUAL 




BUCCAL 



Fig. 8-6. The configuration of the facial wall of the max- 
illary molars may require slight additional reduction in the 
occlusal third to prevent an overcontoured restoration. 



Chapter 8 The Complete Cast Crown P rpparation 



I 



Chamfer Width. Increasing the faciohngual 
width of a complete crown is a common fault in 
practice and is a leading cause of periodontal dis- 
ease associated with restorations. Adequate cham- 
fer width (minimum 0.5 mm) is important for 
developing optimum axial contour. However, on 
small premolars it may be advantageous to prepare 
a slightly narrower chamfer to conserve tooth 
structure and retention form. This requires increas- 
ingly careful manipulation of the wax pattern dur- 
ing fabrication of the restoration and careful assess- 
ment to ensure that the crown is not excessively 
contoured. 



^PREPARATION 

The clinical procedure to prepare a tooth for a com- 
plete cast crown consists of the following steps: 

Occlusal guiding grooves 

Occlusal reduction 

Axial alignment grooves 

Axial reduction 

Finishing and evaluation 

Armamentarium (Fig. 8-7 and Table 8-1) 

STEP-BY-STEP PROCEDURE 

The tooth preparation steps have been illustrated 
for a mandibular second molar. Depending on the 
tooth to be prepared (e.g., a premolar versus a mo- 
lar) the exact number of guiding grooves may vary. 
The recommended sequence remains identical, 
however. 

Guiding Grooves for Occlusal Reduction. A 

tapered carbide or a narrow, tapered diamond is 
recommended to place the guiding grooves for oc- 
clusal reduction.* 

1. Place depth holes approximately 1 mm deep 
in the central, mesial, and distal fossae and 
connect them so that a channel runs the 
length of the central groove and extends into 
the mesial and distal marginal ridge. 

2. Place guiding grooves in the buccal and lin- 
gual developmental grooves and in each tri- 



*The use of guiding grooves for occlusal reduction is 
helpful only if the tooth is in good occlusal relationship 
before preparation. On most teeth this can be achieved 
with a foundation restoration and is done as part of the 
mouth preparation phase of treatment. Where this is not 
practical (e.g., when correcting occlusal discrepancies or 
replacing existing crowns), a matrix is made from the 
diagnostic waxing procedure, and this is used to assess 
optimal reduction (see Fig. 15-14, A). 



angular ridge extending from the cusp tip to 
the center of its base (Figs. 8-8 and 8-9). 
3. Because the centric or functional cusp is to be 
protected by an adequate thickness of metal. 



L 



teritanum 



Instrument 



Tapered carbide bur 
or diamond 

Narrow, round-ttpped, 
tapered diamond 
(regular grit) (0.8 mm) 

Wide, round-tipped, tapered 

diamond (fine grit)' 

(1.2 mm) 
Utilily wox and wax caliper 
Occlusal reduction gauge 
High- and low-speed friction 

grip centra-angles 



TABLE 8- 1 

Occlusal guiding grooves 
Additional retentive features 
Occlusal reduction 
Axial alignment grooves 
Axial reduction 
Chamfer preparation 
Finishing 



Verification of occlusal 
clearance 




Fig. 8-7. Armamentarium for the complete cast crown 
preparation. 




Note that the 
grooves are deeper 
for tlie functionaJ 
cusp. 



Fig. 8-8. Guiding grooves are placed on the occlusal sur- 
face. They are deeper on the functional cusp, and for the 
functional cusp bevel they diminish in depth from the cusp 
tip to the cervical margin. 



I 



Section 2 Clinical Procedures-Part I 




Fig. 8-9. A, A complete cast crown is indicated on this 
mandibular second molar with occlusal, proximal, and cer- 
vical lesions as well as a buccal longitudinal fracture. B, Ini- 
tial depth grooves placed for occlusal reduction. Note that 
they have not yet been extended onto the buccal surface, 
where the functional cusp bevel will be placed. 



place a functional cusp bevel to ensure this in 
the area of contact with the opposing tooth. 
The depth of this guiding groove should be 
slightly less than 1.5 mm (to allow for smooth- 
ing) in the area of the centric stop, and it should 
gradually diminish in a cervical direction. 
4. Use the guiding grooves to ensure that oc- 
clusal reduction follows anatomic configura- 
tion and thus minimizes the loss of tooth 
structure while ensuring adequate reduction, 
as dictated by the mechanical properties of 
the alloy from which the restoration is to be 
fabricated. The guiding grooves must be 
placed with accuracy; the practitioner should 
concentrate on the position, depth, and angu- 
lation of each groove. A groove should be 
placed in the low point and high point of 
each cusp. The low points are the central and 
developmental grooves; the high points are 
the cusp tips and triangular ridges. Correct 
depth (0.8 mm* for the central groove and 
nonfunctional cusps, 1.3 mm* for the func- 
tional cusps) is achieved by knowledge of the 



*Allowing 0.2 mm for smoothing the preparation. 




Half of the occlusal reduction 
is performed; the other half is 
maintained for reference 
purposes. 



Fig. 8-1 0. After the guiding grooves are placed, the oc- 
clusal reduction is performed. Either the mesial or the dis- 
tal half is maintained initially as a reference. 



instruments being used. The practitioner 
should memorize the diameters of the rotary 
instruments; this will facilitate assessing the 
adequacy of the reduction in progress. If nec- 
essary, a periodontal probe can be used to 
measure the extent of reduction. Correct an- 
gulation of the grooves is needed to ensure 
that the occlusal reduction is correctly situ- 
ated beneath the occlusal surface of the 
restoration. On the nonfunctional cusp, the 
groove should parallel the intended cuspal 
inclination; on the functional cusp, it should 
be angled slightly flatter to ensure the addi- 
tional reduction of the functional cusp. 

Occlusal Reduction. Once the guiding grooves 
have been deemed satisfactory, the tooth structure 
that remains between the grooves is removed with 
the carbide or the narrow, round-end, tapered dia- 
mond. Proper placement of the grooves automati- 
cally results in adequate occlusal clearance. 

5. Complete the occlusal reduction in two steps 
(Fig. 8-10). Half the occlusal surface is re- 
duced first so that the other half can be main- 
tained as a reference. When the necessary 
reduction of the first half has been accom- 
plished, reduction of the remaining half can 
be completed (Fig. 8-11). 

6. On completion, check that a minimum clear- 
ance of 1.5 mm has been established on func- 
tional cusps and at least 1.0 mm on nonfunc 
tional cusps. This clearance must be verified 



Chapter 8 The Complete Cast Crown Preparation 



I 




Fig. 8-1 1 . A, Note the angulation of the bur as the func- 
tional cusp bevel is placed. B, Completed occlusal reduc- 
tion. Note that it follows normal occlusal form. Three dis- 
tinct planes can be seen buccolingually. 




A 



Fig. 8-1 2. Evaluation of the adequacy of occlusal clear- 
ance. A, The patient closes into softened wax. B, The thick- 
ness of the wax is assessed visually and measured with a 
wax caliper after it has been removed from the mouth. 



in all excursive movements that the patient 
can make. The patient should close into sev- 
eral layers of dark-colored utility wax in 
maximum intercuspation (Fig. 8-12). 

7. Remove the wax from the mouth and evalu- 
ate it for thin spots, which can be measured 
with a wax caliper. 

8. Place the wax back in the patient's mouth 
and have the patient move the mandible into 
protrusive and excursive positions. On re 
moval, the thickness of the utility wax is 
again measured, this time to verify that ade- 
quate clearance exists in the dynamic range 
as well as the intercuspal position. A conve- 
nient alternative is to use an occlusal reduc- 
tion gauge* (Fig 8-13). 

Alignment Grooves for Axial Reduction. After 
the occlusal reduction is completed, three alignment 
grooves are placed in each buccal and lingual wall 
with a narrow, round-end, tapered diamond. One is 
placed in the center of the wall, and one in each 
mesial and distal transitional line angle (Fig. 8-14). 

1. When these guiding grooves are placed, be 
sure that the shank of the diamond is parallel 



*Thompson Dental Mfg. Co., Inc: Missoula, Montana. 




Fig. 8-1 3. Occlusal clearance can be judged intraorally 
with a reduction gauge. This instrument has 1-mm- and 
1.5-mm-diameter spherical tips. 



to the proposed path of withdrawal of the 
restoration. This automatically produces a 
convergence between the axial walls of the 
alignment grooves that is identical to the 



I 



Section 2 Clinical Procedures-Part I 



r 




When placing these 
grooves^ keep reduction 
to a minimum at the tip 
of the diamond. 



Fig -1 . Alignment grooves for axial reduction are 
placed in the buccal and lingual surfaces parallel to the 
long axis of the tooth buccolingually and mesiodistally. 



taper of the diamond. If a diamond with a 6- 
degree taper is used, an identical axial con- 
vergence on the preparation wall will result. 

2. Do not let the diamond cut into the tooth be- 
yond the point where its tip is buried in tooth 
structure up to the midpoint; otherwise, a lip 
of unsupported tooth enamel will be created 
(see Fig. 7-21). Gingivally the resulting depth 
of the alignment grooves therefore should be 
no more than one half the width of the tip of 
the diamond. Occlusocervically, the place- 
ment of the tip of the instrument will deter- 
mine the location of the margin (Fig. 8-15). 

3. Note that the alignment grooves determine 
the path of withdrawal of the restoration. 
They should be placed parallel to the pro 
posed path of withdrawal, typically the long 
axis of the tooth. 

4. Use a periodontal probe to assess the relative 
parallelism of the alignment grooves with one 
another or with the proposed path of with 
drawal, of a secondary retainer if the prepared 
tooth is to serve as a fixed partial denture 
abutment. When uncertainty exists regarding 
the correct placement of alignment grooves 
(as is likely on long- span fixed partial denture 
abutments), making an impression with irre- 
versible hydrocolloid (alginate) is especially 
helpful. This can be poured in rapid-setting 
stone, and the resulting cast can be analyzed 




Fig- -1 .A, The diamond is aligned parallel to the long 
axis of the tooth as the buccal guiding grooves for axial 
alignment are placed. B, After all six grooves have been 
placed. Note that they are deep occlusally but shallower to- 
ward the cervical margin. 



with a dental surveyor.* At this time, correc- 
tions may still be easily made before unneces- 
sary tooth reduction has occurred. 

Axial Reduction. The technique for axial reduc 
tion is similar to that for occlusal reduction. The 
remaining islands of tooth structure between the 
alignment grooves are removed while the chamfer 
margin is being placed, and the same narrow, 
round-tipped diamond is used for the procedure 
(Figs. 8-16 and 8-17). 

5. As with the occlusal reduction, perform the 
axial reduction for half the tooth at a time, 
maintaining the other half as a reference for 
assessing adequacy of the preparation. 

6. Pay special attention to the interproximal .ar- 
eas to prevent unintentional damage to the 
adjacent teeth. This often results if the practi 
tioner is impatient and attempts to force the 
diamond into the area. Sufficient time must 
be allowed for the cutting instrument to cre- 
ate its own space (Fig. 8-18). Typically, if the 



*The same cast can be used to fabricate the provisional 
restoration (see Chapter 15). 



Chapter S The rnmplete Cast rrown Preparation 



I 




Fig. 8-16. If axial reduction is completed first on either 
the distal or the mesial half of the tooth, evaluation is sim- 
pUfied because the remaining intact tooth can serve as a 
reference. 





Fig. 8-1 8. A, As the mesiobuccal axial reduction is per- 
formed, a cervical chamfer is placed. B, Make the chamfer 
of relatively even width and maintain the somewhat angu- 
lar preparation outline form to maximize resistance form. 




Fig. 8-17. A, Note the alignment of the diamond as 
tooth structure between the aUgnment grooves is removed. 
B, Axial reduction. The distobuccal axial reduction has been 
completed. 



proper cervical placement of the margin has 
been selected with proper axial alignment of 
the instrument, a lip of tooth enamel will be 
maintained between the diamond and the 
adjacent tooth that protects it from any dam- 
age (Fig. 8-19). 
7. If desired, protect the adjacent teeth by plac- 
ing a metal matrix band. The most difficult 



Fig. 8-1 9. A lip of enamel (arrow) protects the adjacent 
tooth from iatrogenic damage as the axial reduction is 
completed. 



interproximal areas to reduce are those with 
significant buccolingual dimension and those 
with root proximity. Typically, however, the 
critical area will be only a few millimeters in 
length. 

Cut into the proximal area from both sides 
until only a few millimeters of interproximal 
island remain (Fig. 8-20). This area can then 
be removed and contact broken by using 
thinner, tapered diamonds. If the adjacent 
proximal surface is damaged, it must be 



I 



Section 2 Clinical Procedures-Part I 




A 




>0.6 mm 



>0.6 mm 



Fig. 8-21 . A, Note that adequate clearance (? 0.6 mm) 
exists between the external surface of the proximal chamfer 
and the adjacent tooth. B, Occlusal view of the preparation. 



As the axial reduction is performed, 
eventually a small island of tooth 
structure will remain in the inter- 
proximal area. When removing this, 
maintain a narrow "lip" of tooth 
Structure between the diamond and 
the adjacent tooth to protect the 
latter from damage. 



Fig. 8-20. Preparation of the proximal contact area. 



polished with white stones, silicone points, 
and prophylaxis paste before impression 
making. Ideally a fluoride application should 
be given for improved resistance and to pre- 
vent demineralization of the surface enamel. 
9. Place the cervical chamfer concurrently with 
axial reduction. Its width should be approxi- 
mately 0.5 mm, which will allow adequate 
bulk of metal at the margin. This chamfer 
must be smooth and continuous mesiodis- 
tally, and a distinct resistance against vertical 
displacement should be detected when 
probed with the tip of an explorer (Fig. 8-21). 
Unsupported enamel cannot be tolerated be- 
cause it is likely to fracture when the restora- 
tion is tried in or cemented, which will result 
in an open margin and early failure of the 
restoration. 

Finishing. A smooth surface finish and conti- 
nuity of all prepared surfaces will aid most phases 
of fabrication of the restoration. Smooth transi- 
tions from occlusal to axial surfaces facilitate im- 
pression making, waxing, investing, and casting be- 
cause bubble formation is reduced (Fig. 8-22). 
1. Use a fine-grit diamond or carbide bur of 
slightly greater diameter for finishing the 
chamfer margin. This should be done as 




A 



Fig. 8-22. A, The transition from lingual to occlusal is 
rounded with a fine-grit diamond. B, All sharp line angles 
between occlusal reduction and functional cusp bevel are 
similarly rounded. C, The margin is refined, and any minor 
irregularities are removed. 



smoothly as possible, with the handpiece op- 
erating at reduced speed. NOTE: Some prac- 
titioners favor using a low-speed contraangle 
for the finishing. A properly finished margin 
should be glassy smooth when touched by 
the tine of an explorer. 
2. Finish all prepared surfaces and slightly 
round all line angles. If necessary, place a 



Chapter 8 The Complete Cast Crown Preparation 



I 




Fig. 8-23. Completed preparation. The carious lesions 
have been excavated and the resulting irregularities 
blocked out with amalgam. A, Buccal appearance. 
B, Occlusal appearance. 



nonfunctional cusp bevel at this time (Fig. 
8-23). During finishing of the chamfer, the use 
of air cooling alone is recommended to im- 
prove visibility. However, when only air cool- 
ing is used, a water spray should be applied 
from time to time to prevent the tooth from 
dehydrating, and the possible development 
of pulpal damage, as well as to wash away 
debris. The wider diamond is recommended 
because it will smooth out any unwanted rip- 
ples that may have been created during axial 
reduction and will eliminate any unsup- 
ported enamel at the margin. 
3. Place additional retentive features as needed 
(e.g., grooves or boxes) with the tapered car- 
bide bur (Fig. 8-24). 
The criteria used to determine the need for such 
features to enhance retention and resistance are de- 
scribed in Chapter 7. 

Evaluation. Upon completion, the preparation 
is evaluated to assess whether all the criteria have 
been fulfilled (Fig. 8-25). 

One of the more common errors in complete cast 
crown preparations is overtapering of the opposing 
axial walls. This significantly reduces the retention 
of the completed restoration. If a tooth preparation 
has been inadvertently overreduced through exces- 





Fig. 8-24. A, When opposing axial walls are excessively 
tapered, internal features such as this buccal groove can be 
used to improve retention and resistance form. B, Mesially 
tipped molars and short premolars often benefit from 
grooves and/or boxes incorporated in the preparation 
design. 




Fig. 8-25. The completed preparation is characterized 
by a smooth, even chamfer; a 6-degree taper; and gradual 
transitions between all prepared surfaces. 



sive tapering of axial walls, it should be carefully 
evaluated to determine how it can be corrected. If a 
band of several millimeters of tooth structure can 
be prepared circumferentially with a restricted ta- 
per of approximately 6 degrees, it is probably un- 
necessary to modify the preparation further to 



I 



Section 2 Clinical Procedures-Part I 



compensate for areas of excessive reduction in the 
occlusal third. If this is not the case, an approach 
slightly less conservative of tooth structure may be 
warranted: (1) uprighting overtapered axial walls 
to obtain the mechanical advantage of increased re- 
tention or (2) using grooves, boxes, or pinholes as 
needed. 

No undercuts between any opposing axial walls 
can be accepted. When the diamond is placed 
against the axial surface of the prepared tooth, par- 
allel to the path of withdrawal, it should be possible 
to move the instrument around the tooth so the en- 
tire height of the preparation is touching the dia- 
mond at all times. The tip of the diamond should 
rest on the chamfer throughout this movement, and 
no light should be visible between the instrument 
and the axial surface. 

Finally, occlusal and proximal clearances are as- 
sessed. They should be adjusted if inadequate pro- 
vision has been made for the restorative material. 
Any problems must be corrected before provision- 
alization (Fig. 8-26) and impression making. 



i|] SUMMARY 



The complete cast crown, an all-metal restoration 
often used on single posterior teeth as a retainer for 
a fixed partial denture, provides greater retention 
and resistance than any other type of restoration. It 
is not indicated for every restorative circumstance, 
however. It is unnecessary if the buccal and/or lin- 
gual walls of a tooth are intact or if less than maxi- 
mum retention is needed. The rather extensive re- 
moval of tooth structure required in its preparation 
can have adverse pulpal and periodontal effects. Its 
high strength makes it especially suitable for restor- 
ing an endodontically treated tooth, although in pa- 
tients who find visible metal a significant drawback, 
the metal-ceramic or a more conservative partial- 
coverage restoration may be preferred. 

A well-organized approach to preparation for a 
complete cast crown should be based on the selec- 
tive use of guiding grooves of predetermined depth 
correlated with specific properties of the restorative 
material. Adequate occlusal reduction is necessary. 



A 




Fig. 8-26. A, Acrylic resin provisional restoration is ce- 
mented. B, Complete cast crown is cemented. 



following the normal anatomic tooth contours, and 
the axial reduction should also conform to the nor- 
mal configuration of the tooth, with minimum taper 
(6 degrees). Under no circumstances should under- 
cuts remain in the proximal walls. These must be re- 
moved by additional tooth preparation or blocked 
out with a suitable base material. The chamfer is the 
margin of choice for a complete cast crown. It 
should be distinct and of adequate width. No un- 
supported enamel can be permitted. Occlusocervi- 
cally, the margin should be supragingival, and it 
should be smooth and continuous mesiodistally. 
When assessing the adequacy of the chamfer, one 
should be able to feel distinct resistance against ver- 
tical displacement by an explorer or periodontal 
probe. 



Chapter 8 The Complete Cast Crown Preparation 



I 



dy Q^ic^ihfit 



1 . What are the indications and central ndicatf on s for compiete cast crowns? 

2. What are the advantages and disadvantages of complete cast crowns? 

3. What is Jhe recominended armamentanum, and in what sequence should a mandibular molar be pre- 
pared, for a complete cast crown? 

4. What are the minimum criteria for each step described in question 3? 




Section 2 Clinical Procedures-Part I 



E 



UMMABYCHAliT 



Indications 



Contraindic ati ons 



Extensive destrLfctron from caries 
or trauma 

Endodonticot!/ treated teetli 

Existing restoration 

Necessity for maximum retention 
and strength 

To provide contours to receive a 
removable appliance 

Other reconfouring of oxial sur- 
faces (minor corrections of 
molindinations) 

Correction of occlusal plane 



Less than moximunfi retention 
necessary 

Esthettcs 



Advantages 

Strong 

High retentive qualities 

Usually easy to obtoin ade- 
quate resistance form 

Option to modify form and 
occlusion 



Disadvantages 



Removal of large amount of 
tooth structure 

Adverse effects on tissue 

Vitality testing not readily 
feasible 

Display of metal 



Chapter 8 The Comple Ic Cast Crown Preparation 



I 



Complete Cast Crown 


Preparation Steps 


Recommended Armamentarium 


Criteria 


Depth grooves for occlusal 
reduction 


Tapered carbide or diamond 


Minimum clearance on noncenfric cusps: 1 mm 
Minimum clearance on centric cusps: 1 .5 mm 


Functional cusp bevei 


Same 


Flatter than cuspal plane, to allow additional reduc- 
tion at functionat cusp 


Occlusol reduction (half at a 
Hme) 


Regular-grit, round-tipped, 
tapered diamond 


should follow normal anotomic configuration of oc- 
clusal surface 


Alignment grooves for axial 
recluction 


Same 


Chamfer allows 0.5 mm of thickness of wax at 
margins 


Axial reduction (half at a 
lime} 


Same 


Reduction performed parallel to long axis 


Finishing of chamfer 


Wide, round-tipped dia- 
mond or carbide 


Smooth mesiodrstally and buccolinguoKy; resistar^ce 
to vertical displacement b/ tip of explorer or pen- 
odontal probe 


Additional retentive features 
if needed 


Tapered carbide 


Grooves, boxes, pinholes as described for partial- 
coverage restorations 


Finishing 


Fine-grit diamond or 
carbide 


Rounding of all shorp line angles to facilitote impres- 
sion making, die pouring, waxing^ and casting 



i;.ilifti!'!i-f!!i 



^;5il:=;^.';';?'iiiifife'!^^ 




CHAPTER 



HE Metal-Ceramic 
Crown Preparation 



In many dental practices the metal-ceramic crown is 
one of the most widely used fixed restorations. This 
has resulted in part from technologic improvements 
in the fabrication of restoration by dental laborato- 
ries and in part from the growing amount of cos- 
metic demands that challenge dentists today. 

The restoration consists of a complete -coverage 
cast metal crown (or substructure) that is veneered 
with a layer of fused porcelain to mimic the appear- 
ance of a natural tooth. The extent of the veneer can 
vary. 

To be successful, a metal-ceramic crown prepara- 
tion requires considerable tooth reduction wherever 
the metal substructure is to be veneered with dental 
porcelain. Only with sufficient thickness can the 
darker color of the metal substructure be masked 
and the veneer duplicate the appearance of a nat- 
ural tooth. The porcelain veneer must have a certain 
minimum thickness for esthetics. Consequently, 
much tooth reduction is necessary, and the metal- 
ceramic preparation is one of the least conservative 
of tooth structures (Fig. 9-1). 

Historically, attempts to veneer metal restora- 
tions with porcelain had several problems. A major 
challenge was the development of an alloy and a ce- 
ramic material with compatible physical properties 
that would provide adequate bond strength. In ad- 
dition, it was initially difficult to obtain a natural 
appearance. 

The technical aspects of the fabrication of this 
restoration are discussed more in Chapter 24. For 
now, only a brief description is provided. The metal 
substructure is waxed and then cast in a special 
metal-ceramic alloy having a higher fusing range 
and a lower thermal expansion than conventional 
gold alloys. After preparatory finishing procedures, 
this substructure, or framework, is veneered with 
dental porcelain. The porcelain is fused onto the 
framework in much the same manner as household 
articles are enameled. Modern dental porcelains 
fuse at a temperature of about 960° C (1760° F). Be- 
cause conventional gold alloys would melt at this 
temperature, the special alloys are necessary. 



To ensure good 
esthetics, substantial 
tooth reduction is 
necessary. 



Facial 



^0,5 mm 
^03 mm 

> 1.2 mm 

^1.5 mm 



Buccal 
^03 mm 
^1,2 mm 



13-1.7 mm 




Lingual 



^0.6 mm 



1.3-17 mm 



G.8'1.2 mm 



Fig. 9- 1 . Recommended minimum dimensions for a 
metal-ceramic restoration on an anterior tooth (A) and a 
posterior tooth (B). Note the significant reduction needed 
compared to that for a complete cast or partial veneer 
crown. 



^INDICATIONS 

The metal-ceramic crown is indicated on teeth that 
require complete coverage, where significant es- 
thetic demands are placed on the dentist (e.g., the 
anterior teeth). It should be recognized, however, 
that, if esthetic considerations are paramount, an 
all-ceramic crown (see Chapters 1 1 and 25) has dis- 
tinct cosmetic advantages over the metal-ceramic 
restoration; nevertheless, the metal-ceramic crown 
is more durable than the all-ceramic crown and gen- 
erally has superior marginal fit. Furthermore, it can 



216 



Chapter 9 The Metal-Ceramic Crown Preparation 



I 



serve as a retainer for a fixed partial denture be- 
cause its metal substructure can accommodate cast 
or soldered connectors. Whereas the all-ceramic 
restoration cannot accommodate a rest for a remov- 
able prosthesis, the metal-ceramic crown may be 
successfully modified to incorporate occlusal and 
cingulum rests as well as milled proximal and reci- 
procal guide planes in its metal substructure (see 
Chapter 21). 

Typical indications are similar to those for 
all-metal complete crowns: extensive tooth destruc- 
tion as a result of caries, trauma, or existing previ- 
ous restorations that precludes the use of a more 
conservative restoration; the need for superior re- 
tention and strength; an endodontically treated 
tooth in conjunction with a suitable supporting 
structure (a post-and-core); and the need to recon- 
tour axial surfaces or correct minor malinclinations. 
Within certain limits this restoration can also be 
used to correct the occlusal plane. 



^CONTRAINDICATIONS 

Contraindications for the metal-ceramic crown, as 
for all fixed restorations, include patients with ac- 
tive caries or untreated periodontal disease. In 
young patients with large pulp chambers, the 
metal-ceramic crown is also contraindicated be- 
cause of the high risk of pulp exposure (see Fig. 
7-4). If at all possible, a more conservative restora- 
tive option such as a composite resin or porcelain 
laminate veneer (see Chapter 25) is preferred. 

A metal-ceramic restoration should not be con- 
sidered whenever a more conservative retainer is 
feasible, unless maximum retention is needed-as 
for a long- span FPD. If the facial wall is intact, the 
practitioner should decide whether it is truly neces- 
sary to involve all axial surfaces of the tooth in the 
proposed restoration. Although perhaps technically 
more demanding and time consuming, a more con- 
servative solution usually can be found to satisfy 
the patient's needs that may provide superior 
long-term service. 

^] ADVANTAGES 

The metal-ceramic restoration combines, to a large 
degree, the strength of cast metal with the esthetics 
of an all-ceramic crown. The underlying principle is 
to reinforce a brittle, more cosmetically pleasing 
material through support derived from the stronger 
metal substructure. Natural appearance can be 
closely matched by good technique and if desired 
through characterization of the restoration with in- 
ternally or externally applied stains. Retentive qual- 



ities are excellent because all axial walls are in- 
cluded in the preparation, and it is usually quite 
easy to ensure adequate resistance form during 
tooth preparation. The complete-coverage aspect of 
the restoration permits easy correction of axial form. 
In addition, the required preparation often is much 
less demanding than for partial-coverage retainers. 
Generally, the degree of difficulty of a metal- 
ceramic preparation is comparable to that of prepar- 
ing a posterior tooth for a complete cast crown. 

DISADVANTAGES 

The preparation for a metal-ceramic crown requires 
significant tooth reduction to provide sufficient 
space for the restorative materials. To achieve better 
esthetics, the facial margin of an anterior restoration 
is often placed subgingivally, which increases the 
potential for periodontal disease. However, a 
supragingival margin can be used if significant 
cosmetic concerns do not prohibit it or if the restora- 
tion incorporates a porcelain labial margin (see 
Chapter 24). 

Compared to an all-ceramic restoration, the 
metal-ceramic crown may have slightly inferior es- 
thetics, but it can be used in higher- stress situations 
or on teeth that would not provide adequate sup- 
port for an all-ceramic restoration. 

Because of the glasslike nature of the veneering 
material, a metal-ceramic crown is subject to brittle 
fracture (although such failure can usually be attrib- 
uted to poor design or fabrication of the restoration). 
A frequent problem is the difficulty of accurate shade 
selection and of communicating it to the dental ce- 
ramist. This is often underestimated by the novice. 
Since many procedural steps are required for both 
metal casting and porcelain application, laboratory 
costs generally place the metal-ceramic restoration 
among the more expensive of dental procedures. 

PREPARATION 

The recommended sequence of preparation is illus- 
trated for a maxillary right central incisor (Fig. 9-2); 
however, the same step-by-step approach can be ap- 
plied to other teeth (Fig. 9-3). As with all tooth 
preparations, a systematic and organized approach 
to tooth reduction will save time. 

Armamentarium (Fig. 9-4). The instruments 
needed to prepare teeth for a metal-ceramic crown 
include: 

• Round-tipped rotary diamonds (regular grit 
for bulk reduction, fine grit for finishing) or 
carbides 



I 



Section 2 Clinical Procedures -Part I 




M,N 



Fig. 9-2. Preparation of a maxillary incisor for a metal-ceramic crown. A, Heavily restored maxillary 
central incisor. B and C, Rotary instrument aligned with the cervical one third and incisal two thirds to 
gauge correct planes of reduction. D and E, Guiding grooves placed in the two planes. The cervical 
groove is made parallel to the path of withdrawal, which usually coincides with the long axis of the 
tooth. The incisal depth groove is prepared parallel to the facial contour of the tooth. F and G, Incisal 
guiding grooves are placed. H, Incisal edge reduction. I to K, Facial reduction accomplished in two 
planes. L, Breaking proximal contact, maintaining a lip of enamel to protect the adjacent tooth from in- 
advertent damage. M and N, Proximal reduction. O, Placing a 0.5-mm lingual chamfer. 



rhapter Q The Metal-rerannic rrown Preparation 



I 



P,Q 




SJ 





Fig. 9-2, cont'd. P, A 
football-shaped diamond is rec- 
ommended for lingual reduction 
of anterior teeth. Alternatively, a 
wheel- shaped diamond may be 
used. Q to S, Finishing the prepa- 
ration with a fine-grit diamond. 
T, The completed preparation. 




Fig. 9-3. Preparation of a maxillary premolar for a metal-ceramic crown. A, Depth holes. B, Occlusal 
depth cuts. C, Half of the occlusal reduction is completed. D, Occlusal reduction is complete. Guiding 
grooves are placed for axial reduction. E and F, Lingual chamfer and facial shoulder are prepared on half 
the tooth. G, Completed preparation. 

(A to E, Lingual view; F and G, buccal view.) 



I 



Section 2 Clinical Procedures-Part I 




Fig. 9-4. Armamentarium for the metal-ceramic crown 
preparation. 



• Football- or wheel- shaped diamond (for lin- 
gual reduction of anterior teeth) 

• Flat-ended, tapered diamond (for shoulder 
preparation) 

• Finishing stones 

• Explorer and periodontal probe 

• Hatchet and chisel 

The actual sequence of steps can be varied 
slightly depending on operator preference. 

Step-By-Step Procedure. The preparation is 
divided into five major steps: guiding grooves, in- 
cisal or occlusal reduction, labial or buccal reduc- 
tion in the area to be veneered with porcelain, axial 
reduction of the proximal and lingual surfaces, and 
final finishing of all prepared surfaces. 

Guiding Grooves 

1. Place three depth grooves (Fig. 9-5), one in 
the center of the facial surface and one each 
in the approximate locations of the mesiofa 
cial and distofacial line angles (see Fig. 9-2, A 
to E). These will be in two planes: the cervical 
portion to parallel the long axis of the tooth, 
the incisal (occlusal) portion to follow the 
normal facial contour (see Fig. 9-2, D and E). 

2. Perform the facial reduction in the cervical 
and incisal planes. The cervical plane will de- 
termine the path of withdrawal of the com- 
pleted restoration. The incisal or occlusal 
plane will provide the space needed for the 
porcelain veneer; it should be approximately 
1.3 mm deep to allow for additional reduc- 
tion during finishing. The incisal grooves 
usually extend halfway down the facial sur- 
face, although (depending on the shape of the 
tooth) they may extend to include the incisal 
two thirds. Cervical grooves are generally 
made parallel to the long axis of the tooth. 
However, they can be adjusted slightly to cre- 
ate a more desirable path of withdrawal; in 
particular, some labial inclination will im- 




Fig. 9-5. Depth grooves in the facial wall are placed in 
two directions: incisally, parallel to the tooth contour; cervi- 
cally, parallel to the path of withdrawal. The grooves 
should be 1.3 mm deep. 



prove retention on a tooth with little cingu- 
lum height. On small teeth it may be advis- 
able to keep the cervical grooves somewhat 
shallower near the margin. 
3. Place three depth grooves (about 1.8 mm 
deep) in the incisal edge of an anterior tooth. 
This will provide the needed reduction of 2 
mm and allow finishing (see Fig. 9-2, F and 
G). Verify the depth of these grooves can be 
verified with a periodontal probe. On poste- 
rior teeth where the occlusion is to be estab- 
lished in porcelain, 2 mm of clearance must 
exist. If the occlusion is to be established in 
metal, the same minimum clearances are 
needed as for a complete cast crown. Poste- 
rior occlusal reduction incorporates a func- 
tional cusp bevel on the lingual cusp, similar 
to that for a complete cast crown. When ini- 
tially positioning the diamond for anterior 
teeth, it may be helpful to observe the long 
axis of the opposing tooth in the intercuspal 
position and to orient the instrument perpen- 
dicular to that (Fig. 9-6). The grooves must 
not be too deep; otherwise, an overreduced 
and undulating surface will result. 

Incisal (Occlusal) Reduction. The completed 
reduction of the incisal edge on an anterior tooth 
should allow 2 mm for adequate material thickness 
to permit translucency in the completed restoration. 
Posterior teeth generally require less (1.5 mm) be- 
cause esthetics is not as critical. Caution must be 
used, however, because excessive occlusal reduc- 
tion shortens the axial walls and thus is a common 
cause of inadequate retention and resistance form in 



Chapter 9 The Metal-Ceramic Crown Prepar atmu 



I 




Fig. 9-6. A, Depth grooves 1.8 mm deep placed in the incisal edges to ensure adequate and even re- 
duction. B, Incisal reduction completed on the left central and lateral incisors. Note the angulation of the 
diamond, perpendicular to the direction of loading by the mandibular anterior teeth. 



the completed preparation. This can be particularly 
problematic on anterior teeth (where as a conse- 
quence of tooth form, most of the retention is de- 
rived from the proximal walls). 

4. Remove the islands of remaining tooth struc- 
ture. On anterior teeth, access is usually un- 
restricted, and the thickest portion of the cut 
ting instrument can be used to maximize 
cutting efficiency (see Fig. 9-2, H). On poste- 
rior teeth, the same pattern is followed as in 
preparing depth grooves for a complete cast 
crown (see Chapter 8). This will include the 
use of a centric cusp bevel, although addi- 
tional occlusal reduction will be needed 
where the porcelain is to be applied (see Fig. 
9-3, A to C . 

Labial (Buccal) Reduction. When completed, 
the reduction of the facial surface should have pro- 
duced sufficient space to accommodate the metal 
substructure and porcelain veneer. A minimum of 1.2 
mm is necessary to permit the ceramist to produce a 
restoration with satisfactory appearance (1.5 mm is 
preferable). This requires significant tooth reduction. 
For comparison, the cervical diameter of a maxillary 
central incisor averages between 6 and 7 mm. 

In the cervical area of small teeth, obtaining opti- 
mal reduction is not always feasible (see Fig. 7-4.) 
Often a compromise is made with lesser reduction 
in the area where the cervical shoulder margin is 
prepared. 

5. Remove the remaining tooth structure be- 
tween depth grooves (see Fig. 9-2,1 to L), cre- 
ating a shoulder at the cervical margin (Fig. 
9-7). If a restoration with a narrow subgingi- 
val metal collar is to be fabricated and suffi- 
cient sulcular depth is present, place the 
shoulder approximately 0.5 mm apical to the 
crest of the free gingiva at this time. Addi- 
tional finishing will then result in a margin 
that is 0.75 to 1 mm subgingival. Use ade- 
quate water spray during the entire phase of 




Fig. 9-7. A, The cervical shoulder is established as the 
tooth structure between the depth grooves is removed. The 
rotary instrument is moved parallel to the intended path of 
withdrawal during this procedure. B, The facial reduction 
should be completed in two phases, initially maintaining 
one half intact for assessment of the adequacy of reduction. 
Note the two distinct planes of reduction on the facial. The 
proximal aspect parallels the cervical reduction on the fa- 
cial wall. C, Facial reduction completed. A 6-degree taper 
has been established between the proximal walls. 



preparation, because a significant amount of 
tooth structure is being removed and copious 
irrigation (along with intermittent strokes) 
will expedite the preparation process. Such a 
cautious approach will prevent unnecessary 
trauma to the pulp. The resulting shoulder 




Section 2 Clinical Procedures-Part I 



should be approximately 1 mm wide and 
should extend well into the proximal embra- 
sures when viewed from the incisal (occlusal) 
side (Fig. 9-8). Where access permits, estab- 
lishing this shoulder from the proximal gin- 
gival crest toward the middle of the facial 
wall is preferred. This will minimize place- 
ment of the initial shoulder preparation too 
close to the epithelial attachment. If the mar- 
gin is established from facial to proximal, a 
tendency exists to "bury" the instrument and 
encroach on the epitheUal attachment. A con- 
scious effort to maintain proper margin posi- 
tion relative to the crest of the free gingiva is 
critical (see Fig. 7-49). The location and spe- 
cific configuration of the facial margin de- 
pend on several factors: the type of metal- 
ceramic restoration selected, the cosmetic 
expectations of the patient, and operator 
preference. 
From a periodontal point of view, a supragingival 
margin is always preferred. Its application is re- 
stricted, however, because patients often object to a 
visible metal collar or discolored root surface. Such 
objections are common, even when the gingival 
margin is not visible during normal function, as in 
patients with a low lip line. This generally limits the 



To ensure esthetics, 
the shoulder margin 
must extend into the 
inlcrproximalarea. 




Fig. 9-8. A, The facial shoulder preparation should wrap 
around into the interproximal embrasure and extend at 
least 1 mm lingual to the proximal contact. B, The shoulder 
preparation extends adequately to the lingual side of the 
proximal contact. Note that on the mesial (visible) side, the 
preparation extends slightly farther than on the distal (cos- 
metically less critical) side. 



use of supragingival margins to posterior teeth (Fig. 
9-9) and to un-discolored anterior teeth (in which 
case a porcelain labial margin is preferred; see Chap- 
ter 24). The optimum location of the margin should 
be carefully determined with the full cooperation of 
the patient. Where a subgingival margin is to be 
placed, careful tissue manipulation is essential; oth- 
erwise, there will be damage that leads to permanent 
gingival recession and subsequent exposure of 
the metal collar. This is most effectively avoided 
through meticulous gingival displacement with a 
cord before finishing (Fig. 9-10). The configuration of 
the margin is also finalized at this time (Fig. 9-11). 

Axial Reduction of the Proximal and Lingual 
Surfaces, (see Fig. 9-2, M to P). Sufficient tooth 
structure must be removed to provide a distinct, 
smooth chamfer of about 0.5 mm width. 

6. Reduce the proximoaxial and linguoaxial sur- 
faces with the diamond held parallel to the in- 
tended path of withdrawal of the restoration. 
These walls should converge slightly from 
cervical to incisal or occlusal. A taper of ap- 
proximately 6 degrees is recommended. On 
anterior teeth, a lingual concavity is prepared 
for adequate clearance for the restorative ma- 
terials). Typically,! mm is required if the 
centric contacts in the completed restoration 
are to be located on metal. When contact is on 
porcelain, additional reduction will be neces- 
sary. For anterior teeth, usually only one 
groove is placed, in the center of the lingual 
surface. For molars, three grooves can be 
placed in a manner similar to that described 
for the all-metal complete cast crown. 




Fig. 9-9. Supragingival margins on the maxillary premo- 
lars. They were possible because of a favorable lip line hid- 
ing the cervical aspect of these posterior teeth. The subgin- 
gival margins on the mandibular premolars were prepared 
only because of previously existing restorations. 



Chapter 9 The Metal-Ceramic Crown Preparation 



I 



7. Make a Ungual alignment groove by posi- 
tioning the diamond parallel to the cervical 
plane of the facial reduction. When the 
round-tipped diamond of appropriate size 
and shape is aligned properly, it will be al- 
most halfway submerged into tooth struc- 
ture. Verify the alignment of the groove, and 
carry the axial reduction from the groove 
along the lingual surface into the proximal; 
maintain the originally selected alignment of 
the diamond at all times. 



As the lingual chamfer is developed, extend 
it buccally into the proximal to blend with the 
interproximal shoulder placed earlier (Fig. 
9-12). Alternatively, a facial approach may be 
used. Although this is slightly more difficult 
initially, after some practice it should be easy 
to eliminate the lingual guiding groove and 
to perform the proximal and lingual axial re- 
duction in one step; however, this requires 
that the diamond be held freehand parallel to 
the path of withdrawal. The proximal flange 




Fig. 9-1 0. A, A gingival displacement cord (under tension) is placed in the interproximal sulcus. B, A 
second instrument can be used to prevent it from rebounding from the sulcus after it has been packed. 



A 




Fig. 9-1 1 . A, After tissue displacement, the facial margin is extended apically. Caution is needed, be- 
cause if the diamond inadvertently grabs the cord, it may be ripped out of the sulcus and traumatize the 
epithelial attachment. B, Note the additional apical extension of the shoulder on the distal aspect. C, The 
entire facial shoulder is placed at a level that will be subgingival after the tissue rebounds. D, The facial 
margin has been prepared to the level of the previously placed cord. 



I 



Section 2 Clinical Procedures-Part I 




Fig. 9-1 2. A lingual chamfer is prepared to allow ade- 
quate space for metal. A smooth transition from interproxi- 
mal shoulder to chamfer is essential. 



that resulted from the shoulder preparation 
can be used as a reference for judging align- 
ment of the rotary instrument (Fig. 9-13). The 
interproximal margin should not be inadver- 
tently placed too far gingivally and thereby 
infringe on the attachment apparatus. It must 
follow the soft tissue contour (see p. 150). On 
posterior teeth, the lingual wall reduction 
blends into the functional cusp bevel placed 
during the occlusal reduction. Anterior teeth 
require an additional step: After preparation 
of the cingulum wall, one or more depth 
grooves are placed in the lingual surface. 
These are approximately 1 mm deep. 

9. Use a football- shaped diamond to reduce 
the lingual surface of anterior teeth (see Fig. 
9-2, P). It is helpful to stop when half this re 
duction has been completed to evaluate 
clearance in the intercuspal position and all 
excursions. The remaining intact tooth struc- 
ture can serve as a reference. 

Finishing. The margin must provide distinct 
resistance to vertical displacement of an explorer 
tip, and it must be smooth and continuous circum- 
ferentially. (A properly finished margin should feel 
like smooth glass slab.) All other line angles should 
be rounded, and the completed preparation should 
have a satin finish free from obvious diamond 
scratch marks. Tissue displacement is particularly 
helpful when finishing subgingival margins (Fig. 
9-14). Sometimes this step is postponed until just 
before impression making after tissue displacement. 

10. Finish the margins with diamonds, hand in- 
struments, or carbides (see Fig. 9-2, Q and 
R). All internal line angles should be ra- 
diused to facilitate the impression-making 
and die-pouring steps (see Fig. 9-2, S). The 




Fig. 9-1 3. A, Proximal reduction of the flange with a fa- 
cial approach. B, Once sufficient tooth structure has been 
removed, the cervical chamfer is prepared simultaneously 
with the lingual axial surface. After the distolingual prepa- 
ration has been completed, the mesial chamfer is blended 
into a smooth transition with the shoulder. 




Fig. 9-14. Controlled tissue displacement can be helpful 
when finishing the margin with a fine-grit diamond or an- 
other rotary instrument. 



finishing steps for the facial margin depend 
on the design of margin chosen (see Table 
7-2 and Fig. 9-15). A porcelain labial margin 
requires proper support for the porcelain. A 
shoulder with a 90-degree cavosurface angle 
is recommended. This type of shoulder can 
also be used for a crown with a conventional 
metal collar and offers the advantage of al- 
lowing the collar to be kept narrow. How- 
ever, there is then the risk of leaving unsup- 
ported enamel. For this reason, the margin 
is often beveled or sloped to create a more 
obtuse cavosurface angle (Fig. 9-16). A 



Chapter 9 The Metal -Cera mi c Crown Preparation 



I 




Fig. 9-1 5. A, Completed preparation. Note that the tran- 
sition from incisal to axial walls is rounded, and a distinct 
90-degree or slightly sloping shoulder has been estabhshed. 
B, Even chamfer width and a smooth transition between 
lingual and axial surfaces. The chamfer is distinct and 
blends smoothly into the facial shoulder. 



1^ 



Fig. 9-16. A, 90-degree shoulder. B, 120-degree shoul- 
der. C, Shoulder bevel. 

flat-ended diamond in a low- speed hand- 
piece creates the 90-degree shoulder. Any 
unsupported enamel must be removed sub- 
sequently by careful planing with a sharp 
chisel. Care must also be taken to orient the 
rotary instrument as it moves around the 
tooth if inadvertent undercuts are to be 
avoided. When a metal-collar design of ce- 
ramic restoration is planned, the need for a 
90-degree shoulder is less critical. A sloping 
shoulder has been advocated to ensure the 
elimination of unsupported enamel and to 
minimize marginal gap width (see Chapter 
7). Such a shoulder (cavosurface angle of 
about 120 degrees) can be accomplished 
with a flat-ended diamond by changing its 
alignment, paying particular attention to the 
configuration of the tooth structure cervical 
to the margin. Alternatively, a hatchet can be 
used to plane the margin to the correct an- 
gulation. Again, be careful to avoid under- 
cutting the axial wall of the preparation 
where it meets the shoulder during finish- 
ing. A shoulder-bevel margin is most effec- 
tively achieved with a flame- shaped carbide 



V^: 




Fig. 9-1 7. The shoulder bevel. 




Fig. 9-1 8. A, Facial and B, lingual views of metal- 
ceramic preparations. 



bur or hand instrument, depending on the 
length of bevel required (Fig. 9-17). Gener- 
ally a short bevel with a cavosurface angle 
of 135 degrees is advocated, although longer 
bevels have been recommended for im- 
proved marginal fit. Special care must be ex- 
erted where the bevel meets the interproxi- 
mal chamfer. The chamfer and bevel should 
be continuous with each other. Care must be 
taken not to damage the epithelial attach- 
ment during beveling; tissue displacement 
before preparation of subgingival bevels is 
recommended. 
11. After a satisfactory facial margin has been 
obtained, round all sharp line angles within 
the preparation (see Fig. 9-2, S). This will fa 
cilitate surface wetting and expedite subse- 
quent procedures (impression making, 
pouring of casts, waxing, and investing). A 
fine-grit diamond operating at low speed is 



I 



Section 2 Clinical Procedures-Part I 

particularly useful. However, where access 
allows, a slightly larger tapered diamond 
may be preferred because the greater diam- 
eter of its tip prevents "ditching" of the 
chamfer. Blend all surfaces together, and re- 




Flg. 9-19. The "wingless" variation does not exhibit the 
defined transition from chamfer to shoulder seen in Fig. 
9-15. Rather, the shoulder gradually narrows toward the 
lingual side. Interproximally, the same criteria for mini- 
mum extension of the shoulder apply as for the wing-type 
or flange preparation. 



move any sharp transitions (see Figs. 9-2, T; 
9-18; and 9-19). 

Evaluation. Areas often missed during finish- 
ing are the incisal edges of anterior preparations 
and the transition from occlusal to axial wall of pos- 
terior preparations. The completed chamfer should 
provide 0.5 mm of space for the restoration at the 
margin. The chamfer must be smooth and continu- 
ous, and when evaluated, a distinct resistance to 
vertical displacement of the tip of an explorer or pe- 
riodontal probe should be felt. The chamfer should 
be continuous with the interproximal shoulder or 
beveled shoulder. The cavosurface angle of the 
chamfer should be slightly obtuse or 90 degrees. 
Under no circumstances should any unsupported 
tooth structure remain, especially at the facial mar- 
gin. Care is also needed to avoid creating an under- 
cut between the facial and lingual walls. This aspect 
of the preparation should be thoroughly evaluated. 
Excessive convergence should also be avoided, be- 
cause this may lead to pulpal exposure. All residual 
debris is removed with thorough irrigation. (Vari- 
ous examples of metal-ceramic preparations are 
shown in Figs. 9-20 and 9-21.) 





r\^'^ 




Fig. 9-20. Metal-ceramic crowns used to restore maxillary incisor teeth. 



Chapter 9 The. Mcta1-Ccramic Crown Pre.paration 





Fig. 9-2 1 . A, Metal-ceramic preparations on the maxillary premolars in conjunction with more con- 
servative preparations on the molars. B, Buccal view of the preparations. Note that, by comparison, con- 
siderable tooth reduction was needed on the premolars to accommodate metal-ceramic restorations. 
C, Except for the molars, all remaining teeth in this patient have been prepared for metal-ceramic 
restorations. Note the subtle variations and modifications of the same underlying theme: wing-type 
preparations on the anterior teeth, wingless on the premolars. D, Mandibular arch of the same patient. 
Many of the smaller mandibular teeth were prepared with wingless restorations. Because of previously 
existing restorations, excessively heavy shoulderlike chamfers resulted on some of the posterior teeth. 



Sifidy Qcie^fiopi^ 



1. Whai are the indications and contraindications for metal-ceramic crowns? 

2. What are the advantages and disadvantages of metoi-ceramic crowns? 

3. What is the recommended armamentarium, and in what sequence should a maxillary centra! incisor be 
prepared, for a metal-ceramic crown? 

4. What are the minimal criteria for each step described above. Why? 

5. What are the differences between wing-type and wingless preparations? When would one be used over 
the other? Why? 

6* Discuss how to determine the byccolingual position of a proximal groove to precisely obtain the desired 
position of the facia! finish line. 




Section 2 Clinical Procedures-Part I 



ISUMMARY 


CHART 








ibidications 


Contraitidications 


Advantages 




Disadvantages 


Estfierics 


Large pulp chamber 


Superior estfieMcs as 


compored 


Removal of substantial tootfi 


If all-ceramic crown i$ 


Intact buccoj woll 


io complete cast 


crown 


structure 


contraindica^ed 


Wheri more conservolive 






Subject to fracture becouse 


Gingiva! involvemen^ 


retainer is technicaily 
Feasible 






porcelain is brittle 

Difficult to obtain accurate 
occlusion in glazed 
porcelain 

Sfiade selection can be 
difficult 

Infer tor estfietics compared 
to ali'ceramic crown 

Expensive 



ChaptfT 9 The Metal-CeTamic Crown Preparation 



■ 



Metal-Ceramic Crown 


Preparation Steps 


Recommended Armamentarium 


Criteria 


Incisal (occlusal) re<iuction 
guide grooves 


Tapered, round-tipped diamond 


1 .5 to 2 mm of cJearance in intercuspal positions 
and all e><cursions 


Incisal (occlusal) reduction 


Tapered, round-tipped diamond 




Labial reduction guide 
grooves {two plane) 


Taperedj round-tipped diamond 


1 .2 to L5 mm of reduction for metal and porce- 
lain (see Fig. 9-1) 


Labial reduction (two plane) 


Tapered, flot^ipped diamond 




Axiol reduction 


Tapered, round -tipped diamond 


6 degrees of convergence 


Lingual reduction 
Finishing of shoulder (or 


Fgotboll-shaped diamond 


should provide 1 mm of clearance in all excur- 
sions and iP (^1 ,5 mm if occlusal is porcelain) 


beveled shoulder) 


Tapered, flat-tipped diamond 
Hand instrument 


Shoulder must extend at least 1 mm lingual to 
proximal contact area; bevel, if selected, 
should be as far incisal as possible relative to 
epithelial attachment 


Finishing 


Tapered, round-tipped diamond 

or cartide 


All line angles rounded and preparation surfaces 
smooth 



The Partial Veneer Crown, 
Inlay, and Onlay Preparations 



An extracoronal metal restoration that covers only 
part of the clinical crown is considered to be a par- 
tial veneer crown. It can also be referred to as a 
partial-coverage restoration. An intracoronal cast 
metal restoration is called an inlay or an onlay if one 
or more cusps are restored. Examples of these 
restorations are presented in Figure 10-1. Partial ve- 
neer crowns generally include all tooth surfaces ex- 
cept the buccal or labial wall in the preparation. 
Whenever feasible, a partial-coverage restoration 
should be selected rather than a complete veneer be- 
cause it preserves more of the tooth's coronal surface. 
However, the preparation is more demanding and is 
not routinely provided by practitioners. Buccolingual 
displacement of the restoration is prevented by inter- 
nal features (e.g., proximal boxes and grooves). The 
partial veneer can be used as a single-tooth restora- 
tion, or it may serve as a retainer for a fixed partial 



A 




Fig. 10-1 A, Partial veneer crowns serving as retainers 
on the premolars for a four-unit FPD replacing the maxil- 
lary first molar. B, Maxillary premolars restored with gold 
inlays, molar restored with gold onlay. These restorations 
have served for about 30 years. 



denture (FPD). It can be used on both anterior and 
posterior teeth. Because it does not cover the entire 
coronal surface, it tends to be less retentive than a 
complete crown and is less resistant to displacement. 
Unless the partial veneer is very carefully prepared, 
the reduced retention may contraindicate its use. In- 
lays and onlays are even less retentive than partial 
veneer crowns and are not recommended for FPD 
abutment retainers. However, they provide the ad- 
vantages of a casting, with less enamel removal than 
a crown. When carefully performed, they can pro- 
duce an exceptionally long-lasting restoration. 

PARTIAL VENEER CROWNS 

Several types of partial veneers exist: for posterior 
teeth-three-quarter, modified three-quarter, and 
seven-eighths crowns; for anterior teeth- three- 
quarter crowns and pinledges. 

The indications, contraindications, advantages, 
and disadvantages of partial veneer crowns will be 
considered first, and any specific deviations that 
pertain to a given preparation will be identified as 
that type is discussed. 

INDICATIONS 

Partial veneer crowns often can be used to restore 
posterior teeth that have lost moderate amounts 
of tooth structure, provided the buccal wall is intact 
and well supported by sound tooth structure. They 
are also commonly used as retainers for a fixed 
partial denture or where restoration or alteration of 
the occlusal surface is needed. Anterior partial ve- 
neers are rarely suitable for restoring damaged 
teeth, but they can be used as retainers, to reestab- 
lish anterior guidance, and to splint teeth. They are 
particularly suitable for teeth with sufficient bulk 
because they can accommodate the necessary reten- 
tive features. 

CONTRAINDICATIONS 

Partial veneer restorations are contraindicated 

on teeth that have a short clinical crown because 



230 



Chapter 10 The Partial Veneer Crown, Inlay, and Onlay Preparations 



I 



retention may not be adequate. They are also 
contraindicated as retainers for long- span FPDs. 
They are rarely suitable for endodontically treated 
teeth, especially anteriors, because insufficient sup- 
porting tooth structure remains for the retentive fea- 
tures. Likewise, they should not be used on en- 
dodontically treated posterior teeth if the buccal 
cusps are weakened by the access cavity or on teeth 
with an extensively damaged crown. As is true of all 
cast restorations, partial veneers are contraindicated 
in dentitions with active caries or periodontal 
disease. 

The shape and alignment of teeth are important 
determinants of the feasibility of partial veneer 
crowns. The alignment of axial surfaces should be 
evaluated, and partial veneers should not be placed 
on teeth that are proximally bulbous. Making the 
necessary proximal grooves on these teeth is likely 
to leave unsupported enamel. Similarly it may be 
impossible to prepare adequate grooves on thin 
teeth of restricted faciolingual dimension. 

Partial veneers are usually prepared parallel to the 
long axis of the tooth, and poorly aligned abutment 
teeth may not be suitable. When poorly aligned teeth 
are being prepared for a partial-coverage restoration, 
problems with unsupported enamel often result. 

ADVANTAGES 

The primary advantage associated with partial ve- 
neer crowns is conservation of tooth structure. An- 
other advantage is reduced pulpal and periodontal 
insult during tooth preparation. Access to supra- 
gingival margins is rather easy and allows the oper- 
ator to perform selected finishing procedures that 
are more difficult or impossible with complete- 
coverage restorations. Access is also better for oral 
hygiene. Because less of the margin approximates 
the soft tissues subgingivally, there is less gingival 
involvement than with complete coverage. 

During cementation of a partial veneer, the luting 
agent can escape more easily, which produces rela- 
tively good seating of the restoration. Because of di- 
rect visibility, verification of seating and cement re- 
moval are simple. After cementation, the remaining 
intact facial or buccal tooth structure permits elec- 
tric vitality testing. 

DISADVANTAGES 

Partial veneer restorations have less retention and 
resistance than complete cast crowns. Preparing the 
tooth for this type of coverage is difficult, primarily 
because only limited adjustments can be made in 
the path of withdrawal. The placement of grooves, 
boxes, and pinholes requires dexterity from the op- 
erator. Some metal is displayed in the completed 



restoration, which may be unacceptable to patients 
with high cosmetic expectations. 

PREPARATION 

The following discussions will cover the teeth most 
commonly prepared for partial veneer restorations. 
It should be noted that the use of partial veneers on 
anterior teeth has declined because of the difficulty 
in achieving an esthetic result. The technique illus- 
trated may be suitable for posterior teeth and, with 
minimal variation, for other teeth. On both poste- 
rior and anterior teeth, meticulous care and preci- 
sion are required if partial veneers are to be a 
successful (conservative) alternative to complete- 
coverage restorations. 

Armamentarium (Fig. 10-2). The necessary in- 
struments for a partial veneer crown preparation in- 
clude the following: 

• Narrow (approximately 0.8 mm), round-tipped, 
tapered diamond (regular or coarse grit) 

• Regular-size, (approximately 1.2 mm), round- 
tipped, tapered diamond (fine grit) or carbide 

• Football- shaped or wheel- shaped diamond 
(regular grit) 

• Tapered and straight carbide fissure burs 

• Small, round carbide bur 

• Small-diameter twist drill 

• Inverted-cone carbide bur 

• Finishing stones 

• Mirror 

• Explorer and periodontal probe 

• Chisels 

This is the typical armamentarium for a partial 
veneer crown preparation. Depending on operator 
preference, additional instruments can be used. The 
regular- or coarse-grit diamonds are used for bulk 
reduction, and the fine-grit diamonds or carbides 
are used for finishing. Pinholes are prepared with 
the twist drill and finalized with a tapered carbide. 
The fissure burs are recommended for preparing 




Fig. 10-2. Armamentarium for a partial veneer crown 
preparation. 



I 



Section 2 Clinical Procedures-Part I 



boxes and ledges, and the inverted-cone carbide is 
recommended for preparing incisal offsets. Hand 
instruments can be used to finish proximal flares 
and bevels. A periodontal probe is invaluable when 
assessing the direction and dimension of the vari- 
ous steps. 

POSTERIOR PARTIAL VENEER CROWN PREPARATIONS 

Maxillary Premolar Three-quarter Crown (Fig. 

10-3). The three-quarter crown preparation derives 
its name from the number of axial walls involved. 



Except for a slight bevel or chamfer placed along the 
buccocclusal line angle, the buccal tooth surface re- 
mains intact. The other surfaces (including the oc- 
clusal surface) are prepared to accommodate a cast- 
ing in the same manner as a complete crown 
preparation (see Chapter 8), differing only in the 
need for axial retention grooves. 

Occlusal Reduction. Upon the completion of 
occlusal reduction, a clearance of at least 1.5 mm 
should exist on the centric cusp and at least 1.0 mm 




E f G 

Fig. 10-3. The maxillary premolar three-quarter crown. A, Initial depth holes are placed in the mesial 
and distal fossae approximately 0.8 mm deep. B, They are connected by a guiding groove that extends 
through the central groove. Additional guiding grooves are placed on the lingual cusp similar to those 
for a complete cast crown (see Fig. 8-8). The depth cut placed on the triangular ridge of the buccal cusp 
becomes shallower as it approaches the cusp tip. C, Half the occlusal reduction is completed. Note the 
centric cusp bevel. The occlusocervical height of the buccal surface is not reduced at this stage. D, Oc- 
clusal reduction completed. E, After guiding grooves are placed in the lingual surface of the tooth paral- 
lel to the proposed path of withdrawal, the proximoaxial and linguoaxial reductions are initiated. Simul- 
taneously a smooth and even- width cervical chamfer is created. F, When the axial reduction of the first 
half is considered acceptable, the other half can begin. G, Proximal grooves are placed perpendicular to 
the prepared surface, and the buccal wall of each groove is flared to leave no unsupported enamel. The 
proximal flares are connected with a narrow contrabevel. After rounding of the line angles, the prepara- 
tion is complete. H, The interproximal clearance relative to adjacent teeth extends cervically as well as 
near the occlusal aspect of the buccal flares of the proximal grooves. 



Chapter 10 The Partial Veneer Crown, Inlay, and Onlay Preparations 



I 



on the noncentric cusp and in the central groove. Si- 
multaneously, the tooth should be prepared so that 
the restoration displays a minimum of metal, with 
preservation of the buccal wall outline. 

1. Before any partial veneer crown preparation, 
mark the proposed location of the margin of 
the completed preparation on the tooth with 
a pencil (Fig. 10-4). 

2. Place depth grooves for the occlusal reduc- 
tion. These should be made with a tapered 
carbide or narrow diamond in the develop 
mental grooves of the mesial and distal fos- 
sae and on the crest of the triangular ridge. 
In the central groove they should be slightly 
less (about 0.2 mm) than 1 mm deep to 
allow for finishing; on the centric (lingual) 
cusp they should be slightly less than 
1.5 mm deep in the location of the occlusal 
contacts. 

3. Place three depth grooves on the lingual in- 
cline of the buccal cusp. Initially, these should 
be kept somewhat shallow as they approach 
the buccal cusp ridge (Fig. 10-3, B). In the area 
of occlusal contact, the groove should be 
about 0.8 mm deep so that there will be at 
least 1 mm of clearance after finishing. 

4. Verify groove depth with a periodontal 
probe. When this is found to be acceptable, 
remove the islands of tooth structure remain- 
ing between the grooves (Fig. 10-3, C and D). 

5. Assess the amount of occlusal clearance in 
the intercuspal position and in all excursive 
movements of the mandible (Fig. 10-5). 
Grinding a small concavity on the incline of 
the buccal cusp may help obtain sufficient 
clearance while maintaining the original oc- 
clusocervical dimension of the buccal tooth 
surface (Fig. 10-6). 




Axial Reduction 



6. 



7. 



Place grooves for axial alignment in the cen- 
ter of the lingual surface and in the mesiolin- 
gual and distolingual transitional line angles. 
These should be parallel to the long axis of 
the tooth and should not exceed half the 
width of the tip of the diamond used to place 
them. 

Because the path of withdrawal of a partial 
veneer is critical, assess these grooves care- 
fully when correction is still possible. A com 
mon error is to incline the path of withdrawal 
toward the buccal. This either reduces reten- 
tion or leads to an excessive display of metal. 
A periodontal probe placed in each groove 
should be carefully viewed in both planes 
(mesiodistal and buccolingual). It often helps 
to pour an irreversible hydrocolloid (algi- 
nate) impression in fast- setting plaster and to 
evaluate the cast with a dental surveyor, par- 
ticularly if multiple partial veneers are being 
used as retainers for an FPD. 




Fig. 1 0-5. A common error is insufficient reduction of 
tooth structure in the marginal ridge area (arrow). 



Light :i 




1 ,5 mm 



Fig. 10-4. The anticipated location of the completed 
preparation is marked with a pencil. 



Fig. 1 0-6. Recommended minimum clearances for re- 
duction of a partial veneer crown preparation. SUght hol- 
low grinding of the lingual incUne of the buccal cusp re- 
sults in an acceptable clearance with the least display of 
metal. Also, the final restoration retains the normal con- 
tours of the cuspal ridge, so incident Hght is not reflected, 
and the restoration is less evident. 



I 



9. 



Section 2 Clinical Procedures-Part I 

After verifying the alignment, remove tooth 
structure between the guide grooves (with a 
smooth continuous motion) and place a cer- 
vical chamfer (Fig. 10-7). 
Carry the diamond into the proximal em- 
brasure and reduce the proximal wall (Fig. 
10-3, E and F). For proper reduction of the 
axial tooth surface, it is important to under- 
stand the factors that determine correct po- 
sitioning of the proximal groove. A proximal 
groove is placed parallel to the path of with- 
drawal. Normally, unsupported tooth struc- 
ture will remain on the buccal side of the 
groove, and this side is flared to remove it. 
Figure 10-8 illustrates the relationship 
among the initial axial reduction, groove 
placement, and location of the cavosurface 
angle where the flare meets the intact buccal 
wall. The cavosurface angle is especially sig- 
nificant when preparing a tooth for a partial 
veneer that should display a minimum of 
metal; the further to the buccal the margin 
is, the more gold will be visible. A subtle but 




Fig. 1 0-7. Proximal and lingual axial reduction is per- 
formed with a round-tipped diamond. The proximal reduc- 
tion is stopped short of the proposed location of the buccal 
margin. 



extremely important variable that deter- 
mines the final location of the cavosurface 
angle is the apical extension of the prepara- 
tion. As the cervical chamfer extends closer 
to the cementoenamel junction, more axial 
tooth structure is removed. Consequently, 
the deepest portion of the groove (its pulpal 
wall) will be located slightly closer to the 
center of the tooth. This results in a flare that 
can extend farther onto the facial or buccal 
surface than desirable. Marking the location 
of the intended facial flare on the tooth with 
a pencil before initiating the proximoaxial 
reduction is helpful. The intersection of this 
mark with the reduced occlusal surface is a 
convenient reference point. 

10. Stop the proximal reduction well short of 
the pencil mark and usually slightly short of 
breaking the proximal contact (Fig. 10-9). 
The resulting flange should be parallel to 
the linguoaxial preparation, with the cham- 
fer placed sufficiently cervical to provide at 
least 0.6 mm of clearance with the adjacent 
tooth and the axial wall allowing for a prox- 
imal groove of at least 4 mm of length oc- 
clusocervically (see Fig. 10-3, F). 

Groove Placement. Preparation of the proxi- 
mal grooves is best done with a tapered carbide bur. 

11. Position the bur against the interproximal 
flange parallel to the path of withdrawal 
and make a groove perpendicular to the ax- 
ial surface. The groove need not be deeper 
than 1 mm at its cervical end but may be 
deeper near its occlusal end (Fig. 10-10). 
During this stage, the bur must be held pre- 
cisely parallel to the selected path of with- 
drawal. Allowing it to tip axially will result 
in excessive taper between opposing proxi- 
mal grooves, which is a common error. The 





Fig. 1 0-8. A, Upon completion of the proximal axial re- 
duction, a groove is placed perpendicular to the prepared 
surface. B, Note that some unsupported tooth structure re- 
mains at the cavosurface angle. C, After the buccal wall of 
the proximal groove is flared, no unsupported tooth struc- 
ture remains. NOTE: It is important to anticipate in ad 
vance the influence of the buccal extent of the proximoaxial 
reduction (A) on the ultimate location of the margin. 




Fig. 1 0-9. The distal proximal reduction is stopped be- 
fore breaking proximal contact. After groove placement and 
subsequent flaring, interproximal clearance will result. 



Chapter 10 The Partial Veneer Crown, Tnlay, and Onlay Preparations 



I 



criteria that need to be met consist of the fol- 
lowing (see Figs. 10-9 and 10-11): 
The grooves should resist lingual displacement 

of a periodontal probe or explorer. 
The walls of the grooves should not be undercut 

relative to the selected path of withdrawal. 
The walls should be flared toward the intact buc- 
cal surface of the tooth (see Fig. 10-3, G and H). 





Fig. 1 0-1 0. Because of the rotary instrument's taper 
(A), the proximal groove is deeper near the occlusal table. 
The floor of the groove should be flat and smooth. Often 
the proximal chamfer will extend slightly cervically to the 
floor of the groove. If only minimal difference exists, as in 
B, the cervical margin adjacent to the groove can be 
beveled. The recommended occlusocervical height for a 
proximal groove is 4 mm. 




Fig. 10-1 1 . The 90-degree angle between the lingual 
walls of the proximal grooves will resist lingual displace- 
ment. Because the buccal aspect of the grooves has been ad- 
equately flared, no unsupported tooth structure remains. 



Depending on available access, it may be feasible 
to complete the flaring with the same rotary instru- 
ment that was used to place the groove (Fig. 10-12). 
However, removing the last lip of unsupported 
tooth structure with a chisel is often a better option, 
because this minimizes the risk of damage to the ad- 
jacent tooth. 

Buccocclusal Contrahevel 

12. Connect the mesial and distal flares with a 
narrow contrabevel that follows the buccal 
cusp ridges. This can be placed with a dia 
mond, a carbide, or even a hand instrument. 
Its primary purpose is to remove any un- 
supported enamel and thereby protect the 
buccal cusp tip from chipping during func- 
tion. If group function is planned (as op- 
posed to a mutually protected occlusion), a 
heavier bevel, chamfer, or occlusal offset 
will be needed, because tooth contact occurs 
in this area during excursive movement. 
The bevel should remain within the curva- 
ture of the cusp tip rather than extend onto 
the buccal wall (Fig. 10-13). This will result 
in a convex shape of the restoration, and 
light will be prevented from reflecting back 
to a casual observer (see Fig. 10-6). Thus the 
restoration will be less obvious, and the out- 
line form of remaining buccal enamel will 
be perceived as the shape of the tooth. 

Occlusal Offset. If additional bulk is needed to 
ensure rigidity of the restoration, it can be provided 
with an occlusal offset. This V-shaped groove ex- 
tends from the proximal grooves along the buccal 
cusp. It is not usually necessary for posterior partial 
veneer crowns but is essential for the structural 
durability of anterior partial veneer crowns. This is 
described in detail on p. 243. 



B 




Fig. 10-12. A, Initial preparation of the mesial proximal groove. Note that the carbide is oriented 
parallel to the path of withdrawal as dictated by the lingual surface of the tooth. B, Initial flaring has re- 
sulted in ehmination of most unsupported tooth structure. C, Hand or rotary instruments will be used to 
refine these proximal flares and remove all unsupported enamel. 



I 



Section 2 Clinical Procedures-Part I 




Fig. 1 0-1 3. The buccocclusal contrabevel remains 
within the curvature of the cusp tip rather than extending 
onto the buccal surface. 




Fig. 1 0-14. A fine-grit diamond in a low-speed con- 
traangle is used to place the buccocclusal contrabevel con- 
necting the mesioproximal and distoproximal flares. 



Finishing 

13. Round all sharp internal line angles to facil- 
itate subsequent procedures. A fine-grit dia- 
mond or carbide can be used to blend the 
surfaces (Fig. 10-14). 

14. Reevaluate the flares, paying particular at- 
tention to any remaining undercuts, which 
must be removed. The flares should be 
straight and smooth, with sufficient clear- 




Fig. 10-15. Three-quarter crown preparation on a maxil- 
lary molar. Note that the occlusal reduction follows normal 
anatomic form. 




Fig. 1 0-1 6. The three-quarter crown preparation on a 
maxillary first molar. 



ance between them and the adjacent tooth. 
A minimum clearance of 0.6 mm is recom- 
mended. The mesial flare cannot extend be- 
yond the transitional line angle. However, 
because the distal margin is less visible, it 
may extend slightly farther to the buccal, al- 
lowing better access for oral hygiene. 

Maxillary Molar Three-quarter Crown (Fig. 

10-15 and Fig. 10-16). The principles used in a pre- 
molar preparation also apply for a maxillary molar. 
However, some additional leeway may exist for 
groove placement because more tooth structure is 
present on molars than on premolars. Also, because 
of their less prominent position in the dental arch, 
molars are less visible. As a result, the mesioproxi- 
mal flare can sometimes be extended onto the buc- 
cal surface without incurring esthetic liability. 

Maxillary Molar Seven-eighths Crown (Fig. 

10-17). The seven-eighths crown preparation in- 
cludes, in addition to the surfaces covered by the 
three-quarter crown, the distal half of the buccal 
surface. Therefore the mesial aspect of this prepara- 
tion resembles that for a three-quarter crown; the 



Chapter 10 The Partial Veneer Crown, Inlay, and Onlay Preparations 



I 




Fig. 10-17. The maxillary molar seven-eighths crown preparation. A, Occlusal depth grooves. On the 
lingual of the mesiobuccal cusp, they are identical to grooves for any centric cusp. On the buccal, note 
their difference from grooves placed on the triangular ridges. The mesial groove becomes shallower as it 
approaches the cuspal ridge; the distal extends through the cuspal ridge. B, Mesial half of the occlusal 
reduction is completed. Normal occlusal form can be recognized in the reduced area. C, Occlusal reduc- 
tion completed. D, Distal half of the axial reduction completed. This is comparable to the preparation for 
a complete cast crown. The rotary instrument is moved parallel to the guiding grooves placed in the Un- 
gual tooth surface. E, Mesial half of the axial reduction completed and a proximal groove placed. F, The 
buccal groove, with flaring of the mesial groove. Note the monoplane of the flare, extending from the 
deepest portion of the groove to the cavosurface angle. G, A contrabevel connects the mesial flare with 
the buccal groove. The mesial wall of the buccal groove is smooth and has a 90-degree cavosurface an- 
gle, leaving no unsupported enamel. 



distal aspect resembles that for a complete crown. 
The mesial half of the buccal tooth surface remains 
intact and is protected by a narrow contrabevel or 
chamfer similar to the one used in the three-quarter 
crown preparation. A distal groove may be placed, 



although generally this is not necessary. A groove in 
the middle of the buccal surface is placed parallel to 
the path of withdrawal. Distal to this groove the 
buccal surface is reduced in two planes, cervical and 
occlusal, with the cervical paralleling the path of 



I 



Section 2 Clinical Procedures-Part I 



withdrawal and the occlusal following the normal 
anatomic contour. The lingual surface of the tooth 
also is reduced in two planes, and centric cusp 
bevels are incorporated. 

Occlusal Reduction. Upon completion of the 
occlusal reduction, adequate clearance should exist 
in all excursive movements of the mandible. Mini- 
mum measurements are the same as for the 
three-quarter crown preparation. 

1. Place depth grooves in the central and devel- 
opmental grooves as well as on the crests of 
the triangular ridges. To delineate the extent of 
the lingual centric cusp bevel, they should ex- 
tend onto the lingual surface of the tooth. On 
the lingual incline of the mesiobuccal cusp 
they will resemble depth cuts for the three- 
quarter crown preparation. On the distobuccal 
cusp they should be approximately 0.8 mm 
deep to provide sufficient occlusal clearance 
for this noncentric cusp (see Fig. 10-17, A). 

2. Remove the tooth structure between the 
depth grooves. Concave shaping of the result- 
ing mesiobuccal incline may again prove use- 
ful because it will permit the occlusocervical 
height of the cusp to be maintained. When 
completed, this bevel should provide 1.5 mm 
of clearance in the intercuspal position as well 
as throughout all excursive movements of the 
mandible (see Fig. 10-17, B and C). 

Axial Reduction, in principle, the steps for ax- 
ial reduction follow those for occlusal reduction. 

3. Place three alignment grooves in the lingual 
wall and transfer the selected path of with- 
drawal to the distobuccal transitional line an- 
gle area, where a fourth alignment groove 
can be placed. 

4. Start the reduction in the middle of the lin- 
gual surface. The mesial half is prepared like 
a three-quarter crown and the distal half like 
a complete crown (see Fig. 10-17, D). 

5. Carry the facial reduction sufficiently mesial 
to include the buccal groove. Although the 
occlusal half of the buccal surface of maxil 
lary molars is rather flat, some additional re- 
duction may be necessary in the occlusal 
third. This follows the normal anatomic con- 
figuration of the tooth and often resembles a 
small version of the centric cusp bevel. If cor- 
rectly performed, the reduction will allow for 
contouring of the restoration so that when 
viewed from the mesial, the distal half of the 
restoration is hidden behind the mesiobuccal 
cusp. A frequent error is to overtaper the 




Fig. 10-18. The seven-eighths crown preparation. Note 
that adequate clearance has been estabUshed. From this 
perspective it is evident why Httle or no flaring is necessary 
for the buccal groove as opposed to the considerable flaring 
needed for the mesial groove. 



buccal wall segment, with resulting loss of 
retention. 

Groove Placement, Flaring, and Contrabevel 

6. Prepare the mesial groove like the three- 
quarter crown (see Fig. 10-17, E and F). 

7. Place the buccal groove parallel to the mesial 
groove and perpendicular to the buccoaxial 
wall. Often it is not necessary to flare the buc 
cal groove because the flat configuration of 
this area of the tooth precludes any unsup- 
ported enamel after the groove is placed. The 
buccal groove should resist mesiodistal dis- 
placement of a probe. 

8. Connect the two grooves with a smooth con- 
trabevel that follows the ridge of the mesiobuc- 
cal cusp (see Fig. 10-17, G). This bevel should 
meet the same criteria as described in the 
three-quarter crown preparation. Adequate 
clearance must be established interproximally 
upon completion (Fig. 10-18). All surfaces are 
finished to the same specifications as the pre- 
ceding preparations (Fig. 10-19). 

Mandibular Premolar Modified Three-quarter 
Crown (Fig. 10-20). Mandibular partial veneer 
preparations are made more often on premolars 
than on molars. They differ from maxillary molar 
three-quarter crown preparations in two respects: 
Additional retention is required because of the 
shorter crown lengths of mandibular teeth. 
This can be obtained by extending the prepa- 
ration buccally, although because of their 
rather prominent position in the dental arch, 
these teeth should be modified only distal to 
their height of contour (Fig. 10-21). 
The axial surface that is not prepared (the buccal) 
includes the functional cusp. This means that 
additional tooth structure must be removed to 
provide sufficient bulk of metal for strength. 



ChaptfT 1 The. Partial Vf.ne.eT Crown. Tn1ay, and On1 ay Preparations 



I 




Fig. 10-19. A, Seven-eighths crowns 
restoring maxillary molars. B and C, Fixed 
partial denture retainers: a seven-eighths 
crown as the distal and a three-quarter 
crown as the mesial. 




Fig. 1 0-20. The mandibular premolar modified three-quarter crown preparation. A, Depth holes 
placed in the mesial and distal fossae approximately 0.8 mm deep. B, The holes are connected by a guid- 
ing groove that extends through the central groove and the mesial and distal marginal ridges. Guiding 
grooves are also placed in the buccal and Ungual triangular ridges, extending through the cuspal ridges 
on both sides. C, Half the occlusal reduction is completed. D, Occlusal reduction and mesial half of the 
axial reduction are completed. E, Axial reduction is completed. The proximal grooves have been placed. 
Note that the distal groove is located close to the buccolingual center of the tooth. This permits retention 
of considerable tooth structure in the area of the distobuccal line angle, enhancing the resistance form of 
the preparation. F, The mesial groove has been flared and the centric cusp chamfer placed. G, Facial 
view. There is considerable width of the chamfer on the centric cusp. Note that the distobuccal cervical 
margin angles occlusally as it progresses mesially. This permits a more conservative tooth preparation in 
the area of the distobuccal modification that is placed to improve resistance form. 



I 



Section 2 Clinical Procedures-Part I 

A i 




Fig. 10-21 . Modified three-quarter crown restoring a mandibular second premolar. It is serving as 
the anterior retainer for a three-unit FPD. Because the distobuccal modification remains in the distal 
fourth of the buccal preparation, it is hidden behind the normal height of contour of the buccal tooth 
surface. Note the considerable thickness of gold that protects the buccal cusp. 



Occlusal Reduction 

1. Place 0.8-mm depth grooves on the buccal in- 
clines of the lingual cusp and 1.3 -mm 
grooves on the lingual inclines of the buccal 
cusp (see Fig. 10-20, A and B). These guiding 
grooves are once again placed to follow the 
basic groove and fissure pattern of the oc- 
clusal surface. Only one depth cut needs to be 
placed to accommodate the functional cusp 
bevel on the distal aspect of the distal ridge. 

2. Reduce the occlusal surface by removing the 
tooth structure between the grooves (see Fig. 
10-20, C). 

Axial Reduction 

3. Place guiding grooves on the lingual surface 
to parallel the proposed path of withdrawal 
and the long axis of the tooth. 

4. Prepare the mesial as already described for 
the three-quarter and seven-eighths crown 
(see Fig. 10-20, D). 

5. Reduce the distal surface as for a complete 
crown, extending the preparation to the tran- 
sitional line angle and onto the buccal sur 
face. However, it should not extend mesially 
beyond the middle of the distal half of the 
buccal surface, and the chamfer should not 
extend too far cervically; otherwise, the dis- 
tobuccal line angle will be unnecessarily re- 
duced, which would decrease the resistance 
form (see Fig. 10-20, E). 

Finishing. The modified three-quarter crown 
preparation can include two or three grooves. 

6. Place the mesial and buccal grooves as 
described for the seven-eighths crown (see 
Fig. 10-20, F). Another distal groove may be 
placed. In general, to gain as much length as 



possible, the grooves of the three-quarter 
crown should be slightly buccal. Care must 
be taken so that the distal groove is slightly 
closer to the center of the distal wall (so the 
distobuccal line angle will not be under- 
mined). 
7. Connect the mesial and buccal grooves with 
a centric cusp chamfer after the grooves and 
mesial flare have been placed and evaluated. 
The chamfer must be heavy enough to allow 
1.5 mm of clearance in the area of occlusal 
contact (see Fig. 10-20, G). A regular or thick 
diamond is used to place the chamfer, which 
should connect the grooves and provide a 
protective "staple" linkage of alloy in the 
completed restoration. Insufficient tooth re- 
duction where this chamfer meets the mesial 
flare is a common error. Finally, all prepared 
surfaces are smoothed and the intemal line 
angles rounded. 

ANTERIOR PARTIAL VENEER CROWN PREPARATIONS 

As Stated, with the advent of metal-ceramic restora- 
tions, the use of partial veneers on anterior teeth has 
become rare. Nevertheless, two anterior partial ve- 
neer crown preparations are worthy of considera- 
tion (Figs. 10-22 and 10-23). 

Maxillary Canine Three-quarter Crown (Figs. 

10-24 and 10-25). The three-quarter crown on a 
maxillary canine is probably one of the most de- 
manding of all tooth preparations. As with such 
preparations on other teeth, on a maxillary canine it 
involves the proximal and lingual surfaces and 
leaves the facial surface intact. However, the greater 
degree of difficulty stems from the different shape of 
the canine tooth. Unless the placement of grooves is 
determined very precisely in advance, there will be 



Chapter 10 The Partial Veneer Crown, Inlay, and Onlay Preparations 



I 




Fig. 1 0-22. A, Deficient anterior guidance resulting from years of parafunctional activity. B, An ante- 
rior partial veneer crown has reestablished it, allowing the intact sound labial tooth structure to be re- 
tained as a conservative alternative to a metal- ceramic restoration. 




Fig. 1 0-23. A, Caries-free canine and lateral incisor of adequate bulk- excellent candidates for ante- 
rior partial veneer crowns. B, The canine restored with a three-quarter crown, serving as the anterior re- 
tainer for a three-unit FPD to replace the first premolar. The lateral incisor has been restored with a mod- 
ified pinledge that serves as a retainer for an anterior four-unit FPD. Satisfactory esthetics (C) with 
minimal display of metal are apparent. 



an undesirable display of metal in the interproximal 
embrasures (see Fig. 10-25, A and B). The relatively 
short proximal walls do not allow much correction 
after initial groove placement. Similarly, the greater 
degree of curvature in each proximal wall immedi- 
ately adjacent to the contact area significantly influ- 
ences the location of the preparation's facial margin. 



Incisal and Lingual Reduction 

1. Remove enough enamel to allow 1 mm of 
metal thickness. The design of the incisal 
bevel should prevent contact between oppos 
ing teeth and the incisal margin. However, 
the original configuration of the facial surface 
should be preserved without significant 




Fig. 1 0-24. The maxillary canine three-quarter crown preparation. A, A guiding groove is placed on 
the lingual surface. B, Half the lingual surface is reduced. Clearance is verified before reduction of the 
other half. C, Lingual reduction is completed, with an incisal bevel placed. No significant change has oc- 
curred in the incisocervical height. D, After an alignment groove is placed in the center of the cingulum 
wall, half the axial reduction is complete. Note that the path of withdrawal parallels the incisal or mid- 
dle third of the labial surface. As a result, the lingual chamfer is quite wide, perhaps even resembling a 
shoulder. This permits paralleling of the cingulum wall, with the proximal grooves and pinhole provid- 
ing additional retention. E, Axial reduction is completed. Any final modification of the path of with- 
drawal is done at this time before groove placement. F, Proximal grooves. The visible mesial groove has 
been flared, but unsupported enamel remains on both grooves where they meet the incisal bevel. 
G, Completed preparation. The Ungual pinhole is surrounded by adequate dentin. Note the horizontal 
ledge prepared before pinhole placement. 




Fig. 1 0-25. a. Proposed margin location outlined on the tooth with a pencil. B, Careful assessment of 
the anticipated outline from as many directions as possible is valuable at this time. C, Preparing the in- 
cisal bevel. Typically a Hngually tilted bevel is prepared at a 45 -degree angle to the long axis of the tooth. 
D, The Ungual surface is reduced with a wheel- or footbaU- shaped diamond. 



Chapter 10 The Partial Veneer Crown, Inlay, and Onlay Preparations 



I 



incisal reduction of the tooth. Outlining the 
anticipated location of the margin with a pen- 
cil can be helpful. 

2. Place depth grooves for both the incisal bevel 
and the lingual reduction (see Fig. 10-24, A). 
The direction of the bevel may vary some 
what depending on the configuration of the 
tooth. Generally it will make an angle of ap- 
proximately 45 degrees with the long axis of 
the tooth. 

3. After the depth has been verified, perform 
the reduction. A football- or wheel-shaped di- 
amond is used to reduce the concave lingual 
wall (see Figs. 10-24, B, and 10-25, D). The lin- 
gual reduction should not extend onto the 
cingulum itself, which will be prepared as 
part of the axial reduction. (The completed 
reduction is shown in Fig. 10-24, C.) 

Axial Reduction and Groove Placement. The 

path of withdrawal of the restoration must be accu- 
rately determined before axial reduction. Mesiodis- 
tally it should parallel the long axis of the tooth; 
buccolingually it should parallel the middle third or 
incisal two thirds of the facial surface. This will per- 
mit the preparation of proximal grooves of opti- 
mum length in an area of the tooth where sufficient 
bulk is present. 

4. To enhance the retention and resistance form 
of the preparation, place a slightly exagger- 
ated chamfer on the Ungual aspect of the tooth 
(see Fig. 10-24, D) and a guiding groove in the 




Fig. 10-26. A, A regular-grit diamond is used to com- 
plete the axial reduction. Mesiodistally the diamond is ori- 
ented parallel to the long axis of the tooth. B, When com- 
pleted, a mesial and distal flange results that will serve as a 
guide during preparation of the proximal groove. 



middle of the lingual wall. When alignment 
has been verified, the axial reduction can be 
performed in the same manner as the other 
preparations (Fig. 10-26). It is important to un- 
derstand the difference between this phase of 
the preparation on a canine, with little bulk of 
lingual tooth structure as opposed to a premo- 
lar or molar. After completion, a proximal 
flange should result that will guide the rotary 
instrument during groove placement (see Figs. 
10-24, E, and 10-26, B). The technical aspects of 
the preparation of proximal grooves are like 
those described for the other partial veneer 
preparations (Figs. 10-27 and 10-28). The pri- 
mary difference is the direction in which the 
groove is prepared. Because the groove is 
placed perpendicular to the proximal wall, its 
deepest portion will be slightly labial to the 
proximal flange that results when proximo ax- 
ial reduction is completed. As a result, the 
proximal flares will extend slightly farther 
onto the facial surface. This is even more ac- 
centuated by the curvature of the proximal 
wall (Fig. 10-29). Meticulous assessment of the 
needed extent of the initial axial reduction is a 
prerequisite for successful preparation (see 
Fig. 10-24, F, and 10-30). (The required inter- 
proximal clearance is illustrated in Fig. 10-31.) 

Incisal Offset and Lingual Pinhole. Anterior 
partial veneer crowns require a means of reinforce- 
ment for preserving the casting's integrity. Posterior 
three-quarter crowns usually do not need as much 
additional reinforcement because the solid "corru- 
gated" occlusal surface provides rigidity. For an an- 
terior tooth, an incisal offset or groove is needed to 
create a band of thicker metal to provide a "staple" 




Axial 
reduction 



Groove 



Flare 



Fig. 10-27. A, Because the groove is prepared perpen- 
dicular to the proximal surface of the tooth, its deepest por- 
tion will be slightly buccal to where axial reduction was 
halted. B, The dotted line indicates the proposed flare. Note 
that the curvature of the tooth causes the final margin to be 
located a considerable distance buccal to where the initial 
axial reduction stopped. C, Completed flares. 




Fig. 1 0-28. A, A tapered carbide is used to place the proximal groove. B, Initial groove preparation is 
completed. C, The carbide is moved parallel to itself. D, Mesial and distal grooves must be prepared in 
strict alignment. 




Fig. 1 0-29. Differences between the proximal flares on premolars and canines. A designates where 
the initial proximal reduction is halted. Because a facial component is present in the direction of groove 
placement on the canine, as opposed to the premolar, the starting point (B) for the flare is located farther 
to the facial. In conjunction with the greater degree of proximal curvature of canines, it is critical that the 
initial axial reduction not be carried too far facially; otherwise, the final margin will extend too far onto 
the labial surface of the tooth and result in excessive display of metal. 




Fig. 1 0-30. A, Unsupported enamel remaining after initial groove placement. B, A carbide bur can be 
used to flare the grooves. C, The flared groove. Note the irregularity of the margin near the cervical as- 
pect of the groove. D, After the flaring. Note that a mesial box, rather than a groove, has been prepared. 
This restoration is designed to contain an intracoronal removable partial denture rest; hence, the box. 
Nevertheless, there is adequate resistance to lingual displacement. E, A special mandrel is placed in the 
box to ensure that it fits within its confines. It is identical in size to the male attachment of the RPD. 



Chapter 10 The Partial Veneer Crown, Tnlay, and Onlay Preparations 



I 




Fig. 1 0-31 . Completed three-quarter crown preparation. 
Note the location of the facial margin relative to the adja- 
cent teeth. Sufficient interproximal clearance has been es- 
tablished, but unnecessary display of metal is avoided. 




Fig. 10-32. An inverted-cone diamond or carbide can be 
used to prepare the incisal offset. Note the faciolingual in- 
clination of the rotary instruments. 



configuration. This provides additional rigidity and 
resistance against bending of the casting. 

5. Connect the mesial and distal grooves with 
an incisal offset. It should improve the gen- 
eral resistance form of the preparation 
against lingual displacement and should 
have a V configuration. Sufficient dentin 
must be preserved facially to the offset to pre- 
vent the metal from being visible through the 
translucent tooth enamel. This is most effec- 
tively accomplished with an offset that is 
slightly narrower labiolingually than in- 
cisocervically. The offset should follow the 
normal configuration of the incisal edge, and 
its transition into the proximal flares should 
be smooth and continuous. An inverted-cone 
diamond or carbide (Fig. 10-32) can be used 
to prepare the offset. 

6. Place a pinhole in the cingulum area slightly 
off center to improve the retention and resis- 
tance form of this preparation. The pinhole is 
prepared in five stages: first, a small horizon- 
tal ledge is made with a large, tapered carbide 
bur; second, a slight "dimple" is created with 
a round bur at the intended pinhole location; 
third, a pilot hole is prepared with a small-di- 



ameter twist drill* (it must be parallel to the 
precise path of withdrawal of the restoration); 
fourth, the preparation is completed with a ta- 
pered carbide bur to a pinhole depth of ap- 
proximately 2 mm; finally, a larger, round bur 
is used to countersink or bevel the junction 
between pinhole and ledge. 
The technical aspects of pinhole preparation are 
described in the ensuing paragraphs. The com- 
pleted preparation (Fig. 10-33) is carefully assessed 
for any remaining undercuts. The flares are a com- 
mon area for undercuts, and all surfaces should be 
smoothed as previously described. 

PINLEDGE PREPARATIONS 

A pinledge (Fig. 10-34) is occasionally used as a sin- 
gle restoration, generally to reestablish anterior 
guidance, in which case only the lingual surface is 
prepared. More commonly, however, it is used as a 
retainer for a fixed partial denture (Fig. 10-35) or to 
spHnt periodontally compromised teeth (Fig. 10-36). 
In these cases, one or more of the proximal surfaces 
are included in the preparation design to accommo- 
date the required connector(s). Retention and resis- 
tance are provided primarily by pins that extend to 
a depth of 2 mm into dentin. Compared to other re- 
tainers, the pinledge preparation is very conserva- 
tive of tooth structure. 

The preparation steps themselves are not diffi- 
cult, but advance planning and a thorough under- 
standing of the various steps are prerequisites to 
success. Diagnostic preparation on an accurate cast 
is particularly useful during the planning phase. 
Preparation of a number of parallel pinholes with 
a common path of withdrawal can be intimidating. 
With some practice, however, this can be accom- 
plished freehand by most operators, especially 
when a tapered bur is used. Paralleling devices are 
available for practitioners who do not feel com- 
fortable preparing multiple pinholes. Generally, 
pinledges are highly esthetic restorations. Plaque 
control after treatment is easier because of short 
margin length and largely supragingival margin 
location. 

Indications. The pinledge is indicated for un- 
damaged anterior teeth in dentitions with a low 
caries experience. The presence of a small proximal 
carious lesion, however, does not preclude its use. If 
a high esthetic requirement exists, the advantage 
of this restoration is that the labial tooth surface 



*The twist drills supplied with threaded pin kits for 
amalgam retention are suitable. 



I 



Section 2 Clinical Procedures-Part I 





Fig. 1 0-33. A, Completed three-quarter crown preparation on a maxillary canine. B, The contralateral 
canine. C, A three-quarter crown serves as the anterior retainer for a three-unit FPD; its female intracoro- 
nal RPD rest is incorporated in the mesial box. D, Note the connector and the open embrasures on the 
contralateral side. E to G, Labial views of the cemented FPDs. H, The definitive RPD. 




Fig. 1 0-34. The pinledge preparation on a maxillary central incisor. A, Guiding grooves placed for 
lingual reduction. B, The lingual reduction completed and an incisal bevel placed. C, Incisal and cervical 
ledges prepared. D, Indentations have been made. Note the spacing of the ledges relative to each other 
and to the pulp. All pinholes will be in sound dentin. E, Pinholes prepared to a depth of 2 mm. The junc- 
tion between the ledge and the pinholes has been countersunk. 



rh^pter 10 The Pnrti^l Veneer Trnwri, Tnlny, nnd Onl^y Preparations 
A B C 



I 




Fig. 1 0-35. A, Modified pinledge serving as a retainer for a four-unit FPD. An additional pinhole was 
placed in the cingulum and in the cervical aspect of the proximal groove; in the latter instance, this was 
done because insufficient tooth structure remained to provide resistance against lingual displacement. 
B, The FPD on the master cast. C, A four-unit FPD consisting of a modified pinledge, two metal-ceramic 
pontics, and a metal-ceramic crown. 




D 



Fig. 1 0-36. A, Periodontally compromised but caries-free teeth of adequate buccolingual width are 
excellent candidates for a pinledge retained fixed splint. B, The master cast. C, Pinledge splint consisting 
of six separate castings that were soldered together and seated. D, A minimum display of metal results. 
The pinledge preparations permit retention of the intact labial enamel of all six anterior teeth. 



remains intact, although this is sometimes offset by 
the display of a slight amount of metal along the in- 
cisal edge. Pinledges can be prepared on bulbous 
teeth that are unsuitable for three-quarter crowns, 
which \vould result in a significant amount of 
unsupported enamel interproximally. The lingual 
concavity of a maxillary anterior tooth can be modi- 
fied successfully with a pinledge restoration (see Fig. 
10-22) to establish the desired anterior guidance. 

Contraindications. Patients with poor oral hy- 
giene or a high caries rate are not good candidates 



for this type of restoration. Young patients with large 
pulps generally are better served by a resin-retained 
FPD (see Chapter 26). Often it is not possible to place 
pinholes of adequate size and length in teeth that are 
thin labiolingually (Fig. 10-37). Pinledges are con- 
traindicated on nonvital teeth and when the align- 
ment of the abutment will conflict with the proposed 
path of withdrawal of the fixed partial denture. Be- 
cause less surface area is involved in the prepara- 
tion, pinledges are not as retentive as their less con- 
servative counterparts. Therefore they should not be 
used when optimum retention is needed. 



I 



Section 2 Clinical Procedures-Part I 



Maxillary Central Incisor Pinledge. Three de- 
signs of pinledge preparations are discussed here: 
the conventional pinledge (see Fig. 10-34), involving 
only the lingual surface of the tooth; the pinledge 




Fig. 1 0-37. Where incisors are thin labiolingually and 
insufficient dentin remains facial to the casting, appearance 
is compromised by a pinledge restoration. 




Fig. 1 0-38. Pinledge preparation with a proximal slice. 
The slice provides room for an FPD connector. Sufficient 
tooth structure should remain between the slice and the 
pinhole adjacent to it. Note that the junction between pin- 
hole and ledge has been beveled or countersunk. 



with a proximal slice (Fig. 10-38); and the pinledge 
with a proximal groove (Fig. 10-39, A). The latter 
two can serve equally well as retainers for an FPD; 
choosing one over the other depends primarily on 
tooth configuration and the presence or absence of 
caries. A tooth with a slight proximal convexity can 
often be prepared successfully with a proximal slice, 
whereas one with a small carious lesion often lends 
itself better to the proximal groove variation. The 
pinledge preparation with proximal slice is de- 
scribed first. 

Design 

1. Draw the outline of the proposed preparation 
onto the tooth (Fig. 10-40). A line is marked 
along the height of contour of the incisal edge 
and on the proximal wall to include the area 
needed for a connector. The lingual chamfer 
is placed immediately adjacent to the crest of 
the marginal ridge. The cervical extent of the 
margin is on the height of contour of the cin- 
gulum, but it may be extended farther cervi- 
cally at a later stage to blend into the proxi- 
mal aspect of the preparation. 

Proximal Reduction 

2. Prepare the proximal slice with a tapered di- 
amond. (Disks may be preferred by some op- 
erators.) The diamond is either held parallel 
to the path of withdrawal or given a slight 
lingual inclination. The primary purpose of 
this step is to provide sufficient reduction to 
allow adequate metal in the area for a subse- 
quent connector. The proximal reduction in- 
cludes the proximal contact area, but care 




Fig. 1 0-39. A, Modified pinledge preparation with a proximal groove. The path of withdrawal of this 
groove is compatible with the preparation as well as with the pinholes. B, A similar preparation on a 
maxillary canine. Note two similarities with the three-quarter crown: the heavy lingual chamfer and the 
incisal offset blending into the proximal groove to provide additional bulk for reinforcement. 



Chapter 10 The Partial Veneer Crown, Inlay, and Onlay Preparations 



I 



must be taken not to extend the reduction too 

far facially, because this will alter the outline 
form of the tooth. For esthetic reasons, the 
reduction must not extend onto the labial 
surface. 

Incisal and Lingual Reduction 

3. Prepare the incisal bevel with the diamond 
inclined slightly toward the lingual. It ex- 
tends just beyond the previously placed pen 
oil line on the crest of the incisal edge, but it 
must remain within the curvature of the in- 
cisal edge to minimize display of metal. Suf- 
ficient clearance provides functional contact 
on metal rather than on the junction between 
metal and tooth structure. The desired metal 
thickness is 1 mm, except in the area close to 
the margin. 

4. Perform the Ungual reduction with a football- 
er wheel-shaped diamond after placing re- 
duction grooves as has been described in 
other anterior preparations. Metal thickness 
of 1 mm is required in the intercuspal posi- 
tion and throughout excursive movements. 
The reduction follows the lingual marginal 



5. 



ridge and continues its chamfer configura- 
tion cervically until it runs into the proximal 
reduction. To facilitate subsequent stages of 
the preparation, care must be taken to main- 
tain as much tooth structure as possible in the 
incisal third. 

Smooth the incisal and lingual reduction 
with fine-grit diamonds and stones before 
preparing the ledges and pinholes. 



Ledges and Indentations. Two ledges are pre- 
pared across the reduced lingual surface. They will 
provide room for sufficient bulk of metal to ensure 
rigidity. The restoration would otherwise not be 
very strong because it would consist of only a thin 
sheet of metal. 

The ledges are prepared parallel to the incisal 
edge of the tooth as viewed from the lingual and 
parallel to one another as viewed from the incisal. In 
selected areas they will be widened to provide in- 
dentations of sufficient size to accommodate the 
pinholes. The determination of the incisocervical lo- 
cation of the ledges depends on the configuration of 
the pulp and the available bulk of tooth structure 
(Fig. 10-41). Usually the incisal ledge is prepared 2 




Fig. 10-40. A, Although periodontally compromised and malpositioned, these six caries-free anterior 
teeth are excellent for pinledge preparations. B, Orthodontic repositioning of the teeth. C, Stabilization 
after the repositioning. D, Outline of the proposed preparations drawn on the teeth. 



I 



Section 2 Clinical Procedures-Part I 




Fig. 10-41 . Proximal lingual view of the location of ledges relative to the height of the crown. The in- 
cisal ledge is placed so its floor is one fourth of the preparation's height from the incisal edge. The cervi- 
cal ledge is placed so its floor bisects the cervical fourth. Note that the path of insertion is parallel to the 
incisal two thirds of the labial wall. Adequate offset of the cervical pinhole either mesially or distally is 
needed to prevent pulpal exposure. 



to 2.5 mm cervical to the incisal edge, or one fourth 
of the total height of the preparation from the incisal 
edge. The cervical ledge is placed on the crest of the 
cingulum at the center of the cervical one fourth of 
the preparation. 

6. Prepare two ledges with a cylindrical carbide 
bur. The recommended minimum width for 
the ledge is 0.7 mm. Drawing the proposed 
location of the ledges on the lingual surface 
of the tooth is helpful. The design of the 
ledges must be compatible with the path of 
withdrawal of the restoration, which is paral- 
lel to the incisal two thirds of the labial sur- 
face of the tooth. 

7. Make indentations in the left and right sides 
of the incisal ledge and slightly off center in 
the cervical ledge to prevent subsequent pulp 
exposure when the pinholes are placed. 
These incisal indentations will be as widely 
spaced as possible to retain as much dentin as 
possible between the pinholes and the pulp. 
Because the completed pinhole must be sur- 
rounded by sound dentin, it is not possible to 
place holes in the extreme comers because of 
the tooth's morphology. However, every ef- 
fort should be made to prepare the indenta- 
tions so that the pinholes will be surrounded 
by dentin and away from the pulp. This is 
particularly important for younger patients. 
The relationship between recommended pin- 
hole locations and the pulp is illustrated in 
Fig. 10-42. Generally this means that the in- 
dentations are just within the mesial and dis- 
tal marginal ridges, about 1.5 mm inside the 
external tooth contour (Fig. 10-43). The same 
carbide bur can be used to prepare the inden- 



tations. When completed, the configuration 
of the indentations should resemble a half 
cylinder. Again, their orientation is parallel to 
the selected path of withdrawal and their 
floor should be smooth and continuous with 
the floor of the ledges. When combined, they 
should provide a flat area 1 to 1.2 mm wide 
buccolingually. 

Pinhole Preparation 

8. Sink pilot channels with either a small, round 
bur or a small twist drill. The shallow inden- 
tations will prevent skating of the selected 
bur. The depth of the completed pinhole 
should be at least 2 mm but can be as much 
as 3 mm when the placement and orientation 
of the pilot channels are satisfactory. 

9. Enlarge and deepen the pilot channels with a 
tapered carbide bur when their placement 
and orientation are satisfactory. At this stage, 
any small corrections in orientation can be 
made. Less experienced operators may 
spend a great deal of time attempting to de- 
termine the correct alignment of the bur. 
However, it should be remembered that the 
design and location of the pinholes have al- 
ready been determined by the placement of 
the ledges and indentations, so the only re- 
maining concern should be verification of 
the position of the rotary instrument and at- 
tainment of the minimum depth of the pin- 
holes. Some operators find it helpful to place 
a second bur in a prepared pinhole to help 
transfer the path of withdrawal, although 
precautions must be taken to prevent its be- 
ing swallowed or inhaled. Preparing multiple 



A, B 



50-S9 
30-39 
20-29 
10-19 
Years 



Mamillary Centraf Incisor 
Pjnl^ge Preparation 



Maxtlbiy Lateral Incisat 
Pin [edge Preparation 



Maxillary Canine 
l*Jn!edge Prepa ration 




D,E 



Cross lecticm 
4.7 mm from tndsa( Fdge 




Cross s«cHon 

3.9 mm from Incisat Edge 




Cross section 
4,4 mm from IncJ^af Edge 




Cervical Level 



Cervfcal Level 



Cervical Level 



C,H 






Fig. 1 0-42. Relationship between pinliole placement and pulp configuration. A to C, Lingual view. 
D to F, Cross section through incisal pinholes. G to I, Cross section through cervical pinholes. Dotted 
lines show the mean pulp chamber size of various age groups. 
(Data from Ghashi Y. Shikagakuho 68:726,1968.) 




Fig. 10-43. A, Proposed location of the ledges marked on the teeth with a pencil. Note the orienta- 
tion of the carbide relative to the long axis of the tooth. B, Ledge preparation completed on one side. 
Pilot holes for some pinholes have been placed. 



I 



10. 



Section 2 Clinical Procedures- Part I 

pinholes a little at a tinne nnay also be 
helpful, moving from one to the next and 
gradually deepening each. This will permit 
alignment verification as the pinholes are 
prepared. 

Bevel the junction between pinhole and in- 
dentation with a round bur slightly larger 



than the largest diameter of the pinhole (Fig. 
10-44). (The required interproximal clear- 
ance is illustrated in Fig. 10-45.) 
Inspect all surfaces of the preparation for 
smoothness and evaluate the margin. Cor- 
rect any area that requires more distinct de- 
lineation (Fig. 10-46). 




1 mm- 



J K- 



0.5 mm 7—^ 



1 mm — l^ 



Fig. 1 0-44. Note the relation among the ledge, the indentation, and the pinhole. Recommended di- 
mensions are given in the buccoHngual cross section on the right, a, Ledge; b, indentation; c, pinhole; 
d, countersink. 





Fig. 1 0-45. Modified pinledge preparation with a proximal groove. Adequate interproximal clear- 
ance has resulted from the proximal flare. 



A ■;;^ 




Fig. 1 0-46. A, Ledges and indentations pre- 
pared. B, Pinhole preparation with low-speed 
handpiece. C, The completed pinledge prepara- 
tions. Utility wax has been placed over the brack- 
ets for impression making. 



Chapter 10 The Partial Veneer Crown, Inlay, and Onlay Prpparations 



I 



I NLAYS AND ONLAYS 

INDICATIONS 

An inlay can be used instead of amalgam for pa- 
tients with a low caries rate who require a small 
Class II restoration in a tooth with ample support- 
ing dentin. It is among the least complicated cast 
restorations to make and can be very durable when 
it is carefully done. An onlay allows the damaged 
occlusal surface to be restored with a casting in the 
most conservative manner. It should be considered 
in the restoration of a severely worn dentition when 
the teeth are otherwise minimally damaged or for 
the replacement of an MOD amalgam restoration 
when sufficient tooth structure remains for reten- 
tion and resistance form. 

CONTRAINDICATIONS 

Since these restorations rely on intracoronal (wedg- 
ing) retention, inlays and onlays are contraindi- 
cated unless there is sufficient bulk to provide 
resistance and retention form. MOD inlays may in- 
crease the risk of cusp fracture and are generally 
not recommended. Extensive onlays, required 
where caries or existing restorations extend beyond 
the facial or lingual line angles, are contraindicated 
unless pins are used to supplement retention and 
resistance. 

ADVANTAGES 

Cast inlays and onlays can prove to be extremely 
long-lived restorations because of the excellent me- 
chanical properties of the gold alloy. Low creep and 
corrosion mean that if inlay or onlay margins 
are accurately cast and finished, they will not dete- 
riorate. The lack of corrosion may be an esthetic 
advantage. Gold will not lead to the tooth dis- 
coloration sometimes associated with dental 
amalgam. Unlike an inlay or amalgam, an onlay 
can support cusps, reducing the risk of tooth 
fracture. 



PREPARATION 

Armamentarium (Fig. 10-47). Carbide burs are 
usually used for inlay or onlay preparations, but di- 
amonds can be substituted if preferred: 

• Tapered carbide burs 

• Round carbide burs 

• Cylindrical carbide burs 

• Finishing stones 

• Mirror 

• Explorer and periodontal probe 

• Chisels 

• Hatchet 

• Gingival margin trimmers 

• Excavators 

• High- and low- speed handpieces 

• Articulating film 



CLASS II INLAY PREPARATION 
Occlusal Analysis 



FIG. 10-48) 



1. Carefully assess the occlusal contact relation- 
ship and mark it with articulating film. The 
margins of the restoration should not be too 
close (<1.0 mm) to a centric contact; other- 
wise, there will be damaging stresses at the 
gold-enamel junction. 

2. Apply rubber dam. Because good visibility 
and moisture control are essential during 
tooth preparation and caries excavation, the 
use of a rubber dam is strongly recommended. 

Outline Form 

3. Penetrate the central groove just to the depth 
of the dentin (typically about 1.8 mm) with a 
small, round or tapered carbide bur held in 
the path of withdrawal of the inlay. Generally 
this will be perpendicular to an imaginary 
hue connecting the buccal and Ungual cusps, 
not necessarily perpendicular to the occlusal 
plane. For example, on mandibular premo- 
lars it will be angled toward the lingual. 



DISADVANTAGES 

In the restoration of a small carious lesion, an inlay 
is not very conservative of tooth structure. This is 
because additional tooth removal is necessary after 
minimal proximal extension to achieve a cavity 
preparation without undercuts and to permit access 
for impression making. This extension may lead to 
additional display of metal and gingival encroach- 
ment, which is undesirable for periodontal health. 
Since they do not encircle the tooth, inlays rely on 
the bulk of the buccal and lingual cusps for resis- 
tance and retention form. There is concern that high 
occlusal force will lead to cusp fracture due to 
wedging from the inlay. 




Fig. 10-47. Armamentarium for inlays and onlays. 



I 



Section 2 Clinical Procedures- Part I 




Fig. 10-48. The MO inlay preparation. A, Deptli lioie extending just into tlie dentin. B, An occlusal 
outline is prepared following the central groove. C, The outline is extended proximally and then gingi- 
vally, undermining the marginal ridge and removing caries. D, Unsupported enamel is removed, and 
the walls of the proximal box are defined. This is easily accomplished with hand instruments. E, Proxi- 
mogingival bevels can be placed with tapered or flame-shaped carbides and hand instruments. F, An oc- 
clusal bevel or chamfer complete the preparation. G, Occlusal view of the completed preparation. 




B 



Fig. 1 0-49. Preparation of a mandibular molar tooth for 
an MO inlay. A, Occlusal outline. B, Proximal box initiated. 
C, Proximal box extended to remove contact. D, Completed 
preparation. 

(Courtesy Dr. H. Bowman.) 

4. Extend the occlusal outline through the cen- 
tral groove with the tapered carbide. The bur 
should be held in the same path of with 
drawal and kept at the same depth just into 



dentin. The buccolingual extension should be 
as conservative as possible to preserve the 
bulk of the buccal and lingual cusps. Resis- 
tance to proximal displacement is achieved 
with a small occlusal dovetail or pinhole. The 
outline should avoid the occlusal contacts. 

5. Extend the outline proximally, undermining 
the marginal ridge, and stop it at the height of 
contour of the ridge (Fig. 10-49, A). 

6. Advance the bur cervically to the carious le- 
sion and then lingually and buccally, taking 
care to hold it in the precise path of with- 
drawal. There should be a thin layer of 
enamel remaining between the side of the bur 
and the adjacent tooth (Fig. 10-49, B). This 
will prevent accidental damage. The bur 
should move parallel to the original unpre- 
pared proximal surface, creating a convex ax- 
ial wall in the box. The opposing buccal and 
lingual walls contribute significantly to reten- 
tion, so great care must be taken not to tilt the 
bur during this step. It should be held in the 
path of withdrawal throughout. The width of 
the gingival floor of the box should be about 



Chapter 10 The Partial Veneer Crown, Inlay, and Onlay Preparations 



I 



1.0 mm (mesiodistally). Correct cervical, lin- 
gual, and buccal extension at this stage is 
just beyond the proximal contact area. The 
completed inlay will require a minimum of 
0.6 mm of proximal clearance to allow an 
i mpression to be made, but some of this will 
be achieved with the proximal flares and 
gingival bevels. Sharp line angles between 
the occlusal outline and proximal box are 
rounded at this time (Fig. 1 0-49, C). 

Caries Excavation 

7. Identify and remove any caries not elimi- 
nated by the proximal box preparation, us- 
ing an excavator or a round bur in the 
low-speed handpiece. 

8. Place a cement base to restore the excavated 
tissue in the axial wall and/or pulpal floor. 
If necessary, the preparation can be ex 
tended buccally or lingually. NOTE: an inlay 
is not a suitable restoration for extensive 
caries, and carrying it beyond the line an- 
gles will lead to a significant loss of reten- 
tion and resistance form. 

Axiogingival Groove and Bevel Placement 

9. Prepare a small, well-defined groove at the 
junction of axial and gingival walls at the 
base of the proximal box to enhance resis- 
tance form and prevent distortion of the 
wax pattern during manipulation. It is eas- 
ily placed with a gingival margin trimmer 
held in contact with the axial wall to prevent 
creating an undercut. 

10. Place a 45-degree gingival margin bevel 
with a thin, tapered carbide or fine-grit 
diamond. Correct orientation is achieved by 
holding the instrument parallel to the gingi- 
val one third of the proximal surface of the 
adjacent tooth. The bur should not be tilted 
buccally or lingually to the path of with- 
drawal; othenA/ise, an undercut will be cre- 
ated at the corners of the box (a commonly 
seen fault in inlay preparations). 

1 1 . Prepare proximal bevels on the buccal and 
lingual walls with the tapered bur oriented 
in the path of withdrawal. There should be a 
smooth transition between the proximal and 
gingival bevels. 

12. Place an occlusal bevel to improve marginal 
fit and allow finishing of the restoration. 
When the cuspal anatomy is steep, a con 
ventional straight bevel will create too little 
gold near the margin for strength and dura- 
bility. A hollow-ground bevel or chamfer is 



normally preferred and can be conveniently 
placed with a round bur or stone. 
13. As a final step, smooth the preparation 
where necessary, paying particular attention 
to the margin (Fig. 10-49, D). 

MOD ONLAY PREPARATION FIG. 10- 

The occlusal outline and proximal boxes of an onlay 
preparation are similar to those of an inlay. The ad- 
ditional steps are the occlusal reduction and a func- 
tional (centric) cusp ledge. 

Outline Form 

1. Prepare the occlusal outline with a tapered 
carbide bur just beyond the enamel-dentin 
junction (approximately 1.8 mm deep) and 
extend it through the central groove, incorpo- 
rating any deep buccal or lingual grooves. 
Existing amalgam restorations are removed 
as part of this step. 

2. Extend the outline both mesially and distally 
to the height of contour of the marginal ridge. 
As with an inlay, the boxes with an MOD on 
lay are prepared by advancing the bur gingi- 
vally and then buccally and lingually, always 
holding it in the precise path of withdrawal 
of the preparation. By ensuring that there is a 
thin section of proximal enamel remaining as 
the bur advances, damage to the adjacent 
tooth will be prevented (Fig. 10-51 , A). Cor- 
rect gingival, buccal, and lingual extension of 
the preparation normally depends on the 
contact area with the adjacent tooth. A mini- 
mum clearance of 0.6 mm is needed for im- 
pression making. Sometimes existing restora- 
tions or caries require a box to be extended 
beyond optimal. However, if a box requires 
extension beyond the transitional line angle, 
the preparation will have little resistance 
form, and an alternative restoration such as 
a complete crown should be considered. 
Preparing the boxes is a key step when fabri- 
cating an onlay. The tapered bur should be 
held precisely in the planned path of with- 
drawal throughout. Tilting, often caused by 
trying to advance the bur too quickly, is com- 
monly done and is difficult to correct. 

3. Round sharp line angles between the occlusal 
outline and proximal boxes. 

Caries Excavation 

4. Remove any remaining caries using an excava- 
tor or a round bur in the low-speed handpiece. 

5. Place a cement base to restore the excavated 
tissue. Good judgment is needed to ensure 



I 



Section 2 Clinical Procedures-Part I 
A ^--^^ B 





Fig. 10-50. The MOD onlay preparation. 
A, An occlusal outline is prepared to follow the 
central fossa, and the marginal ridges are un- 
dermined. B, The proximal boxes are refined. 
They should extend just beyond the proximal 
contact area. C, Depth grooves are placed for 
occlusal reduction-0.8 mm on the noncentric 
cusp and 1 .3 mm on the centric cusp. D, Note 
the lingual functional cusp bevel as part of the 
completed occlusal reduction. A lingual shoul- 
der is prepared, approximately at the level of 
the occlusal isthmus. E, Continuous bevel com- 
pletes the preparation. The bevel on the Lingual 
shoulder makes a smooth transition into the 
proximal bevel of the box. A small contrabevel 
is placed on the buccal cavosurface margin. 
F, Occlusal view of the completed preparation. 



B 




Fig. 1 0-51 . Preparation of a mandibular molar tooth for an MOD onlay. A, Preparation outline. 
B, Proximal boxes extended to remove contacts. C, Occlusal reduction grooves. D, Centric cusp ledge 
placed for distal half. E and F, Completed preparation. 
(Courtesy Dr. H. Bowman.) 



Chapter 10 The Partial Veneer Crown, Tn1ay, and Onlay Preparations 



I 



that adequate sound dentin is present on the 
axial walls to provide retention and resistance. 

Occlusal Reduction 

6. Place depth grooves on the centric (func- 
tional) cusps. To give additional clearance at 
the cusp tip, the bur must be oriented more 
horizontally than the intended restoration 
cusp. The grooves should be 1.3 mm deep, 
allowing 0.2 mm for smoothing. 

7. Place 0.8 mm grooves on the noncentric 
cusps. On noncentric cusps, the bur is ori- 
ented parallel to the cuspal inclines. As with 
all depth grooves, it is assumed that the 
tooth is in good occlusal relation before 
preparation. If it is not, a vacuum- formed 
matrix made from the diagnostic waxing 
procedure is recommended as a guide. 

8. Connect the grooves to form the occlusal re- 
duction, maintaining the general contour of 
the original anatomy. 

9. Prepare a 1.0-mm centric cusp ledge with 
the cylindrical carbide bur (Fig. 10-51, D). 
This will give the restoration bulk in a 
high-stress area, preventing deformation 
during function. The ledge should be placed 
about 1 mm apical to the opposing centric 
contacts. It extends into the proximal boxes 



but should not be positioned too far api- 
cally; otherwise, the resistance form from 
the boxes will be lost. 

10. Round any sharp line angles, particularly 
at the junction of the ledge and occlusal 
surface. 

11. Check for adequate occlusal reduction by 
having the patient close into soft wax and 
measuring with a thickness gauge. 

Margin Placement 

12. Estabhsh a smooth, continuous bevel on all 
margins. The gingival bevel is placed, as for 
an inlay, with the thin carbide or diamond 
held at 45 degrees to the path of with- 
drawal, or approximately parallel to the ad- 
jacent tooth contour. This will blend 
smoothly with the buccal and lingual 
bevels, which have been prepared with the 
bur held in the path of withdrawal. 

13. Bevel the noncentric and centric cusps. 
Where additional bulk at the margin is 
needed, a chamfer should be substituted for 
the straight bevel. This can be placed with a 
round-tipped diamond. 

14. Complete the preparation by rechecking the 
occlusal clearance in all excursions and as- 
sessing for smoothness (Fig. 10-51, E and F). 



Sf^dtf QiiC^iiom 



are the indications and contraindications for partial veneer crowns? 
are the advantages and disadvantages of partial veneer crowns? 

is the recommended armamentarium and in what sequence should o maxillary premolar be pre- 
fer a partial veneer crown? 

ore the minima! criteria for each step described above? 
are the indications and contraindications for inlay/onlay restorations? 
ore the advantages and disadvantages For inlay/onlay restorations? 

is the recommended armamentarium and in what sequence should a mandibular molar be prepared 
inlay/onlay restoration? 
are the minimal criteria for each step described above? Why? 



1. 


What 


2. 


What 


3. 


What 




pored 


4. 


What 


5. 


What 


6. 


What 


7. 


What 




For an 


8. 


What 




Section 2 Clinical Procedures-Part 



■summary chart 



Indications 



Contraindications 



Sturdy clinical crown of average 
lengtfi or longer 

Intact buccal surface not in need 
of contour modification and 
well-supported by sound 
tooffi structure 

No conflict between axial rela- 
tionsfiip of tooth and pro- 
posed path of witfidrawal 
ofFPD 



Short teeth 
High caries index 
Extensive desfrucHon 
Poor aiignmertt 
Bulbous tee^h 
Thin teeth 



Advantages 



Conservafive of tootfi struc- 
ture 

Easy access to margins 

Less gingival involvement 
than with complete cast 
crown 

Easy escape of cement and 
good seating 

Verification of seating simple 

Electric vitality test feosible 



Disadvantages 



Less retentive dian complete 
cast crown 

Limited adjustment of path 
of withdrawal 

Some display of metal 



I 



SUMMARY CHART 



Indications 



Contraindications 



Sturdy clinical crown of overage 
length or longer 

Intact iabiol surface that is not in 
need of contour modificotion 
and thot is supported by 
sound tooth structure 

No discreponcy between axial 
relationship of toofh ond pro- 
posed patfi of withdrowol 

of FPD 



Short teeth 

Nonvital feetfi 

High cories index 

Extensive destruction 

Poor alignment with path of 
wiriidrowal of FPD 

Cervical caries 

Bulbous teeth 

Tliin teeth 



Advantages 



Disadvantages 



Conservation of toorii 
structure 

Easy access to margins for 
finishing (dentist) and 
cleaning (potientj 

Less gingival involvement 
than with complete cost 
crown 

Easy escape of cement and 
good seoting 

Easy verification of complete 
seating 

Electric vitality test feasible 



Less retentive than complete 
cast crown 

Limited odjustment of path 
of insertion 

Some dispby of metal 

Not indicated on nonvital 

teeth 



Chapter 10 The Partial Veneer Crown, Inlay, and Onby Prep^rntions 



■ 



Partial Veneer Crown PREPARArroN, Posterior Teeth 




Recommended 




Preparation Steps 


Armamentarium 


Criteria 


Depth grooves for occiusol 
reduction 


Tapered carbide fissure bur 
or tapered roundtipped 
diamond 


0.8 mm on noncentnc cusps 
1 .3 mm on centric cusps 


Occiusol reduction 


Round-tipped diamond 


Clearance of 1 mm on noncentric cusps, 1 .5 mm on centric 
cusps 


Depth grooves for axial 
reduction 


Round-tipped diamond 


Chomfer depth of 0.5 mm (no more than half the width of 
diamond) 


Axial reduction 


Round-tipped diamond 


Axioi reduction parollel to long axis of tooth 


Chamfer frnishing 


Large, round-tipped diamond 


Smooth and continuous to minimize marginal length and facili- 
tate finishing; distinct resistance to vertical displacement by 
periodontal probe 


Proximal groove 


Tapered carbide fissure bur 


Distinct resistance to lingual displacement by probe; parallel to 
path of withdrawal of restoration; 90~degree angle between 
prepared axial wall and buccal or lingual aspect of groove 


Buccal and occlusal bevel 
(maxillae), chamfer 
(mandible) 


Round-tipped diamond 


Maxillary teeth: bevel extends just beyond cusp tip but remains 

within curvature of cusp tip 
Mandibular teeth: minimum of 1 mm of cost gold in area of 

centric stops 


Finishing 


Large, round-tipped diamond 

or carbide 


All sharp internal tine angles (except grooves) rounded to 
smooth transitions 



Partial Veneer Crown Preparation^ Anterior Teeth 



Preparation Steps 



Recommended 
Armamentarium 



Criteria 



Depth grooves for lingual 
reduction 

Lingual reduction 

Incisol bevel 

Depth grooves for axial 
reduction 

Axial reduction 



Retention form (proximal 
grooves ond lingual 
pinhole) 



Finishing and flare 



Round-tipped diamond 

Football-shaped diamond 
Round-tipped diamond 
Round-tipped diamond 

Round-tipped diamond 



Tapered carbide fissure bur 
and half-round bur 



Fine-grit; tapered diamonds 
(large and small) or 

carbide 



Should allow for "t mm of clearance 

Should hove 1 mm of clearance 

Allows for metal thickness >0.7 mm 

Allows for 0.5 mm of metal thickness at margin 

Extends into interproximal about 0,4 mm lingual of contact 
area; parallel to incisal two thirds of labial surface 

Grooves parallel to incisa! two thirds of labial surface; should 
resist lingual displacement; pinhole should be between 2 
and 3 mm deep 

Lingual wall of groove meefs proximoaxial wall at angle of 90 
degrees 

AH surfaces smooth; buccal wall of groove flared to break 
proximal contact; resulting cavosurface angle h 90 de- 
grees; no unsupported enamel remaining 



Spntinn p r.iininai Procediires-Pajli 



ISUMMARY CHART 



Indications 



Contraindkations 



Advantages 



Disadvantages 



Undamaged ontenor teeth in 
caries- free mouth 

Alteration af lingual contour of 
maxillary anterior teeth or ol- 
tefotion of occlusion 

Anterior splinting 



Large pulps 

Thin teeth 

Nonvital teeth 

Carious involvement 

Problems with proposed 
path of withdrawal of 
FPD 



Minimal tooth reduction 

Minimal margin iength 

Minimum gingival 
involvement 

Optimum access for margin 
finishing ond hygiene 

Adequate retention 



Less retentive than complete 
coverage 

Alignment can prove difficult 

Technically denionding 

Not usoble on nonvital leetli 



ISUMMARY CHART 



Indications 



Contraindications 



Advantages 



Disadvantages 



Small corlous lesion in otherwise 
sound tooth 

Adequate dentinal support 

Low caries rate 

Potient's request for gold instead 
of omalgam or composite 
resin 



High caries index 

Poor plaque control 

Smoil teeth 

Adolescents 

MODs 

Poor dentinal support 
requiring a v^ide 
preporalion 



Superior material properties 

Longevity 

No discoloration frorn 
corrosion 

Least complex cast 

restoration 



Less conservative than 
amalgam 

May display metal 

Gingival extension beyorid 
ideal 

"Wedge" retention 



ISUMMARY CHART 



Indications 



Contraindications 



Advantages 



Disadvantages 



Worn or carious teeth with in- 
tact buccal and lingual cusps 

MOD amalgam requiring 
replacement 

Low caries rate 

Patient's request for gold instead 
of amalgam 



High caries index 

Poor ploque control 

Short clinical crown or ex- 
truded teeth 

Lesions extending beyond 
transitional line angles 



Support of cusps 
High sJrength 
Longevity 



Lacks retention 

Less conservoHon than 
amalgam 

May display metal 

Gingival extension beyond 
ideal 



Chapter 10 The Partial Veneer Crown, Inlay, and Onlay Preparations 



PiNLEDGE Preparation 




Recommended 




Preparation Steps 


Armamentarium 


Criteria 


Reduction of marginal ridge 
and contact areo od jo- 
cent to edentulous space 


Round'tipped, tapered 
diamond 


Should provide space for adequate bulk of metal in area of 
connector 


Lingual reducHon 


Football -shaped diamond 


Should provide for clearance of at leost 0,7 mm 


Ledges 


Straight carbide fissure bur 


Ledges must be parollel to one another when viewed fronn lin- 
gual and from incisal; maximum width 1 mm 


Indentations 


Straight carbide fissure bur 


Indentation should provide at least 0.5 mm of space For metal 
reinforcement around opening of pinhole 


Pilot channels and pinholes 


Tapered carbide bur 


Pinholes musf be between 2 and 3 mm deep; minimol widtli of 
ledge around pinholes is 0.5 mm 


Finishing 


Finishing stones or carbides 


All surfaces must be as smooth as possible (obtain with fine- 
grit rotary instruments) to facilitate removal of this delicate 
wax pattern from die 



Class II Inlay Preparation 




Recommended 




Preparation Steps 


Armamentarium 


Criteria 


Occlusal outline 


Tapered carbide 


Includes central groove, avoids centric contacts, includes dove- 
toil or pinhole for resistance; approx, 1 .8 mm deep 


Proximal box 


Tapered carbide 


Follows curvature of original tooth surface 


Caries removal 


Excavator or round bur 


Tissue replaced with base 


Axiogingivol groove 


Gingival margin trimmer 


Detectable witli explorer tip (0.2 mm deep) 


Gingival and proximal 
bevels 


Thin, tapered carbide or 
diamond 


45 degrees; approximately 0,8 mm wide 


Occlusal bevel 


Round carbide or stone 


Hollow ground, avoid centric contacts. 



Mod Onlay Preparation 


Preparation Steps 


Recommended 
Arma me nta ri um 


Criteria 


Occlusal outline 
Proximal boxes 


Tapered carbide 
Tapered carbide 


Includes cenhrai, buccal, and lingual grooves; about 1 .8 mm 
deep 

Follows curvature of original tooth surface 


Cories removal 


Excavator or round bur 


Tissue replaced with base 

Adequate dentin for resistonce and retention 


Occlusal reduction 


Tapered carbide 


Following anatomic contours 

1 .5-mm centric cusp; 1 .0-mm noncentric cusp 


Centric cusp ledge 


Tapered carbide 


About 1 .0 mm wide (before beveling} 
About 1.0 mm apicol to centric contact 


Gingival and proximal 
bevels 


Thin^r tapered carbide 


45 degrees; about 0.8 mm wide 



Tooth Preparation for 
All-Ceramic Restorations 



All-ceramic inlays, onlays, veneers, and crowns are 
some of the most esthetically pleasing prosthodontic 
restorations. Because there is no metal to block light 
transmission, they can resemble natural tooth struc- 
ture better in terms of color and translucency than 
any other restorative option. Their chief disadvan- 
tage is their susceptibility to fracture, although this 
is lessened by use of the resin-bonded technique. 

The restorations may be fabricated in several 
ways. The technique (first developed over 100 years 
ago) originally called for a platinum foil matrix to 
be intimately adapted to a die. This supported the 
porcelain during firing and prevented distortion. 
The foil was removed before cementation of the 
restoration. 

Today, popular fabrication processes for the 
restorations include hot-pressing and slip-casting. 
These options are discussed in Chapter 25. 

COMPLETE CERAMIC CROWNS 

Complete ceramic crowns should have relatively 
even thickness circumferentially. For the hot- 
pressed ceramic crown (IPS Empress* or Optimalt) 
(Fig. 11-1) usually about 1 to 1.5 mm is needed to 

*lYOclar-AG: Schaan, Liechtenstein. 
tjeneric/Pentron, Inc: Wallingford, Conn. 



1 mm 



1.5 mm 




1 mm 



Fig. 11-1. 
crown. 



Recommended reduction for the all-ceramic 



create an esthetically pleasing restoration. Incisally, 
a greater ceramic thickness may be required. 

Only minor differences in tooth preparation de- 
sign exist among the restorations fabricated with 
the various techniques. Therefore, the hot-pressed 
crown preparation is described in detail, and the 
necessary variations are discussed when pertinent. 

ADVANTAGES 

The advantages of a complete ceramic crown in- 
clude its superior esthetics, its excellent translu- 
cency (similar to that of natural tooth structure), 
and its generally good tissue response. Lack of rein- 
forcement by a metal substructure permits slightly 
more conservative reduction of the facial surface 
than is possible with the metal-ceramic crown, al- 
though the lingual surface needs additional reduc- 
tion for strength. The appearance of the completed 
restoration can be influenced and modified by se- 
lecting different colors of luting agent. However, 
changing cement color under restorations that rely 
on an opaque core for strength, such as the slip cast 
alumina core system (InCeram*), will be ineffective. 

DISADVANTAGES 

The disadvantages of a complete ceramic crown in- 
clude reduced strength of the restoration because of 
the absence of a reinforcing metal substructure. Be- 
cause of the need for a shoulder-type margin cir- 
cumferentially, significant tooth reduction is neces- 
sary on the proximal and lingual aspects. Porcelain 
brittleness, when combined with the lack of a rein- 
forcing substructure, requires the incorporation of a 
circumferential support with a shoulder. Thus, by 
comparison, the proximal and lingual reductions 
are less conservative than those needed for a 
metal- ceramic crown. 

Difficulties may be associated with obtaining a 
well-fitting margin when certain techniques are 
used. The "unforgiving" nature of porcelain, if an 



*Vita Zahnfabrik: Bad Sackingen, Germany. 



262 



Chapter 1 1 Tooth Preparation for All-Ceramic Restorations 



I 



inadequate tooth preparation goes uncorrected, can 
result in fracture. 

Proper preparation design is critical to ensuring 
mechanical success. A 90-degree cavosurface angle 
is needed to prevent unfavorable distribution of 
stresses and to minimize the risk of fracture (Fig. 
11-2). The preparation should provide support for 
the porcelain along its entire incisal edge. Thus a se- 
verely damaged tooth (Fig. 11-3) should not be re- 
stored with a ceramic crown. 

All-ceramic restorations are not effective as re- 
tainers for a fixed partial denture, although the 
strongest of the slip-cast materials (In-Ceram zirco- 
nia) and the higher- strength pressed systems (IPS 
Empress 2) may be suitable for anterior applications. 
The brittle nature of porcelain requires that connec- 
tors of large, cross-sectional dimension (a minimum 
of 4 X 4 mm is recommended) be incorporated in the 
FPD design. Typically this leads to impingement on 
the interdental papilla by the connector, with in- 
creased potential for periodontal failure. 




Margm design should 
result in iavorable stress 
distribution. 



Fig. 11-2. A sloping shoulder is not recommended for 
the all-ceramic crown. It does not support the porcelain. In- 
cisal loading will lead to tensile stresses near the margin. 




Wear has been observed on the functional sur- 
faces of natural teeth that oppose porcelain restora- 
tions. This also applies to teeth opposed by 
metal-ceramic restorations, especially the mandibu- 
lar incisors, which can exhibit significant wear over 
time (see Fig 17-1). 

INDICATIONS 

The complete ceramic crown is indicated in areas 
with a high esthetic requirement where a more con- 
servative restoration would be inadequate (Fig. 
11-4). Usually such a tooth has proximal and/or fa- 
cial caries that can no longer be effectively restored 
with composite resin. The tooth should be relatively 
intact with sufficient coronal structure to support 
the restoration, particularly in the incisal area, 
where it is important not to exceed a maximum 
porcelain thickness of 2 mm; otherwise, brittle fail- 
ure of the material will occur. 

Because of the relative weakness of the restora- 
tion, the occlusal load should be favorably distrib- 
uted (Fig. 11-5). Generally this means that centric 
contact must be in an area where the porcelain is 




Fig., 11-3. Removal of an existing anterior crown. De- 
fects in this tooth make it unsuitable for an all-ceramic 
crown. 



Fig. 1 1 -4. A, Inadequately fitting all-ceramic crowns 
have led to recurrent caries and gingival recession around 
these central incisors. The patient, a professional model, 
had a high esthetic requirement. B, The gingival defect was 
corrected by minor periodontal recontouring, the teeth 
were reprepared, and new all-ceramic crowns were 
provided. 




Section 2 Clinical Procedures-Part I 




Fig. 1 1 -5. The occlusion on an all-ceramic crown is criti- 
cal for avoiding fracture. Centric contacts are best confined 
to the middle third of the lingual surface. Anterior guid- 
ance should be smooth and consistent with contact on the 
adjacent teeth. Leaving the restoration out of contact is not 
recommended. Future eruption may lead to protrusive in- 
terferences, precipitating fracture. 




Fig. 11-6. Unfavorable occlusal loading such as this 
edge-to-edge relationship on the lateral incisor is a con- 
traindication to the all-ceramic crown, particularly in view 
of the parafunctional activity of this patient. 



supported by tooth structure (e.g., in the middle 
third of the lingual wall). 

CONTRAINDICATIONS 

The ceramic crown is contraindicated when a more 
conservative restoration can be used. Rarely are they 
recommended for molar teeth. The increased oc- 
clusal load and the reduced esthetic demand make 
metal- ceramics the treatment of choice. If occlusal 
loading is unfavorable (Fig. 1 1-6) or if it is not possi- 
ble to provide adequate support or an even shoulder 
width of at least 1 mm circumferentially, a metal- 
ceramic restoration should be considered instead. 




Fig. 11-7. Armamentarium for an all-ceramic crown 
preparation. 





B 



Note the rounded 
interna J line angles. 



Fig. 1 1 -8. All-ceramic crown preparation. A, Labial 
view. B, Lingual view. To prevent stress concentrations in 
the ceramic, all internal line angles should be rounded. The 
shoulder should be as smooth as possible to facilitate the 
technical aspects of fabrication. 

PREPARATION 

Armamentarium (Fig. 11-7). The instruments 
needed for preparing a ceramic crown include the 
following: 

• Narrow, round-tipped, tapered diamonds, reg- 
ular and coarse grit (0.8 mm) 

• Square-tipped, tapered diamond, regular grit 
(1.0 mm) 

• Football-shaped diamond 

• Finishing stones and carbides 

• Mirror 

• Periodontal probe 

• Explorer 

• Chisels and hatchets 

• High- and low-speed handpieces 

Step-by-Step Procedure (Fig. 11-8). The prepa- 
ration sequence for a ceramic crown is similar to 
that for a metal-ceramic crown; the principal differ- 
ence is the need for a 1 -mm- wide chamfer circum- 
ferentially (Fig. 11-9). 



Chapter 1 1 Tooth Preparation for AII-CeTamic Restorations 



I 




Fig. 11-9. Note the uniform chamfer width of 1 mm on 
this aU-ceramic crown preparation. 



Incisal (Occlusal) Reduction. The completed 
reduction of the incisal edge should provide 1.5 to 2 
mm of clearance for porcelain in all excursive move- 
ments of the mandible. This will permit fabrication of 
a cosmetically pleasing restoration with adequate 
strength. If the restoration is used for posterior teeth 
(rare), 1.5 to 2 mm of clearance is needed on all cusps. 

1. Place three depth grooves in the incisal edge, 
initially keeping them approximately 1.3 mm 
deep to allow for additional loss of tooth 
structure during finishing. The grooves are 
oriented perpendicular to the long axis of the 
opposing tooth to provide adequate support 
for the porcelain crown. 

2. Complete the incisal reduction, reducing half 
the surface at a time, and verify its adequacy 
upon completion. 

Facial Reduction 

3. After placing depth grooves, reduce the facial 
or buccal surface and verify that adequate 
clearance exists for 1 mm of porcelain thick 
ness. One depth groove is placed in the mid- 
dle of the facial wall, and one each in the 
mesiofacial and distofacial transitional line 
angles. The reduction is then performed with 
a cervical component parallel to the proposed 
path of withdrawal and an incisal component 
parallel to the original contour of the tooth. 
The depth of these grooves should be ap- 
proximately 0.8 mm to allow finishing. The 
reduction is performed on half of the facial 
surface at a time. 

4. Do the bulk reduction with the round-tipped 
tapered diamond (which will result in a 
heavy chamfer margin). Be sure to maintain 
copious irrigation throughout. 

Lingual Reduction 

5. Use the football-shaped diamond for lingual 
reduction after placing depth grooves ap- 
proximately 0.8 mm deep. The lingual reduc 
tion is done like the other anterior tooth 
preparations (see Chapters 9 and 10) until a 
clearance of 1 mm in all mandibular excur- 



sive movements has been obtained. Ade- 
quate space must exist for the porcelain in all 
load-bearing areas. 

6. After the selected path of withdrawal has 
been transferred from the cervical wall of the 
facial preparation, place a depth groove in 
the middle of the cingulum wall. 

7. Repeat the shoulder preparation, this time 
from the center of the cingulum wall into the 
proximal, until the lingual shoulder meets 
the facial shoulder. This margin should fol- 
low the free gingival crest and should not ex- 
tend too far subgingivally. 

Chamfer Preparation. For subgingival mar- 
gins, displace the tissue with cord before proceed- 
ing with the chamfer preparation. The ultimate ob- 
jective is to direct stresses optimally in the 
completed porcelain restoration. This is accom- 
phshed when the chamfer or rounded shoulder 
margin completely supports the crown; then any 
forces exerted on the crown will be in a direction 
parallel to its path of withdrawal. A sloping shoul- 
der will result in unfavorable loading of the porce- 
lain, with a greater likelihood of tensile failure. A 
90-degree cavosurface angle is optimal. Care must 
be taken, however, that no residual unsupported 
enamel is overlooked, because it might chip off. 

The completed chamfer should be 1 mm wide, 
smooth, continuous, and free of any irregularities. 

Finishing 

8. Finish the prepared surfaces to a final 
smoothness as described for the other tooth 
preparations. Be sure to round any remaining 
sharp line angles to prevent a wedging ac- 
tion, which can cause fracture. 

9. Perform any additional margin refinement as 
needed, using either the diamond or a car- 
bide rotary instrument of choice. 

CERAMIC INLAYS AND ONLAYS 

For patients demanding esthetic restorations, ce- 
ramic inlays and onlays provide a durable alternative 
to posterior composite resins. The procedure consists 
of bonding the ceramic restoration to the prepared 
tooth with an acid-etch technique. The bonding 
mechanism relies on acid etching of the enamel and 
the use of composite resin, as seen in the resin- 
retained FPD technique (see Chapter 26). Bonding to 
porcelain is achieved by etching with hydrofluoric 
acid and the use of a silane coupling agent (materials 
are identical to those marketed as porcelain repair 
kits). A similar restoration uses indirectly fabricated 
composite resin instead of the ceramic inlays. 



I 



Section 2 Clinical Procedures-Part I 



INDICATIONS 

A ceramic inlay can be used instead of amalgam or 
a gold inlay for patients with a low caries rate re- 
quiring a Class II restoration and wishing to restore 
the tooth to its original appearance. It is the most 
conservative ceramic restoration and enables most 
of the remaining enamel to be preserved. 

CONTRAINDICATIONS 

Because these restorations are time consuming and 
expensive, they are contraindicated in patients with 
poor oral hygiene or active caries. Because of their 
brittle nature, ceramics may be contraindicated in 
patients with excessive occlusal loading, such as 
bruxers. 

ADVANTAGES 

Ceramic inlays and onlays can be extremely esthetic 
restorations. The restoration wear associated with 
posterior composite restorations is not a problem 
with the ceramics. Marginal leakage associated with 
polymerization shrinkage and high thermal coeffi- 
cient of expansion of the resin is reduced, because 
the luting layer is very thin. 

DISADVANTAGES 

Accurate occlusion can be difficult to achieve with 
ceramic inlays and onlays. Because they are fragile, 
intraoral occlusal adjustment is impractical before 
they are bonded to place. Therefore, any areas of ad- 
justment need careful finishing and polishing. 



which is a time-consuming procedure. Rough 
porcelain is extremely abrasive of the opposing 
enamel. Castable glass-ceramics (see Chapter 25) 
are less abrasive than the traditional feldspathic 
porcelain. Wear of the composite resin-luting agent 
can be a problem, leading to marginal gaps. These 
will eventually allow chipping or recurrent caries. 
Accuracy is important with these restorations, be- 
cause accurately fitting restorations (marginal gaps 
less than 100 u m) have been shown to reduce this 
problem significantly. Finishing of the margins can 
be difficult in the less accessible interproximal areas. 
Resin flash or overhangs are difficult to detect and 
can initiate periodontal disease. 

Bonded ceramic inlays are a relatively new con- 
cept, and long-term clinical performance is hard to 
judge. The patient should always be made aware 
that unforeseen problems may surface over time 
when a newer procedure is used. 

PREPARATION (FIG 1 1-10) 

Armamentarium (Fig 11-11). As for metal in- 
lays, carbide burs are used in the preparation, but 
diamonds may be substituted: 

• Tapered carbide burs 

• Round carbide burs 

• Cylindrical carbide burs 

• Finishing stones 

• Mirror 

• Explorer and periodontal probe 

• Chisels 




Fig. 11 -10. Maxillary first molar preparation for an MOD ceramic inlay. A, Defective restoration. 

B, The restoration and caries removed. C, Unsupported enamel removed and glass ionomer base placed. 

D, The completed ceramic restoration. 

(Courtesy Dr. R. Seghi.) 



Chapter 1 1 Tooth Preparation for A11-Ce,raTnic Restorations 




• Gingival margin trimmers 

• Excavators 

• High- and low-speed handpieces 

• Articulating film 

Step-by-Step Procedure. Rubber dam isolation 
is recommended for visibility and moisture control. 
Before applying the dam, mark and assess the oc- 
clusal contact relationship with articulating film. To 
avoid chipping or wear of the luting resin, the mar- 
gins of the restoration should not be at a centric 
contact. 

Outline Form 

1. Prepare the outline form. This will generally 
be governed by the existing restorations and 
caries and is broadly similar to that for con 
ventional metal inlays and onlays (see Chap- 
ter 10). Because of the resin bonding, axial 
wall undercuts can sometimes be blocked out 
with resin-modified glass ionomer cement, 
preserving additional enamel for adhesion. 
However, undermined or weakened enamel 
should always be removed. The central 
groove reduction (typically about 1.8 mm) 
follows the anatomy of the unprepared tooth 
rather than a monoplane. This will provide 
additional bulk for the ceramic. The outline 
should avoid occlusal contacts. Areas to be 
onlayed need 1.5 mm of clearance in all ex- 
cursions to prevent ceramic fracture. 
Extend the box to allow a minimum of 0.6 
mm of proximal clearance for impression 
making. The margin should be kept supra 
gingival, which will make isolation during 
the critical luting procedure easier and will 
improve access for finishing. If necessary, 
electro surgery or crown lengthening (p. 150) 
can be done. The width of the gingival floor 
of the box should be approximately 1 .0 mm. 



2. 




3. Round all internal line angles. Sharp angles 
lead to stress concentrations and increase the 
likelihood of voids during the luting procedure. 

Caries Excavation 

4. Remove any caries not included in the out- 
line form preparation with an excavator or a 
round bur in the low- speed handpiece. 

5. Place a resin-modified glass ionomer cement 
base to restore the excavated tissue in the gin- 
gival wall. 

Margin Design 

6. Use a 90-degree butt joint for ceramic inlay 
margins. Bevels are contraindicated because 
bulk is needed to prevent fracture. A distinct 
heavy chamfer is recommended for ceramic 
onlay margins. 

Finishing 

7. Refine the margins with finishing burs and 
hand instruments, trimming back any glass 
ionomer base. Smooth, distinct margins are 
essential to an accurately fitting ceramic 
restoration. 

Occlusal Clearance (for Onlays) 

8. Check this after the rubber dam is removed. 
A 1.5-mm clearance is needed to prevent frac- 
ture in all excursions. This can be easily eval 
uated by measuring the thickness of the resin 
provisional restoration with a dial caliper. 

PORCELAIN LAMINATE VENEERS 

Laminate veneering (Fig. 11-12) is a conservative 
method of restoring the appearance of discolored. 




Fig. 11 -11 . Armamentarium for the porcelain laminate 
veneer preparation. 



Fig. 11 -12. Esthetic facial veneers. A, Discolored maxil- 
lary central incisors. B, Prepared for porcelain veneers. 
C, The laminates etched before bonding. D, Restorations in 
place. 
(Courtesy Dr. C. Zmick.) 



I 



Section 2 Clinical Procedures-Part I 



pitted, or fractured anterior teeth. It consists of 
bonding thin ceramic laminates onto the labial sur- 
faces of affected teeth. The bonding procedure is the 
same as that for ceramic inlays. 

ADVANTAGES AND INDICATIONS 

The main advantage of facial veneers is that they are 
conservative of tooth structure. Typically only about 
0.5 mm of facial reduction is needed. Since this is 
confined to the enamel layer, local anesthesia is not 
usually required. The main disadvantage of the pro- 
cedure relates to difficulty in obtaining restorations 
that are not excessively contoured. This is almost in- 
evitable in the gingival area if enamel is left for 
bonding. Currently, little has been reported about 
the effect of the restorations on long-term gingival 
health and whether or how often they will need re- 
placement over a patient's lifetime. 

Esthetic veneers should always be considered as 
a conservative alternative to cemented crowns. In 
many practices they have largely replaced metal- 
ceramic crowns for the treatment of multiple discol- 
ored but otherwise sound teeth. 



PREPARATION 

Armamentarium. The instruments needed for 
preparing a porcelain laminate veneer include the 
following: 

• 1-mm round bur or 0.5-mm depth cutter 

• Narrow, round-tipped, tapered diamonds, reg- 
ular and coarse grit (0.8 mm) 

• Finishing strip 

• Finishing stones 

• Mirror 

• Periodontal probe 

• Explorer 

Step-by-Step Procedure (Fig. 11-13). The gingi- 
val third and proximal line angles are often over- 
contoured with these restorations. Therefore, maxi- 
mum reduction should be achieved with minimum 
penetration into the dentin. 

1. Make a series of depth holes with a round 
bur to help avoid penetrating abnormally 
thin enamel. The required amount of reduc 
tion will depend somewhat on the extent of 
discoloration. A minimum of 0.5 mm is usu- 



C,D 




Fig. 11 -13. Porcelain facial veneer preparation. A, The proximal contact areas and incisal edge are 
preserved, and the preparation is limited to enamel. Normally a reduction depth of about 0.5 mm is rec- 
ommended, but making a series of depth holes with a round bur will guard against penetrating thin 
enamel. B, Tetracycline- stained teeth. Composite resin veneers were placed earlier but failed to mask the 
discoloration satisfactorily. Six maxillary porcelain labial veneers will be provided. C and D, Completed 
tooth preparations. E, Provisionals made directly with composite resin, which are retained by etching 
small areas of enamel (see Chapter 15). 



Chapter 1 1 Tooth Preparation for All-Ceramic Restorations 



I 



ally adequate. The reduction should follow 
the anatomic contours of the tooth. 

2. Place the "long chamfer" margin (Fig. 11-14). 
This design has an obtuse cavosurface angle, 
which exposes the enamel prism ends at the 
margin for better etching. The margin should 
closely follow the gingival crest so that all 
discolored enamel will be veneered without 
undue encroachment on the gingival sulcus. 

3. Wherever possible, place the preparation 
margin labial to the proximal contact area to 
preserve it in enamel. However, slight clear- 
ance for separating the working cast and for 
accessing the proximal margins for finishing 
and polishing is essential. A diamond finish- 
ing strip helps create the necessary clearance. 
Sometimes the proximal margins are ex- 
tended lingually to include existing restora- 
tions. This can necessitate considerable tooth 



reduction to avoid creating an undercut. 
Some authorities advocate placing the ce- 
ramic margin on composite rather than ex- 
tending the preparation to enamel, but this 
is not recommended. Extensive existing 
restorations are a contraindication for porce- 
lain laminate veneers. 

4. If possible, do not reduce the incisal edge 
(Fig. 11-15); this helps support the porcelain 
and makes chipping less likely. If the incisal 
edge length is to be increased, the prepara- 
tion should extend to the lingual. Care is 
needed to avoid undercuts with this modifi- 
cation. Visualizing the path of insertion of the 
restoration is important, because an undercut 
will prevent placement of the veneer. 

5. To prevent areas of stress concentration in the 
porcelain, be sure that all prepared surfaces 
are rounded (see Fig. 11-13, C, D). 




Fig. 11 -14. The recommended margin ("long chamfer") 
for facial veneers has an obtuse cavosurface angle so the 
ends of the enamel prisms will be exposed for differential 
etching. 



[7 



'y ^fc^iiofiK 



Preferred 




Modified 



Fig. 11 -15. The preferred design for porcelain laminate 
veneers maintains part of the incisal edge in enamel. If the 
edge is to be lengthened, a modified preparation with lin- 
gual extension will be needed (dotted line). 



!• What are the indications and confraindications For all-ceramic crowns and porcelain laminate veneers? 

2. What are the advantages and disadvantages for alkeramic crov^^ns and porcelain laminate veneers? 

3. What is the recommended armamentarium, and in what sequence should a maxillary central incisor be 
prepared for an all<;eramic crown and porcelain laminate veneer? 

4. What ore the minimal criteria for each step described above? Why? 

5. Discuss the advantages, disadvantages, indications, and contraindications for ceramic inlays and oniays. 

6. What is the recommended armamentarium, and in what sequence should a mandibular molar be pre- 
pared for Q ceramic inlay and onlay? 

7. What are the minimal criteria for each step described above? Why? 



I 



Section 2 Clinical Procedures-Part I 



ISUMMARYr^JA^ 



Indications 



High esthetic requirement 

Considerable proximal caries 

Incisal edge reosonobly intoct 

Endodontfcatly treated teeth 
with post-and-cores 

Fovorable distribution of 
occlusal load jl 



Contraindications 



V^^en superior strength is 

warranted and metal^ceramic 
crown is more appropriate 

High caries index 

I rii sufficient coronal tooth struc- 
ture for support 

Thin teeth faciolinguolly 

Unfavorable dislribution of oc- 
clusal load 

Bruxism 



Advantages 



Disadvantages 



Estheticall/ unsurpassed Reduced strength compared 
Good tissue response even *^ metal-ceramic crown 

for subgingival margins Proper preparation ex- 
Slightly more conservative ^''^'^^V ^^riticol 

of facial wall than Among least conservative 
metol ceramic preparations 

Brittle nature of material 

Con be used as single 
restoration only 



■summary Chil^ 



Indications 



Demand for esthetics 

Low caries rate 

Intact buccal and lingual 
enamel 



Contraindications 



High caries index 
Poor plaque control 
Bruxism 



Advantages 



Superior esthetics 

Conservative 

Durable 



Disadvantages 



Abrasive of opposing tooth 

Occlusion difficult to adjust 

Wear of luting agent 

Expensive 

Long-term success rate 
unknown 



[SUMMARY gim! 



Indications 



Contraindications 



Discolored or damaged 
anterior teeth 



Advantages 



High caries index 
Poor ploque confrol 
Extensive existing restorations 
Bruxfsm 



Superior esthetics 
Wear and stoin resistant 



Disadvantages 



Increased tooth contour 
Expensive 



Chapter 1 1 Tooth Preparation for All-Ceramic Restorations 



I 





All-Ceramic Crown Preparation 








Recommended 






Preparation Steps 


Annamentarium 


Criteria 




Depth grooves for incisal 
reduchon 


Tapered diamond 


Approximotel)^ 1 .3 mm deep to allow for additional reduction 
during finishing; perpendicular to long axis of opposing 
tooth 




Incisal reduction 


Tapered diamond 


Clearance of 1 .5 mm; check excursions 




Depth grooves for foclal 
reduction 


Tapered diamond 


Depth of 0.8 mm needed for additional reduction during 
finishing 




Facial reduction 


Tapered diamond 


Reduction of 1 .2 mm needed; two planes, as for metal-ceramic 
crown preparation 




Depth grooves and lingual 
reduction 


Tapered and football -shaped 
diamonds 


Initial depth 0.8 mm; recreate concave configuration; do not 
maintain any convex configurations (stress) 




Deptfi grooves for cingufum 
reduction 


Tapered diamond 


Parallel to cervical aspect of facial preparation; 1 mm of re- 
duction; shoulder follows free gingival margin 




Lingual shoulder preparation 


Square-tipped diamond 


Rounded shoulder 1 mm wide; minimize "peaks and valleys"; 
90-degree cavosurfoce angle 




Finishing 


Fine-grit diamond or 
carbide 


All surfaces smooth ond continuous; no unsupported enamel; 
90-degree covosurface angle 



Ceramic Inlay and 


Onlay Preparation 








Recommended 






Preparation Steps 


Ami amen tari urn 


Criteria 




Outline 


Tapered carbide 


Includes existing restorations and cqries; obout \ .8 mm deep; 
smoll undercuts tolerated 


Proximal box 


Tapered corbide 


Gingival Hoor 1 mm wide 
Clearance for impression 0.6 mm 




Caries removal 


Excavator or round bur 


Block out undercuts with glass ionomer 




Margins 


Finishing burs 
Hand instruments 


90-degree butt joint 
Heavy chomfer br onlays 




Occlusal clearance 


Round-tipped diamond 


Clearance in oil excursfons of 1 .5 mm 




Finishing 


Finishing burs 
Fine-grit diomonds 


Rounded internal angles 
Smooth margins 





Porcelain Laminate Veneers 




Recommended 




Preparation Steps 


Armamentarium 


Criteria 


Depth cuts 


] -mm round bur or 0,5-mm 
depth cutter 


A series of depth cuts to determine dentin exposure 


Facial reduction 


Round-tipped diamond 


Follows curvahjre of original tooth surface 


Proximal reduction 


Round-tipped diamond 


Extended to gingival crest, leaving contoct area intact 


Incisal and lingual reduction 


Round^tipped diamond 


None unless incisal margin is extended to lingual to allow 
[engthening 


Margins 


Round-tipped diamond 


Long chamfer 


Finishing 


Fine-grit diamonds, car- 
bides, or finishing stones 


No sharp internal morgins 



CHAPTER 



T W E L V 



Restoration of the Endodontically 

Treated Tooth 



canal configuration 

embedment depth 

ferrule 

multipiece post-and-cores 

post-and-core 

post configuration 

post removal 



post type 

prefabricated posts 
root diameter 
stress distribution 
surface texture 
tooth length 



An endodontically treated tooth should have a 
good prognosis. It can resume full function and 
serve satisfactorily as an abutment for a fixed or re- 
movable partial denture. However, special tech- 
niques are needed to restore such a tooth. Usually a 
considerable amount of tooth structure has been 
lost because of caries, endodontic treatment, and the 
placement of previous restorations. The loss of 
tooth structure makes retention of subsequent 
restorations more problematic and increases the 
likelihood of fracture during functional loading. 

Two factors influence the choice of technique: the 
type of tooth (whether it is an incisor, canine, premo- 
lar, or molar) and the amount of remaining coronal 
tooth structure. The latter is probably the most im- 
portant indicator when determining the prognosis. 

Different clinical techniques have been proposed 
to solve these problems, and opinions vary about 
the most appropriate one. Recent experimental data 
have improved our understanding of the difficulties 
inherent in restoring an endodontically treated 
tooth. This chapter offers a rational and practical ap- 
proach to the challenge. 

TREATMENT PLANNING 

Extensive caries or periodontal disease may make 
removal of a tooth more sensible than endodonti- 
cally treating it, although a severely damaged tooth 
occasionally can be restored after orthodontic repo- 
sitioning or root resection (Fig. 12-1). This should be 
done if its loss will significantly jeopardize the pa- 



tient's occlusal function or the total treatment plan, 
particularly if dental implants are not an option. 
When the decision is made to treat the tooth en- 
dodontically, consideration must have been given to 
its subsequent restoration. Before restoration, exist- 
ing endodontically treated teeth need to be assessed 
carefully for the following': 

• Good apical seal 

• No sensitivity to pressure 

• No exudate 

• No fistula 

• No apical sensitivity 

• No active inflammation 

Inadequate root fillings should be retreated. If 
doubt remains, the tooth should be observed until 
there is definite evidence of success or failure. 

If the coronal structures are largely intact and 
loading is favorable as on anterior teeth that are far- 
ther removed from the fulcrum, a simple filling can 
be placed in the access cavity (Fig. 12-2, A). However, 
if a substantial amount of coronal structure is miss- 
ing, a cast post-and-core is indicated instead (Fig. 
12-2, B). Molars are often restored with amalgam or a 
combination of one or more cemented posts and 
amalgam or composite resin (Fig. 12-2, C and D). 

Although one-piece post-crowns were once 
made, such prostheses are of historical interest only. 
Superior results can now be obtained with a two- 
step technique (Fig. 12-3) consisting of a post-and- 
core foundation and a separate crown. Most often a 
metal post is used, which provides the necessary re- 
tention for the core. This replaces any lost coronal 
tooth structure of the tooth preparation. The shape 
of the residual coronal tooth structure, combined 
with the core, should result in an ideal shape for the 
preparation (Fig. 12-4). 

Prefabricated metal, carbon fiber, ceramic, and 
glass fiber posts are available. These last two op- 
tions provide esthetic alternatives to metal posts. 23 
They are used in conjunction with a plastic material 
such as composite resin, amalgam, or glass ionomer. 

With the two-step approach of fabricating a sepa- 
rate crown over a cast post-and-core, achieving a 



272 



Chapter 12 Restoration of the Endodontically Treated Tooth 



I 




Fig. 12-1. A to C, A severely damaged tooth can sometimes be retained after orthodontic extrusion 
(see Chapter 6). D and E, Plaque control around periodontally compromised teeth may be improved af- 
ter hemisectioning (see Chapter 5). 

(D and E courtesy Dr. H. Kahn.) 






Fig. 1 2-2. A, An anterior tooth with intact clinical crown can be predictably restored with a compos- 
ite restoration in the access cavity. B, When most coronal tissue is missing, a cast post-and-core is indi- 
cated to obtain optimal tooth preparation form. C, In mandibular molars an amalgam foundation is sup- 
ported by a cemented prefabricated post in the distal canal. D, In maxillary molars the palatal canal is 
most often used. 



satisfactory marginal fit is easier because the expan- 
sion rate of the two castings can be controlled indi- 
vidually. A cast post-and-core needs to be slightly 
smaller than the canal to achieve optimal internal 



seating, whereas the crown needs to be slightly 
larger to achieve optimal seating (see Chapter 7). 
The two-step approach further permits fabrication 
of a replacement crown, if necessary, without the 



I 



Section 2 Clinical Procedures-Part I 




Fig. 1 2-3. A, The first molar and second premolar have 
been restored with post-and-cores. Note the margins, opti- 
mally located on sound tooth structure, cervical to the cast- 
ings. B, Extracoronal restorations in place. 




Fig. 1 2-4. The second premolar has been restored with a 
cast post-and-core, before a metal-ceramic crown. 

(Courtesy Dr. R. Webber.) 



need for post removal. Finally, a different path of 
placement than the one selected for the post-and- 
core may be selected for the crown. This is often 
helpful when the tooth is restored to serve as an 
abutment for a fixed partial denture (FPD). 

CLINICAL FAILURE 

Morphologic and functional differences between an- 
terior teeth and posterior teeth require that they be 
treated differently after endodontic therapy, mainly 
because different loading considerations apply. 

One retrospective analysis' involving 638 patients 
evaluated 788 post-and-cores: 456 custom cast post- 
and-cores and 332 foundations with ParaPosts. Four 
to five years after cementation, reported failure rates 
in males were significantly higher than in females, 
and failure rates above age 60 were three times as 
high as failure rates for younger patients. Maxillary 
failure rates (15%) were three times as high as 
mandibular failure rates (5%), and more prevalent in 
lateral incisors, canines, and premolars than central 



incisors and molars. Failure rate under fixed partial 
dentures was significantly lower than under single 
crowns. The latter may be due to load reduction re- 
sulting from bracing by the FPD. No correlation was 
apparent between failure and reduced marginal 
height of the encasing bone. Custom cast post- 
and-cores exhibited slightly higher failure rates 
than amalgam foundations. This observation was 
also made by Sorensen and Martinoff. However, 
Torbjorner et al4 suggest that custom cast post-and- 
cores tend to be used more often in teeth that already 
have considerably weakened root structure. Thus, 
regardless of the technique selected for subsequent 
restoration, the teeth themselves are already more 
prone to failure. Distal cantilevers appear to con- 
tribute to post-and-core failure in endodontically 
treated abutment teeth that support the cantilever. 
Most of the failures just discussed are influenced 
by load. In general, as loading increases, failure rates 
appear to increase concomitantly. Failure loads have 
been shown to increase as the load angle approaches 
parallelism to the long axes of the teeth . 6 This sug- 
gests that failure will occur more readily under 
lateral loading. When planning the restoration of en- 
dodontically treated teeth, the practitioner's progno- 
sis must consider the strength of the remaining tooth 
structure weighed carefully against the load to 
which the restored tooth will be subjected. 

CONSIDERATIONS FOR ANTERIOR TEETH 

Endodontically treated anterior teeth do not always 
need complete coverage by placing a complete 
crown, except when plastic restorative materials 
have limited prognosis (e.g., if the tooth has large 
proximal composite restorations and unsupported 
tooth structure). Many otherwise intact teeth 
function satisfactorily with a composite resin 
restoration. 

Although commonly believed, it has not been 
demonstrated experimentally that endodontically 
treated teeth are weaker or more brittle than vital 
teeth. Their moisture content, however, may be re- 
duced.' Laboratory testing' has actually revealed a 
similar resistance to fracture between untreated and 
endodontically treated anterior teeth. Nevertheless, 
clinical fracture does occur, and attempts have been 
made to strengthen the tooth by removing part of 
the root canal filling and replacing it with a metal 
post. In reality, placement of a post requires the re- 
moval of additional tooth structure (Box 12-1), 
which is likely to weaken the tooth. 

Cementing a post in an endodontically treated 
tooth is a fairly common clinical procedure despite 
the paucity of data to support its success. In fact, a 
laboratory study and two stress analyses'", " have 



Chapter 12 Restoration of the Endodontically Treated Tooth 



I 




Tt'Tiiion 




N(M4lrdl axis 



Compression 



Fig. 1 2-5. Experimental stress distributions in an en- 
dodontically treated tooth with a cemented post. When the 
tooth is loaded, the lingual surface is in tension, and the fa- 
cial surface is in compression. The centrally located ce- 
mented post lies in the neutral axis (i.e., not in tension or 
compression). 

(Redrawn from Guzy GE, NichoUs JI: J Prosthet Dent 42:39, 

1979.) 



Disadvantages to the Routine Use 
OF A Cemented Post box 1 2- 1 



Piacing the post requires an additional operative 
procedure. 

Prepraring a tooth to occommodate the post removes ad- 
ditional tooth structure. 

It may be difficult to restore the tooth later, when a com- 
plete crown is needed, because the cemented post may 
have failed to provide adequate retention for the core 
material 

The post can complicote or prevent future endodontic re- 
trealment if this becomes necessary. 



determined that no significant reinforcement re- 
suhs. This might be explained by the hypothesis 
that, when the tooth is loaded, stresses are greatest 
at the facial and Ungual surfaces of the root and an 
internal post, being only minimally stressed, does 
not help prevent fracture (Fig. 12-5). Other studies, 
however, contradict this assumption . 8,12 Cemented 
posts may further limit or complicate endodontic 
retreatment options if these are necessary. In addi- 
tion, if coronal destruction occurs, post removal 
may be necessary to provide adequate support for a 
future core. 

For these reasons, a metal post is not recom- 
mended in anterior teeth that do not require com- 
plete coverage restorations. This view is supported 
by a retrospective study that did not show any im- 
provement in prognosis for endodontically treated 




It takes some practice to 
estimate remaining wall 
thickness after preparation 
for the future extracoronal 
restoration. 



Weak arei? 



Fig. 1 2-6. Cross section through a central incisor. The 
dotted line indicates the original tooth contour before 
preparation for a metal-ceramic restoration. Even with min- 
imum reduction for the extracoronal restoration, note the 
weakened facial wall, which would not be able to support a 
prosthesis successfully. The sharp lingual wall compHcates 
pattern fabrication. 



anterior teeth restored with a post. In another study, 
post placement did not influence the position or an- 
gle of radicular fracture." 

Discoloration in the absence of significant tooth 
loss may be more effectively treated by bleaching'-' 
than by the placement of a complete crown, al- 
though not all stained teeth can be bleached suc- 
cessfully. Resorption can be an unfortunate side ef- 
fect of nonvital bleaching. ^ However, when loss of 
coronal tooth structure is extensive or the tooth will 
be serving as an FPD or RPD abutment, a complete 
crown becomes mandatory. Retention and support 
then must be derived from within the canal because 
a limited amount of coronal dentin remains once the 
reduction for complete coverage has been com- 
pleted. Coupled with the loss of internal tooth struc- 
ture necessary for endodontic treatment, the re- 
maining walls become thin and fragile (Fig. 12-6), 
often requiring their reduction in height. 

CONSIDERATIONS FOR POSTERIOR TEETH 

Endodontically treated posterior teeth are subject to 
greater loading than anterior teeth because of their 
closer proximity to the transverse horizontal axis. 
This, combined with their morphologic characteris- 
tics (having cusps that can be wedged apart), makes 
them more susceptible to fracture. Careful occlusal 
adjustment will reduce potentially damaging lateral 



I 



Section 2 Clinical Procedures-Part I 





Fig. 1 2-7. A, Mandibular premolar and hemisected mo- 
lar restored with cast post-and-cores. B, Waxed three-unit 
FPD. C, The FPD cemented in place. 

(Courtesy Dr. F Hsu.) 



forces during excursive movements. Nevertheless, 
endodontically treated posterior tooth should re- 
ceive cuspal coverage to prevent biting forces from 
causing fracture. Possible exceptions are mandibu- 
lar premolars and first molars with intact marginal 
ridges and conservative access cavities not sub- 
jected to excessive occlusal forces (i.e., posterior dis- 
clusion in conjunction with normal muscle activity). 
Complete coverage is recommended on teeth 
with a high risk of fracture. This is especially true 
for maxillary premolars, because complete coverage 
gives the best protection against fracture, since the 
tooth is completely encircled by the restoration. 
However, considerable tooth reduction is required, 
particularly when a metal-ceramic restoration is to 
be used. When significant coronal tooth loss has oc- 
curred, a cast post-and-core (Fig. 12-7) or an amal- 
gam foundation restoration is needed. 



m PRINCIPLES OF TOOTH 
PREPARATION 

Many of the principles of tooth preparation dis- 
cussed in Chapter 7 apply equally to the prepara- 
tion of endodontically treated teeth, although cer- 
tain additional concepts must be understood to 
avoid failure. 

CONSERVATION OF TOOTH STRUCTURE 

Preparation of the Canal (Fig. 12-8). When cre- 
ating post space, great care must be used to remove 
only minimal tooth structure from the canal. Exces- 
sive enlargement can perforate or weaken the root, 
which then may split during cementation of the post 
or subsequent function. The thickness of the remain- 
ing dentin is the prime variable in fracture resistance 
of the root. Experimental impact testing of teeth with 
cemented posts of different diameters' showed that 
teeth with a thicker (1.8 mm) post fractured more 
easily than those with a thinner (1.3 mm) one. 

Photoelastic stress analysis also has shown that 
internal stresses are reduced with thinner posts. 
Conversely, the root can be compared to a ring. The 
strength of a ring is proportional to the difference 
between the fourth powers of its internal and exter- 
nal radii. This implies that the strength of a pre- 
pared root comes from its periphery, not from its in- 
terior, so a post of reasonable size should not 
weaken the root significantly." Nevertheless, it is 
difficult to enlarge a root canal uniformly and to 
judge with accuracy how much tooth structure has 
been removed and how thick the remaining dentin 
is. Most roots are narrower mesiodistally than faci- 
olingually and often have proximal concavities that 
cannot be seen on a standard periapical radiograph. 
Experimentally, most root fractures originate from 
these concavities because the remaining dentin 
thickness is minimal. Therefore the root canal 
should be enlarged only enough to enable the post 
to fit accurately yet passively while ensuring 
strength and retention. Along the length of the post 
space, enlargement seldom needs to exceed what 
would have been accomplished with one or two ad- 
ditional file sizes beyond the largest size used for 
endodontic treatment. Because of the more coronal 
position of the post space, a much larger file must be 
used to accomplish this (Fig. 12-9). 

Preparation of Coronal Tissue. Endodontically 
treated teeth often have lost much coronal tooth 
structure as a result of caries, of previously placed 
restorations, or in preparation of the endodontic ac- 
cess cavity. However, if a cast core is to be used, fur- 
ther reduction is needed to accommodate a com- 
plete crown and to remove undercuts from the 



Chapter 12 Restoration of the RnHoHontirnlly TrenteH Tooth 



I 



• Apical seal 

' Minimai enlargement 

• Length 
' Stop 

• An ti rota Hon 

' Mar^n desi^ 




Fig. 1 2-8. Faciolingual cross section through a maxillary 
central incisor prepared for a post-and-core. Six features of 
successful design are identified: 1, Adequate apical seal; 

2, minimum canal enlargement (no undercuts remaining); 

3, adequate post length; 4, positive horizontal stop (to mini- 
mize wedging); 5, vertical wall to prevent rotation (similar 
to a box); 6, extension of the final restoration margin onto 
sound tooth structure. 




Fig. 1 2-9. Use of a prefabricated post entails enlarging 
the canal one or two file sizes to obtain a good fit at a pre- 
determined depth. A, Incorrect; the prefabricated post is 
too narrow. B, Incorrect; the prefabricated post does not ex- 
tend to the apical seal. C, Correct; the prefabricated post is 
fitted by enlarging the canal slightly. 



chamber and internal walls. This may leave very lit- 
tle coronal dentin. Every effort should be made to 
save as much of the coronal tooth structure as pos- 
sible, because this helps reduce stress concentra- 
tions at the gingival margin." The amount of re- 
maining tooth structure is probably the single most 
important predictor of clinical success. If more than 
2 mm of coronal tooth structure remains, the post 
design probably has a limited role in the fracture re- 





Fig. 1 2-1 0. A, It is preferable to maintain as much coro- 
nal tooth structure as possible, provided it is sound and of 
reasonable strength. B, Extensive caries has resulted in the 
loss of all coronal tooth structure. This is less desirable than 
the situation in A, because greater forces are transmitted to 
the root. 




Fig. 1 2-1 1 . Extending a preparation apically creates a 
ferrule and helps prevents fracture of an endodontically 
treated tooth during function. A, Prepared with a ferrule 
(arrows). B, Prepared without a ferrule. 



sistance of the restored tooth . The once common 
clinical practice of routine coronal reduction to the 
gingival level before post-and-core fabrication is 
outmoded and should be avoided (Fig. 12-10). Ex- 
tension of the axial wall of the crown apical to the 
missing tooth structure provides what is known as 
a. ferrule (Fig. 12-11) and is thought to help bind the 
remaining tooth structure together, preventing root 
fracture during function ^^ ^^ Although there is evi- 
dence that preserving as much coronal tooth struc- 
ture as possible will enhance prognosis, it is less 
clear whether the prognosis will improve by creat- 
ing a ferrule in an extensively damaged tooth by 
surgical crown-lengthening. In this latter circum- 
stance, although the crown-lengthening allows a 
ferrule, it also leads to a much less favorable crown- 
to-root ratio and therefore increased leverage on the 
root during function (Fig. 12-12). One recent labora- 
tory study showed that creating a ferrule through 



I 



Section 2 Clinical Procedures-Part I 






Fig. 1 2-1 2. Effect of apical preparation on crown-to-root ratio. A, Schematic of extensively damaged 
premolar tooth. Apical extension of the gingival margin would encroach on the biologic width (p. • • e), 
This preparation has no ferrule. B, Creating a ferrule with orthodontic extrusion (see Fig. 6-21) reduces 
root length (R) while crown length (C) remains unchanged. C, Surgical crown lengthening also reduces 
root length (R) but increases crown length (C). This results in a much less favorable crown-to-root ratio, 
which may not in fact strengthen the restoration. 

(Courtesy Dr A G Gesmff Fww. GegauffAG.J Dent ReS 78:223,1999 [abstract].) 



i2aor 




Tapered ParaPost Radix Ftexi-Post Kurei- 



Length 8 mm; Diameter 1.5-1.65 mm 
Cemented with zinc phosphate 

Fig. 1 2-1 3. Comparison of forces needed to remove dif- 
ferent prefabricated post systems. 

(Redrawn from Standlee JP, Caputo AA: J PrOSthet Dent 

68:436,1992.) 




Fig. 1 2-1 4. The use of a parallel- sided post in a tapered 
canal requires considerable enlargement of the post space, 
which can weaken the root significantly. 

(Courtesy Dr. R. Webber.) 



crown lengthening resulted in a weaker, rather than 
a stronger, restored tooth.'-' Creating a ferrule with 
orthodontic extrusion may be preferred as, al- 
though the root is effectively shortened, the crown 
is not lengthened (see Fig. 12-12, B). 

RETENTION FORM 

Anterior Teeth. Dislodgment of a post-retained 
anterior crown is frequently seen clinically and 
results from inadequate retention form of the pre- 
pared root. Post retention is affected by the prepara- 
tion geometry, post length, diameter, surface tex- 
ture, and by the luting agent. 

Preparation Geometry. Some canals, particu- 
larly in maxillary central incisors, have a nearly cir- 
cular cross section (see Table 12-3). These can be pre- 
pared with a twist drill or reamer to provide a 
cavity with parallel walls or minimal taper, allow- 
ing the use of a preformed post of corresponding 
size and configuration. Conversely, canals with el- 
liptical cross sections must be prepared with a re- 
stricted amount of taper (usually 6 to 8 degrees) to 
ensure adequate retention while eliminating unde- 
sired undercuts. This is analogous to an extracoro- 
nal preparation (see Chapter 7). With extracoronal 
preparations, retention increases rapidly as vertical 
wall taper is reduced (see Chapter 7). Although re- 
tention can be further increased by using a threaded 
post, which screws into dentin, this procedure is not 
recommended because of residual stress in the 
dentin. If the procedure is used, however, threaded 
posts must be "backed off" to ensure passivity; oth- 
erwise, the root will fracture. 

Laboratory testing has confirmed that parallel- 
sided posts are more retentive than tapered posts 
and that threaded posts are the most retentive (Fig. 
12-13). However, these comparisons are relevant 



Chapter 12 Restoration of the Endodonrically Treated Tooth 



I 



1000^ 

750- 

z 

£ 500- 
250" 



EMBEDMENT DEPTH 



D 
D 



5 mm 



8 mm 



JUk 




LJnift'k 
Uapered) 



VVbaledent 
(parallel) 



Kurer 

(threaded) 



DiamtJtG'r 1 .0 mm cemented with zinc phosphalU' 

Fig. 1 2-15. Effect of the depth of embedding a post on its retentive capacity. 

(Data from Standlee JP et al: J PrOSthet Dent 39:401, 1978.) 





Short posts are 
more likely to 
result in root 
fracture. 




Fig. 1 2-1 6. Faciolingual longitudinal sections through a maxillary central incisor. A, With a post of 
the correct length, a force (F) applied near the incisal edge of the crown will generate a resultant couple 
(R). B, When the post is too short, this couple will be greater (R'), leading to the increased possibility of 
root fracture. 



only if the post fits the root canal properly, because 
retention is proportional to the total surface area. 
Circular parallel post systems are only effective 
in the most apical portion of the post space because 
the majority of prepared post spaces demonstrate 
considerable flare in the occlusal half. Similarly, 
when the root canal is elliptical, a parallel- sided 
post will not be effective unless the canal is consid- 
erably enlarged, which would significantly weaken 
the root unnecessarily (Fig. 12-14). 

Post Length. Studies have shown that as 

post length increases, so does retention. However, 
the relationship is not necessarily linear (Fig. 12-15). 
A post that is too short will fail (Fig. 12-16), whereas 
one that is too long may damage the seal of the root 



canal fill or risk root perforation if the apical third is 
curved or tapered (Fig. 12-17). Absolute guidelines 
for optimal post length are difficult to define. Ideally, 
the post should be as long as possible without jeop- 
ardizing the apical seal or the strength or integrity of 
the remaining root structure. Most endodontic texts 
advocate maintaining a 5-mm apical seal. However, 
if a post is shorter than the coronal height of the clin- 
ical crown of the tooth, the prognosis is considered 
unfavorable, because stress is distributed over a 
smaller surface area, thereby increasing the proba- 
bility of radicular fracture. A short root and a 
tall clinical crown present the clinician with the 
dilemma of having to compromise the mechanics, 
the apical seal, or both. Under such circumstances, 
an apical seal of 3 mm is considered acceptable. 



I 



Section 2 Clinical Procedures-Part I 




Fig. 12-17. A, Correct post length. B, The post is too short; the consequences are inadequate reten- 
tion and increased risk of root fracture. C, The post is too long, jeopardizing the apical seal. 



Post Diameter. Increasing the post diameter in 
an attempt to increase retention is not recom- 
mended because it may unnecessarily weaken the 
remaining root. Although one group of investiga- 
tors reported that increasing the post diameter in- 
creased retention, other groups do not confirm 
this. Empirical evidence suggests that the overall 
prognosis is good when post diameter does not ex- 
ceed one third of the cross-sectional diameter of the 
root. 

Post Surface Texture. A serrated or roughened 
post is more retentive than a smooth one," and 
controlled grooving of the post and root canal (Fig. 
12-18) considerably increases the retention of a 
tapered post. 

Luting Agent. When considering traditional 
cements, the choice of luting agent seems to have Ut- 
ile effect on post retention or the fracture resis- 
tance of dentin. 34 However, adhesive resin luting 
agents (see Chapter 31) have the potential to im- 
prove the performance of post-and-core restora- 
tions; laboratory studies have shown improved re- 
tention. Resin cements may be indicated if a post 
becomes dislodged. Resin cements are affected by 
eugenol-containing root canal sealers, which should 



be removed by irrigation with ethanol or etching 
with 37% phosphoric acid if the adhesive is to be ef- 
fective. 37 Zinc phosphate and glass ionomer have 
similar retentive properties-polycarboxylate and 
composite resin have slightly less .38 Some resin and 
glass ionomer cements have demonstrated signifi- 
cantly higher retention in comparison to hybrid ce- 
ments. Although the choice of luting agent may 
become more important if the post has a poor fit 
within the canal, a post-and-core should be re- 
made if any rotation or wobble is present. 

Posterior Teeth (Fig. 12-19). Relatively long 
posts with a circular cross section provide good re- 
tention and support in anterior teeth but should be 
avoided in posterior teeth, which often have curved 
roots and elliptical or ribbon- shaped canals. For 
these teeth, retention is better provided by two or 
more relatively short posts in the divergent canals. 

When amalgam is used as the core material, it can 
be condensed either around cemented metal posts 
or directly into short, prepared post spaces. If more 
than 3 to 4 mm of coronal tooth structure remains, 
use of the root canals for retention is not necessary, 
and this avoids the chance of perforation. Using 
the canals for retention can provide good results ;z 
although the strength of the tooth once a complete 



Chapter 12 Restoration of the Endodontically Treated Tooth 



I 



600n 



400- 



200- 



_11 



Casl Cast Ca&t Cast Parallel 

tapered lapered tapered and tapered and sided 

(zinc (composite grooved (zinc grooved (compo- (Whaledent) 

phosphatej re:>in) phosphate) site resin) 



I 1 

NS(p<0.Q5} 

Fig . 12-18 . Effect of horizontal grooving on the retention of tapered posts. NS, Not significant. 

(Modified slightly from Wood WW: I Prosthet Dent 49:504,1983.) 




Fig . 12-19. When preparing posterior teeth for intra- 
coronal retention, the practitioner must be careful to avoid 
perforation, especially on the distal surface of mesial roots 
and the mesial surface of distal roots, where residual tooth 
structure is normally thinnest (arrozvs). 

crown has been provided is not dramatically influ- 
enced by differences in technique. 

Mandibular premolars and molars with a reason- 
able amount of remaining coronal tooth structure, 
when coupled with a circumferential cervical band 
of tooth structure with restricted taper of about 2 
mm, can often be restored with amalgam directly 
condensed into the chamber. Core buildups in mo- 
lars with one or more missing cusps will benefit 
from one or more cemented posts around which the 
amalgam can be condensed. The posts provide the 



additional retention, which was compromised be- 
cause of the missing tooth structure. In mandibular 
molars, the larger distal canal is recommended for 
post placement. In maxillary molars, the palatal 
canal is used (see Fig. 12-2, C and D). 

Although it is possible to restore a molar with 
three or more missing cusps with multiple posts 
and amalgam, the tooth's overall importance must 
be assessed. If retaining the tooth is critical, a cast 
core can be used (made in sections that have differ- 
ent paths of withdrawal) (Fig. 12-20). An alternative 
preparation method for a posterior tooth is selecting 
the canals that are widest (normally the palatal of 
maxillary molars and the distal of mandibular mo- 
lars) for the major post and then preparing short 
auxiliary post spaces in the other canals with the 
same path of withdrawal (Fig. 12-21). 



RESISTANCE FORM 



Stress Distribution. One of the functions of a 
post-and-core is to improve resistance to laterally 
directed forces by distributing them over as large an 
area as possible. However, excessive internal prepa- 
ration of the root weakens it, and the possibility of 
failure increases. The post design should distribute 
stresses as evenly as possible. The incidence of 
radicular fracture increases with the use of threaded 
posts, and threaded flexible posts do not appear to 
reduce stress concentrations during function. 



I 



Section 2 Clinical Procedures-Part I 



CO 




ig. - U. Cast cores for posterior teeth can be made in interlocking sections, with each section ha\ 
ing its own path of withdrawal. 



B 



Distal 




"■ " ■ Single-piece castings can be made by selecting the larger-diameter canal and extending a 

second post for a limited distance into the smaller canal. A, A maxillary first premolar. B, A maxillary 

molar. C, A mandibular first molar. D to F, Post-and-core provided for a maxillary first premolar by 
the indirect technique. 



Chapter 12 Restoration of the Endodontically Treated Tooth 



I 



The influence of post design on stress distribu- 
tion has been tested using photoelastic materi 
als, strain gauges,46 and finite element 

analysis . From these laboratory studies, the fol- 
lowing conclusions have been drawn: 

1. The greatest stress concentrations are found 
at the shoulder, particularly interproximally, 
and at the apex. Dentin should be conserved 
in these areas if possible. 

2. Stresses are reduced as post length increases. 

3. Parallel-sided posts may distribute stress 
more evenly than tapered posts, which may 
have a wedging effect. However, parallel 
posts generate high stresses at the apex. 

4. Sharp angles should be avoided because they 
produce high stresses during loading. 

5. High stress can be generated during inser- 
tion, particularly with smooth, parallel- sided 
posts that have no vent for cement escape. 

6. Threaded posts can produce high stress con- 
centrations during insertion and loading, but 
they have been shown to distribute stress 
evenly if the posts are backed off a half-turn 
and when the head contact area is of suffi- 
cient size 

7. The cement layer results in a more even stress 
distribution to the root with less stress con- 
centrations. 

Rotational Resistance (Fig. 12-22). It is impor- 
tant that a post with a circular cross section does not 
rotate during function. This should not present a 
problem in areas where sufficient coronal tooth 
structure remains, because rotation is usually pre- 
vented by a vertical coronal wall. In areas where 
coronal dentin has been completely lost, a small 
groove placed in the canal can serve as an antirota- 




@ 



Fig. 12-22. Rotational resistance in an extensively dam- 
aged tooth can be obtained by preparing a small groove in 
the root canal. This must be in the path of placement of the 
post-and-core. 



tional element. The groove is normally located 
where the root is bulkiest, usually on the lingual as- 
pect. Alternatively, rotation can be prevented by an 
auxiliary pin in the root face. Rotation of a threaded 
post can also be preventedas by preparing a small 
cavity (half in the post, half in the root) and con- 
densing amalgam into it after the post is cemented. 

PROCEDURES 

Tooth preparation for endodontically treated teeth 
can be considered a three-stage operation: 

1. Removal of the root canal filling material to 
the appropriate depth 

2. Enlargement of the canal 

3. Preparation of the coronal tooth structure 

REMOVAL OF THE ENDODONTIC FILLING MATERIAL 
The root canal system should first be completely ob- 
turated; space should then be made for a post, thus 
ensuring that lateral canals are sealed. A post cannot 
be placed if the canal is filled with a full-length sil- 
ver point, so these must be removed and the tooth 
retreated with gutta-percha. 

There are two commonly used methods to remove 
gutta-percha (Fig. 12-23): one uses a warmed en- 
dodontic plugger, and the other uses a rotary instru- 
ment, which is sometimes used in conjunction with 
chemical agents. Although it is more time consuming, 
the warmed endodontic plugger is preferred because 
it ehminates the possibility that the rotary instrument 
will inadvertently damage the dentin. If it is more con- 
venient, the gutta-percha can be removed with a 
warmed condenser immediately after obturation (al- 
though not with a rotary instrument). This will not 
disturb the apical seal ■^°^^^ This method offers the addi- 
tional advantage of allowing the operator to work in 
an area where the root canal anatomy is still familiar. 

1. Before removing gutta-percha, calculate the 
appropriate length of the post. It should be 
adequate for retention and resistance but not 
long enough to weaken the apical seal. As a 
guide, make the post length equal to the height 
of the anatomic crown (or two-thirds the length 
of the root), but leave 5 mm of apical gutta-per- 
cha On short teeth, it will not be possible to 
meet both these restrictions, and a compro- 
mise must be made. An absolute minimum of 
3 mm of apical fill is needed. If this cannot be 
achieved without having a very short post, 
the tooth's prognosis is seriously impaired. 

2. Avoid the apical 5 mm if possible. Curva- 
tures and lateral canals may be found in this 
segment. Average values for crown and root 
length are given in Table 12-1. If the working 
length of the root canal is known, the length 




Length i.s NHVER gained with 
end-cutting iwist drills! Instead, 
a safe tipped instrument such as 
a PeesoRcamer or Gates Glidden 
drill is used. The twist drill is 
only used lo p^irallel the walls 
of the post spflce. 




Fig. 12-23. Gutta-percha can be removed from the canal with a heated endodontic plugger (A and 
B), a non-end-cutting bur (C) (e.g., a Gates Glidden drill), or a ParaPost drill (D) (with a rubber stop to 
ensure accuracy of the preparation depth). 
(A and B courtesy Dr. D.A. Miller.) 



Maxillary Teeth 

Cenfrai incisor 

Lateral incisor 

Conine 

First premolar 

Second premolor 

First molar 



Second motor 



Mandibular Teeth 

Central incisor 

Lateral incisor 

Canine 

First premolar 

Second premolar 

First molar 

Second molar 

MF, Mesiofociol M, Mesicf 
DF, Distofociol D, Distol 
£, Lingual. 



hd Root tengthsTm: 

Mcjn 
*. ri'W n Length' 



10.8 ± 07 

97 ± 0.9 

10.2 ± 0.8 

8.6 - 0.8 
7.5 ± 0.6 
7 4 ± 0.5 



7.4 - 0.5 



9,1 ± 0,5 
9.4 ± 0.7 
10.9 ± 0.9 
87 ± 0.7 
7.8 ± 0.6 
7.4 ± 0.5 

73 i 0.5 



Mean 
R(K)t l.eniath' 



1 2.5 ± 1 .6 

13.1 ± 1.4 

\5.S±2A 

127 ± 17 

13.5 ± L4 

MP 1 2,5 ± 1 .2 

DF 12.0± 1.3 

L 13 2 5: 1.4 

MFr2.8± 1,5 

DF 12.0 ± 1.4 

L13,4± 1.3 



12.4 ± 1.4 
13.0 i 1.5 

14.3 i 1.4 

13.4 r 1.3 
13.6 ± 17 

M13.5± 1.3 
D13.4 ± 1.3 
M13,4± 1.2 
D13,3± 1.3 



Two Thirds 

Root Length 



Root Length 
(to 4 mm from apex) 



8.3 


8.5 


87 


9.1 


10.5 


11.8 


8.5 


87 


9,0 


9.5 


8.3 


B,5 


8.0 


8.0 


8.8 


92 


8.5 


8.8 


8.0 


8.0 


8.9 


9.4 


8.3 


8.4 


87 


9.0 


9.5 


10.3 


8.9 


9.4 


9.1 


9.6 


9.0 


9.5 


8.9 


9.4 



8.9 

8,9 



9.4 
9.3 



Data from Shillinghur^^ UTet ah Calif Dent Ai^iw j 10r43, 19s: 
*SD listed after mean length. 



Chapter 12 Restoration of the Endodontically Treated Tooth 



I 



of the post space can be easily determined. 
Therefore, the incisal or occlusal reference 
point must not be lost as a result of prema- 
ture removal of coronal tooth structure. 

3. To prevent aspiration of an endodontic in- 
strument, apply a rubber dam before prepar- 
ing the post space. 

4. Select an endodontic condenser large enough 
to hold heat well but not so large that it binds 
against the canal walls. 

5. Mark it at the appropriate length (normally 
endodontic working length minus 5 mm), 
heat it, and place it in the canal to soften the 
gutta-percha. 

6. If the gutta-percha is old and has lost its ther- 
moplasticity, use a rotary instrument, making 
sure that it follows the gutta-percha and 
does not engage dentin (this will cause a root 
perforation). For this reason, high-speed in- 
struments and conventional burs are con- 
traindicated. Special post preparation instru- 
ments are available (Fig. 12-24). Peeso-Reamers 
and Gates GHdden drills are often used for this 
purpose. These are considered "safe-tip" in- 
struments because they are not end-cutting 
burs. The friction generated between the fill 
and the tip of these burs softens the gutta- 
percha, allowing the rotary instrument to track 
the canal with reasonable predictability. One 
study comparing rotary instruments-2 con- 
cluded that the Gates GHdden drill conformed 
to the original canal more consistently than the 
ParaPost drill, which is an end-cutting instru- 
ment. The latter is a twist drill and should only 
be used to parallel the walls of the post space. 
Considerable heat can be generated when us- 
ing these rotary instruments, especially during 
the ParaPost preparation stage. 



NOTE: End-cutting instruments should never 
be used to gain length because root perforation will 
result! 

7. If using a rotary instrument, choose it to be 
slightly narrower than the canal. 

8. Make sure the instrument follows the center 
of the gutta-percha and does not cut dentin. 
Often, only a part of the root canal fill needs to 
be removed with a rotary instrument, and the 
remainder can be removed with the heated 
condenser. A rotary instrument should not be 
used immediately after obturation, because it 
may disturb the apical seal.-" 

9. When the gutta-percha has been removed to 
the appropriate depth, shape the canal as 
needed. 

This can be accomplished by using an endodon- 
tic hand instrument or a low- speed drill. This pro- 
cedure removes undercuts and prepares the canal to 
receive an appropriately sized post without exces- 
sively enlarging the canal. Files are a conservative 
approach to shaping the canal walls and permit si- 
multaneous removal of any small residual undercuts 
in the chamber. If a parallel-shaped post is desired, 
a low-speed twist drill set to the same length as the 
most recently used Peeso-Reamer can be used. 

The post should be no more than one third the 
diameter of the root,'" with the root and walls at 
least 1 mm thick. Obviously, when deciding on ap- 
propriate post diameters, a knowledge of average 
root dimensions is important. These have been cal- 
culated-6 and are presented in Table 12-2. Knowl- 
edge of root canal cross section also is significant in 
post selection. Prefabricated posts are circular in 
cross section, but many root canals are elliptical, 
which makes uniform reduction with a drill impos- 
sible. A summary of canal shapes is presented in 
Table 12-3. 




Fig. 12-24. Commonly used instruments for gutta-percha removal and canal enlargement. A, En- 
dodontic pluggers, two sizes of Peeso-Reamers with corresponding twist drills and endodontic file. Note 
attached floss as a safety precaution. B, The ParaPost twist drill corresponds in size to an aluminum post 
used to fabricate provisionals, a plastic post for patterns, and a stainless-steel or titanium post. 
(Courtesy Dr. J.A. Nelson.) 




Section 2 Clinical Procedures -Part I 



Average I^^^T) 


tnTTietefPHIB 




=if 
\n^ 


TABLE 12-2 J 










Diameter 

4 mm horn 


Recommended 




CE] 


FuRMtiont 


Midpoint 


Apex^ 


R)sl Diameter 


Maxillary Teeth | 


Central Incisor 


MD 6J ± 0,5 


— 


5.2 ± 0.5 


3-8 ± 0.4 


1-7 




FL 6.4 ± OA 


— 


5.8 ± 0.4 


4,3 ± 0.4 




Lateral inci^r 


MD 4.9 ± 0.5 


— 


4.0 ±0.5 


3-2 ± 0.5 


1.3 




FL 5.7 - 0,5 


— 


5.4 ± 0.5 


4.2 ± 0.4 




Conine 


MD 5.4 ± 0.5 


— 


4.4 ± 0.5 


3.3 ± 0.5 


1.5 




FL 77 ± 0.6 


— 


7.2 ± 0.6 


4.8 ± 0.6 




First premolar 


MD4.1 ± 03 


Fociol MD - 


3.6 ± 0.4 


2.6 - 0.4 


0.9 




FL 8 1 ± 07 


FL- 


3.4 ± 0.4 


2.4 ± 0.4 








Lingual MD — 


3.3 ± 0.3 


2.5 ± 0.4 


0.9 






Fl- 


3-3 ± 0.4 


2.4 - 0.5 




Second premolar 


MD 4,9 ± 0.3 


— 


3.8 ± 0.4 


3.2 ± 0.6 


1.1 j 




FL 7.9 ±0.5 


— 


7.0 ± 0.7 


5.0 ± 07 




First mdar 


MD 77 ± 0.4 


Mesio- MD 3.4 ± 0.3 


3.1 ± 0.3 


2.9 r 0.4 


1.1 




FL 10.5 ±0.5 


Fociol FL 6.8 ± 0.5 


5.8 ± 0.7 


4.8 ± 0.7 








Disto-MD3.1 ± 0.2 


2.8 ± 0.3 


2.6 ± 0.4 


1.1 






Facial FL 5.0 ± 0.4 


4.4 ± 0.5 


3.8 ± 0.5 








Ungual MD 57 ± 0.5 


5.0 ± 0.5 


4.4 ± 0.5 


1.3 






FL 4.3 ± 0-4 


37 - 0.4 


3.3 - 0.4 




Second molar 


MD7.3 ±0-4 


Mesio- MD 3-4 ± 0.3 


3.1 ± 0.3 


27 ± 0.4 


1.1 




FL10.4 ±0.6 


Facial FL 6.6 ± 0.5 


5.6 ± 07 


4-5 ± 0.7 








Disto- AAO 3.1 ± 0.4 


2-8 ± 0.3 


24 ± 0.4 


0.9 






Facial FL 4.3 ±0.4 


3.8 ± 0.4 


3.2 ± 0.4 


t 






Linguol MD 4.9 ± 0.5 


4.2 ± 0.5 


3.6 ± 0.5 


1.3 






FL 4.5 ± 0.4 


3.9 ± 0.4 


3-1 ± 0.4 




Mandibular Tefth 


Central incisor 


MD 3,3 t 0.3 


— 


27 ± 0.3 


2.1 ± 0.2 


0.7 




FL 5.5 ± 0,5 




5.6 ± 0.4 


4.3 ± 0.6 




Laterol inctsor 


MD 3,6 -: 0.3 


" 


2.7 ± 0.4 


2.0 i 0-2 


0.7 




FL 5,9 .1. 0.4 




57 ± 0.5 


4.3 ' 0.5 




Canine 


AAD 5.2 ± 0.6 


— 


4.0 ± 0.5 


3.2 ± 0.7 


1.5 




Fl 7.8 ± 0.8 




7.3 ± 0,6 


5.0 ± 0.5 




First premolar 


MD5J ± 0.4 


— 


4.0 ± 0.4 


3.2 ± 0.4 


1.3 




FL 6.6 T 0.4 




6.0 ± 0-5 


4.3 ,^ 0.5 




Second premolar 


MD 5.3 ± 0.3 


— 


4.3 ± 0.3 


3.5 ± 0.5 


1.3 




FL 7-0 ± 0.5 




6.0 ± 0.6 


4.4 ± 0.5 




First molar 


MD 8.9 ± 0.6 


Mesio- MD 3.7 ± 0-2 


3-2 ± 0-3 


2.8 - 0.3 


1.1 




FL 8,3 ± 0.6 


Facial FL 3.4 ± 0.3 


3.1 ± 0.3 


2.8 1 0,4 








Mesio' MD 3-4 ±0.3 


2.9 ± 0.3 


2.5 1 0.3 


0.9 






Ungual FL 3.5 ±0.4 


3.2 ± 0.3 


2.7 ± 0.4 








Distal MD 3-5 ± 0.4 


2.8 ± 0.4 


27 i 0.4 


1.1 






FL 7-6 ± 0.8 


6.6 ± 1.2 


5.4 • 0.8 




Second molar 


MD 9.3 ± 0.7 


Mesio' MD 3.6 ± 0.3 


3,1 ± 0.3 


2.6 ± 0.3 


0.9 




FL 8.3 ± 07 


Facial FL 3.2 ± 0.3 


2-8 ± 0.3 


2.4 ± 0.4 








Mesio- MD 3-6 ± 0.4 


3.0 ± 0.4 


2.5 ± 0.4 


0-9 






Lingual FL 3.2 ± 0.5 


2.8 ± 0.4 


2.3 i 0.4 








Distal MD 4.1 ± 0.4 


3.5 ± 0.4 


3.0 ± 0-4 


1.1 






FL 6-8 ± 0.8 


5.9 ± 0.9 


4-7 - 07 




' ' ' ' - 1 



Data /mm Shillingburg HT et .il: Calif Dnit /^.^iSftc } 10:43, 19S2. 
*N = 5t) for each tooth. 

tFuajtion ciistincf from tlie CEJ: maxillary first molar, 4. 1 mm; maxiliaiy second molar, 3.2 mm; mandibular first molar, 3.1 mm; mandibu- 
lar second molar, 3.3 mm. 
tBccau^' of greater moot length, the mean distance from the apex on maxillary canine measurements is 5.1 mm. 



Chapter 12 Restoration of the RnHnrln ntTrnlly TrenteH Tooth 



I 



ENLARGEMENT OF THE CANAL 

Before enlargement of the canal, the type of post 
system to be used for fabrication of the post-and- 
core must be chosen. 



The advantages and disadvantages of different 
post types are summarized in Table 12-4. Because 
no system has universal application, being familiar 
with more than one technique is a significant 



TABIE 12-3 



Elliptical 



Circular 



Moxillary central incisor 



Maxillary fi^s^ premolar (two roots} 

Mandibular second premoiar 
Maxillory molars [distobuccal roo^s) 



Buccolineual 



Maxillary lateral incisor 

Maxillary canine 

Mandibular incisors 

Mandibulcir canine 

Moxillary first premolar (single root) 

Mondibular first premolar 

Maxiilary second premolar 

Maxillary molors (mesiobuccal roots) 

Mandibular molars [meslo! and distal roots) 



IVIesiodistal 



Maxillary molars (palatal roots) 



IVoai VVeine FS; Endodonfic tlierapit, ed 4, St (.Aiiiis, T-W9, Mtisby, pp 225-26*-^. 



Aya t l ihJ^Mgps frriandT Cia Te Systems 



Amalgam 

Glass 
iofiOTTier 

Compos ife 
resin 

Custom cast 

post-and- 

core 
Wire post 

and cast 

core 
Tapered 

prefabricated 

post 
Parallel-sided 

prefabricated 

post 



Advarttasfis 



Conservative of tooth 

shructure 
Stroightforv.'ard technique 
Conservative of tooth 

structure 
Straightforv/ard technique 
Con servo Hve of tooth 

structure 
Straightforward technique 
High strength 
Better fit rhan 

prefabricated 
High strength 
High stiffness 

Conservotive of tooth 

structure 
High strength ond stiffness 
High strength 
Good retention 
Comprehensive system 



Threoded post High retention 



Carbon fiber 
post 

Zircon Id cerd- 
mic posts 

Woven fiber 
posts 



Dentin bonding 
Easy removal 



Esthetics 
High stiffness 
Esthetics 
Dentin bonding 



DisndvaTiitageti 



Low tensile strength 
Corrosion with bose metal 

Difficult condensation 
Low strength 

Low strength 

Continued polymerization 

Microleakage 

Less stiff than wrought 

Time consuming, complex 

procedure 
Corrosion of base metal 
Pt-Au-Pd wire expensive 

Less retentive than parallel- 
sided or threaded systems 

Precious metal post expensive 
Corrosion of stainless-steel 
Less conservative of tooth 

structure 
Stresses generated in canol 

may lead to fracture 
Not conservative of coronal 

and radicular tooth structure 
Low strength 
Microleakage 
Black color 

Urieeffattt citmcal pSrferilfitirite 

Low strength 

Uncertain clinical performance 



Kecommended Use Precautions 



Molars with adequate 

coronal tooth 

structure 
Teeth with minimum 

tooth structure 

missing 
Teeth with minimum 

tooth structure 

missing 
Elliptical or flared 

canals 

Small circulor canols 



Small arcu\ar canals 



Small 



circular canals 



Only when maximum 
retention is 
essentia) 

Minimal missing 
tooth structure 

Uncertain endodontic 
prognosis 

High esthetic demand 

High esthetic demand 



Not recommended in 
teeth under lateral 
load (onteriors) 

Not recommended in 
teeth under lateral 
lood 

Not recommended in 
teeth under lateral 
load 

Core to remove nod- 
ules before try- in 

Care to avoid perfo- 
ration during 
preparation 

Not recommended for 
excessively flared 
canals 

Care during 
preparation 



Care to avoid fracture 
during seating 



Not recommended for 
teeth under lateral 
load 



Not recommended for 
teeth under lateral 

load 



I 



Section 2 Clinical Procedures-Part I 



advantage. A wide range of prefabricated posts are 
available. They come in many shapes and sizes 
(Table 12-5 and Figs. 12-25 and 12-26). The diame- 
ters of nine popular prefabricated posts are given in 
Table 12-6. Parallel- sided prefabricated posts are 
recommended for conservatively prepared root 



canals in teeth with roots of circular cross section. 
Excessively flared canals (e.g., those found in young 
persons or in individuals after retreatment of an en- 
dodontic failure) are most effectively managed with 
a custom post. However, situations should be eval- 
uated on an individual basis. 

Text continued on p. 297 



■wr 

? « 

Fig. 1 2-25. Classification of prefabricated posts. A, Tapered, smooth- sided posts. B, Tapered, serrated 
posts. C, Tapered, threaded posts. D, Parallel, smooth-sided posts. E, Parallel, serrated posts. F, Parallel, 
threaded posts. 

(Redrawn from Shillingburg HT, KesslerJC: Restoration of the endodontically treated tooth, Chicago, 1982, 
Quintessence Publishing. ) 




I \ Ml 




Fig. 1 2-26. Radiographs of the six categories of endodontic posts. A, KG Endowel, tapered and 
smooth sided. B, Unimetric, tapered and serrated. C, Dentatus, tapered and threaded. D, CTH Beta, 
parallel sided and smooth. E, ParaPost (two sizes), parallel sided and serrated. F, Flexi-Post (in the right 
maxillary first molar), parallel sided and threaded (note the split shank). 

(A courtesy Dr. D.A. Miller and Dr. H.W. Zuckerman; B courtesy Dr. LA. Roseman; C courtesy Dr. FS. Weine 
and Dr. S. Strauss; D courtesy Dr. J.F. Tardera; E courtesy Dr. J.L. Wingo; F courtesy Dr. L.R. Farsakian.) 



Shank 







Product (Vendor) 



Tapered Smooth Posts 

C-l Post (Parkell Products) 
ER Casting Post (Brosseier USA) 
^ ER Cerapos* (Brosseler USA) 

ER Post System (Brasseler USA) 
ER PCR Post (Brasseler USA) 
Cytco (Dentsply Ma! liefer) 

— Filpost (Fllhol Dental USA) 

— Plastic Impression Pin (Union Broach) 
Colorama (Metal or Dentol USA) 

^ Endodontic Post (Sterngold) 

Luscent Anchors (Dentotus USA) 

^■^ Stress- Free Post (Denovo) 
Endowd (Star Dental) 
UM C-POST (Bisco) 
PD Sprues (R Chige) 
Tapered Serrated Posts 
Unimetric (Dentsply Maillefer) 
PD Solid & Hollow Posf (R Chige) 



PB.SS 
PB 

Ti alloy 

Ti alloy 

Ti alloy 

Ti 

PB 

PB 

PB 

Fiberglass-resin 

SS 

PB 

Carbon fiber- res in 

PB, SS 

Ti olloy 
SS 



Ch^ir-ictfri sties 



Flat tip 

Flat tip 

Blunt tip 

Btunttip 

Blunt tip 

Blunt tip, 3 coronal threads 

Blunt Hp 

Blunt tip 

Blunt tip 

Blunt tip 

Blunt tip 

Blunt tip, ISO sizes: 50 to 130 

Poinled Hp, JSO^ sizes: 80 to 140 

Pointed ttp, JSOii sizes: 100, 1 20, UO 

Pointed tip 

Knurled 
Knurled 



Diameter (mm)t^ 



1.3 & 1.6 

1,1 to 1.7 
LI to 1.7 
1.1 to 1.7 
1.1 to 17 
0.9 & 1.2 

1.3 & 1.6 

1.4 & 1.7 
1.3 to 2,0 
1.7 & L8 

1.1 to 1,6 
0.7 to 1 .5 

1 .0 to 1 .6 

1 .2 to 1 .6 

1.1 to 2.1 

1 .6 to 1 .8 
1.1 to 2.1 



*Posls are categorized by their radioj^raphic silhuuL-tte from the apical S mm of the shank 

t Posts a re not pho lograp hed to sea I e. 

|Composition key: An, Cold; Bmss. alloy ot copper and ?inc (brass post'j are ,£;old plated); Carbon fibers hound by epoxy-resin matrix; Cn. copper; Ni, nickel; PB, plastic bumotit; Pd, palladium; 

£5, stainless stecf; Tf, titanium (Jf indicatesi approximately 99% pure titanium, Ti alh-ii/ indicates a content of approximately 90"%, titanium); Zri)., zirconium dioxide. 

§Shank diameter includes the threadii of relevant posts; diameters of tapered posts are taken 8 mm from the ap!c<il tip. 

HSO indicates that the post corresponds to standardized file sizes (set by the International Standards Organization). 



Continued 



Shank 



yuywu 






Product ('Vendor) 



Tapered Serrated f osts — confd 

Nu&ond {Ellman Internofional) 
Davis Crown Post (Union Brooch} 
^=^ Lumfrtex (Derttatus USA) 
Tapered Threaded Posre 
AncoreK (E C Moore) 
Ancorextro (E C Moore) 
Dentatus Classic Post {Dentabs USA} 
Topered Obturation Post (Union Broach) 
Ventro-Post (Ellman International) 
Parallel-Sided Smooth Posts 



yM 



|>4«- 



BBri^"^F 



a » ■ " C-Post (Bisco} 

^ Aest}ieti'Post (Bisco) 

IntegroPost System (Prefnier} 
CTH Beta Post (aH) 



)M 



(SiSi 



■-* CTH R Series (CTH) 

ProPost (Dentspl/ Tufsa Dental) 

Vorio Cast Passive Post (Broiseler USA) 

PARALLlL-SlOED SERRATED FOSTS 

ParaPost (Coltene/Whaledefit} 
PoroPost XP (Coltene/Whaledent) 
Unity (CoJtene/Wholedent) 



ss 
ss 

PB 

Ti 

■R 

Tij SS, Brass 

SS 

SS 

Corbon Bber- resin 
Carbon fiber-resin 
Ti alloy 
SS 

ss 
ss 



Ti alloy, PB, SS 
Tt alloy, PB, SS 
Ti aiby, PB 



C haractiTislics 



Knurled 

'Deeply grooved 
Deeply grooved 

Tightly threaded 
Tightly threaded 
Tightly threaded 
Tightly threoded 
Sparsely threaded 



Dual size shank, teipered apical end 
Dual size shank, tapered apical end 
Vertiool serrations, flat Up 
Vertical grooves, flat tip 
Vertical grooves, flat tip 
Smooth, topered opicol end 
Smooth, blunt Hp 

Fine serrations, flat tip 
Diamond- shaped grooves, flat tip 
Diamond'shaped grooves, flat tip 



t<:'T*:-j'vj.-r 



Diamt'ttT {mmjv? 


0.9 to 2.0 


1 .8 to 2.0 


).l to 1.8 


1.1 to 1.8 


1.1 to 1.8 


1.1 to 1.8 



1.2 to 1.6 

L4 

1.4 to 2.1 
1.4 to 2.1 
0.9 to 1 .5 
1.1 to 1.6 
IJ to 1.6 
0.8 to 1 A 
L2toK6 

0.9 to 1.8 
0.9 to 1 .8 
0.9 to 1.8 



liM^rm&^n^^iTi 



Product (Vendor) 



iB'jm^^s^TmMiik 



Shank 



|^.!W!H?-^-» 




tfcr 






L 



r<if^hnKWrifiM:«>' 



ParoPost XH {Colt^ne/Whaledent) 

ParoPost Plus (Coltene/Whaledent) 

FibreKor Post System (Jeneric/Pentron) 

ExactaCast (Essential Dental Systems} 

Vario Passive Post (Brasseier USA) 

Vario PCR Passive Post (Brasseler USA) 

Vbck Possive Post (Brassefer USA] 

Micropost (Donville Engineering) 

SB Post (J Morita USA) 

Versadov^el-A Series (Western Dental) 

Versadov/el-M Series (Western Dental) 

Versadowel-U Series {Western Dental) 

AccessPost (Essential Dental Systems) 

AccessPost Overdenture (Essential Dental Systems) 

ERA Direct Overdenture (Sterngold) 

PakaixeL'Sided Threaded Posts 

Compo-Post (Henry Schein) 

Golden Screw Post (EC Moore) 

Titanium Screw Post (EC Moore) 

Boston Post (Roy dent Dental Products) 

obturation Post (Union Broach) 



Composition t 



Ti alloy 

Ti alloy, SS 

Glass Fiber-resin 

PB 

Ti allay 

TI alloy 

TI alloy 

Ti alloy 

SS 

SS 

SS 

SS 

SS 

SS 

SS 

Brass 

Brass 

Ti 

Ti 

SS 



Characteristics 



Diomond-shaped-grooves, flat tip 
Serrated [edges, flat tip 
Serrated ledges, flat tip 
Wide grooves, flat tip 

Wide grooves, flat tip „ 

Wide grooves, flat tip 
Wide grooves, flat tip 
Fine grooves, flat tip 
Fine grooves, tapered tip 
Fine grooves, tapered tip 
Fine grooves, tapered tip 
Fine grooves, tapered tip 
Spiraling groove, fiat tip 
Spiraling groove, flat tip 
Fine serrations, flat tip 

Hgfitly threaded, pointed tip 
Tightly tlireaded, pointed tip 
Tightly threaded, pointed tip 
Tightly threaded, pointed tip 
Ttghtly threaded, pointed tip 



TABLE 12-5 



Diameter (mm) 



0.9 to 1.8 
0.9 to 1.8 

1.0 to 1.5 
0.7 to 1 .5 
1.21d1.6 
1.2 to 1,6 
1.2 to 1.6 
0.8toK6 
0.8 to 1 .6 
0.8 to 1.3 
0.8 to 1.3 
0.8 to 1.3 
0.8 to 1-6 

1.1 to 1 .6 
1.4 & 1.7 

1.1 to 1.8 
1,1 to 1.8 
1.1 to L8 
1.0 to 1.6 
1.3 

Continued 



Curre 



I \iLimpiet 



Shank 



Sc«Sv!viv^Iii3II3KS?fiffll' 






Product (Vendor) 



Pajrallel-Sided Threaded Posts — conf d 

K4 Ready Core Anchor (Teledyne Water RkJ SS 

K4 Universal Anchor (Teledyrie Water Pile) SS 

K4 Custom Core Anchor [Teledyne Water Pik) SS 

K4 DenKire Anchor (Teledyne Water PikJ SS 

Sure-Grip [R Chige) SS 

Vlock Active Post [Brasseler USA) Ti oiloy 

Vario Adive Post (&rossder USA) Ti oIloy 

Vario EiO Active Post (Brasseler USA) Ti alloy 

Radix- An kor (Dentsply Maillefer) Ti oIloy 

ParaPost XT (Coltene/Whaledent) Ti alloy 

Flexi'Post (Essential Dental S/items) T! alloy, SS 

Flexi-Flonge (Essentio! Dental Systems) Ti oIloy, SS 

Flexi-Overdenfure (Essenttol Dental Systems) Ti alloy, SS 



Ch.irAL'teristics 



Tightly threaded, flat tip 
Tightly threaded, flot tip 
Tightly threaded, flat tip 
Tightly threaded, flat tip 
Sparsely threaded, blurtt tip 
Sporsely threaded, blunt tip 
Sparsely threaded, blun» tip 
Sparsely threaded, flat tip 
Sparsely threaded, flot tip 
Sporsely threaded, grooves, fiat tip 
Sparsely threaded, split shank 
Sparsely threaded, split shank 
Sporsely threaded, split shank 



T?!<i meter (mm)' 



1 .6 to ZO 
1.5 to 2.0 

1 .7 to 2.0 

1 .8 to 2.0 
0.9 to 1.9 
K3tol.8 
1.3 to 1.8 

1.3 to 1.8 
1.2 to 1.6 
0.9 to 1,5 

1.0 to 1-9 

1.1 toL9 

1.4 to 1.9 



Chapter 12 Restoration of the Endodontically Treated Tooth 



I 

















MMmmxn. 










TABLE 12-6 J 


Post 0.80 0.90 0.95 


1,00 1,05 1.15 


1,20 1.25 1.35 


L40 


1,45 


1.50 1.60 1.65 1.75 


1.80 1,85 1,90 2.00 


Boston* 




X 


X 




X 
X 












X 










Dentahjs* 




X 






X 




X 
X 

X 


X 


X 


X 
X X 


Flexi'Posr 

Stress-free post size 70 + 

Ky Universol Anchor 

ParaPost 

Radix* 

Viock Possive Post 


X 




X 










X 








+ 


X 




























X 




X 


X 






X 








X 












X 
X 






X 








X 


X 












X 








X 





















'•Diiimutijr includos threads. 
+5 mm from tip. 
^10 mm from tip. 



B 





Fig. iz-z / . Enlargement of the root canal for a prefabricated post. 



Prefabricated Posts (Fig. 12-27) 

1. Enlarge the canal one or two sizes with a drill, 
endodontic file, or reamer that matches the 
configuration of the post (see Fig. 12-27, A and 
B). When using rotary instruments, alternate 
between the Peeso-Reamers and twist drills 
that correspond in size. In the case of a 
threaded post, the appropriate drill is fol- 
lowed by a tap that prethreads the internal 
wall of the post space. Parallel- sided posts are 
more retentive and distribute stresses better 
than tapered posts, but they do not conform 
well to the shape of a canal that has been 
flared to facilitate condensation of gutta-per- 
cha. In this situation, it may not be possible to 
enlarge the canal sufficiently to provide ade- 
quate retention for the post; in that case, a ta- 
pered custom-made post is preferred. 

2. Use a prefabricated post (see Fig. 12-27, C) 
that matches standard endodontic instru- 



ments. A tapered post will conform better to 
the canal than a parallel- sided post and re- 
quires less removal of dentin to achieve an 
adequate fit. However, it will be slightly less 
retentive and will cause greater stress con- 
centrations, although retention may be im- 
proved by controlled grooving. !!i 
3. Be especially careful not to remove more 
dentin at the apical extent of the post space 
than is necessary (see Figs. 12-14 and 12-27). 
NOTE: If careful measurement techniques have 
been followed, radiographs are not normally re- 
quired to verify the post space preparation. 

Most of the time a preformed parallel- sided post 
will fit only in the most apical portion of the canal. 
Modified posts are available with tapered ends, and 
these conform better to the shape of the canal 
although they have slightly less retention than par- 
allel-sided posts do, particularly the shorter ones. 
In the absence of a vertical stop on sound tooth 




Section 2 Clinical Procedures-Part I 



structure, such posts can also create an undesirable 
wedging effect. 

Custom-made Posts (Fig. 12-28) 

1. Use custom-made posts in canals that have a 
noncircular cross section or extreme taper. 
Enlarging canals to conform to a preformed 
post may lead to perforation. Often very Uttle 
preparation will be needed for a custom- 
made post. However, undercuts within the 
canal must be removed, and some additional 
shaping usually is necessary. 

2. Be most careful on molars to avoid root 
perforation. In mandibular molars the distal 
wall of the mesial root is particularly suscep 
tible. In maxillary molars the curvature of the 
mesiobuccal root makes mesial or distal per- 
foration more likely (Fig. 12-29). 

PREPARATION OF THE CORONAL TOOTH STRUCTURE 

After the post space has been prepared, the coronal 
tooth structure is reduced for the extracoronal 




Fig. 1 2-28. Custom-made posts are indicated for teeth 
with root canals whose cross section is not circular or is ex- 
tremely tapered. Further enlargement of the root canal is of- 
ten not necessary on these teeth. 




Fig. 1 2-29. Distal root curvature contributed to this 
mesial perforation (arrow) of a mandibular molar and ne- 
cessitated removal of the distal root segment. 

(Courtesy Dr. J. Davila.) 



restoration. Anterior teeth requiring a post-and-core 
are most effectively restored with a metal-ceramic 
crown (see Chapters 9 and 24). 

1. Ignore any missing tooth structure (from pre- 
vious restorative procedures, caries, fracture, 
or endodontic access) and prepare the re 
maining tooth as though it were undamaged 
(i.e., if a porcelain labial margin restoration is 
planned, a facial shoulder and lingual cham- 
fer are placed). 

2. Be sure that the facial structure of the tooth is 
adequately reduced for good esthetics. 

3. Remove all internal and external undercuts 
that will prevent withdrawal of the pattern. 

4. Remove any unsupported tooth structure, 
but preserve as much of the crown as possi- 
ble. Because tooth structure has been re- 
moved internally and externally, the remain- 
ing walls often are thin and weakened. 
Defining absolute measurements for the di- 
mensions of the residual coronal walls is dif- 
ficult, but ideally they should be at least 
1 mm wide. Wall height is reduced proportion- 
ally to the remaining wall thickness because 
tall, thin walls have a tendency to fracture 
when the provisional restoration is removed 
and during try-in and seating of the casting. 

5. In addition, be sure that part of the remaining 
coronal tissue is prepared perpendicular to 
the post (see step 4 in Fig. 12-8), because this 
will create a positive stop to prevent over- 
seating and splitting of the tooth. Similarly, 
rotation of the post must be prevented by 
preparing a flat surface parallel to the post 
(see step 5 in Fig. 12-8). If insufficient tooth 
structure for this feature remains, an anti- 
rotation groove should be placed in the canal 
(see Fig. 12-22). 

6. Complete the preparation by eliminating 
sharp angles and establishing a smooth finish 
line. 

POST FABRICATION 

Prefabricated Posts. Technique simplicity is 
one advantage of using prefabricated posts. A post is 
selected to match the dimensions of the canal, and 
only minimum adjustment is needed for seating it to 
the full depth of the post space. The coronal half of 
the post may have an inadequate fit because the root 
canal has been flared. This can be corrected by 
adding material when the core is made. 

Available Materials (see Table 12-5). Prefabri- 
cated parallel- sided posts are made of platinum- 
gold-palladium (Pt-Au-Pd or PGP), nickel- chromium 



Chapter 12 Restoration of the Endodontically Treated Tooth 



I 



(Ni-Cr), cobalt-chromium (Co-Cr), or stainless steel 
clasp wire. Serrated posts come in stainless steel, 
titanium, or nonoxidizing noble alloy. Tapered 
posts are available in Au-Pt, Ni-Cr, and titanium al- 
loys. All these posts have a high modulus of elastic- 
ity and an elongated grain structure, which con- 
tribute to their more suitable physical properties as 
compared to cast posts. Essentially, they are more 
rigid. 

Failure of posts cast in Type III gold when loaded 
at a 45-degree angle has been attributed to bend- 
ing. Although posts cast in stiffer (Type IV) gold or 
Ni-Cr alloys can be expected to resist bending bet- 
ter, prefabricated posts should possess even more 
desirable physical properties, although their prop- 
erties can deteriorate when a core is cast to a 
wrought post ^'^ 

Carbon-fiber posts have increased in popularity 
during recent years.* These posts consist of bundles 
of stretched aligned carbon fibers embedded in an 
epoxy matrix. The resulting post is strong but has 
significantly lower stiffness and strength when 
compared to ceramic and metal posts.'" Preliminary 
retrospective study of this system appears promis- 
ing" (Fig 12-30). However, a laboratory study com- 
paring teeth restored with carbon fiber posts and 
composite-resin foundations and teeth restored 
with custom post-and-cores cast in Type III alloy 
showed significantly higher fracture thresholds for 
the cast post-and-cores . 62 One advantage of a carbon 
fiber post is the ease of its removal for retreatment. 
The preferred technique involves drilling apically. 
The very strong carbon fibers prevent the drill from 
tracking laterally, avoiding penetration of the 
dentin. Therefore, if concern exists about the long- 
term prognosis of an endodontically treated tooth, a 
carbon fiber post should be considered. The chief 
disadvantage of a carbon fiber post is its black ap- 
pearance, which presents an esthetic problem (as 
can metal posts). 

Manufacturers have developed high- strength ce- 
ramic (zirconia) postst (Fig. 12-31) and ceramic 
composites (Fig 12-32) and woven fiber (e.g., poly- 
ethylene) posts, § all of which have excellent esthetic 
properties (see also Chapters 25 and 27). Ceramic is 
very strong and rigid; woven fiber is less strong and 
more flexible . 65 Because the systems are relatively 
new, judging how well the foundations will per- 



*C-Posts, Bisco: Chicago. 

tCosmoPost, Ivoclar: Amhurst, N.Y. 

^ij^stheti-Post, Bisco: Chicago. 

gFibreKor, Jeneric/Pentron Inc.: Wallingford, Conn, 

Luscent Anchor, Dentatusr New York. 



form in clinical practice is difficult, but they should 
be considered where esthetic demands are high. 

Corrosion Resistance. Several reports 68 
have linked root fracture to corrosion of base metal 
prefabricated post-and-core systems. One study, 
reporting on 468 teeth with vertical or oblique root 
fracture, attributed 72% of these failures to elec- 
trolytic action of dissimilar metals used for the post 
and the core (reaction occurring between tin in the 
amalgam core and stainless steel, German silver, or 
brass in the post). The authors suggested that vol- 
ume changes produced by corrosion products split 
the root. Although possible fracture mechanisms 
have been suggested . these studies are confusing 
cause with effect: The corrosion may have occurred 
subsequent to root fracture rather than causing it. 

Further study is needed to answer the question 
conclusively. However, in the meantime, avoiding 
the use of potentially corrodible dissimilar metals 
for post, core, and crown is recommended. 

Custom-made Posts. A custom-made post can 
be cast from a direct pattern fabricated in the pa- 
tient's mouth, or an indirect pattern can be fabri- 
cated in the dental laboratory. A direct technique 
using autopolymerizing or light-polymerized resin 
is recommended for single canals, whereas an indi- 
rect procedure is more appropriate for multiple 
canals. 

Direct Procedure 

1. Lightly lubricate the canal and notch a loose- 
fitting plastic dowel (Fig. 12-33, A). It should 
extend to the full depth of the prepared canal. 

2. Use the bead-brush technique (Fig. 12-33, B) 
to add resin to the dowel (Fig. 12-33, C) and 
seat it in the prepared canal. This should be 
done in two steps: Add resin only to the canal 
orifice first. An alternative is to mix some 
resin and roll it into a thin cylinder. This is in- 
troduced into the canal and pushed to place 
with the monomer-moistened plastic dowel. 

3. Do not allow the resin to harden fully within 
the canal. Loosen and reseat it several times 
while it is still rubbery. 

4. Once the resin has polymerized, remove the 
pattern (Fig. 12-33, D). 

5. Form the apical part of the post by adding 
additional resin and reseating and removing 
the post, taking care not to lock it in the canal. 

6. Identify any undercuts that can be trimmed 
away carefully with a scalpel. 

The post pattern is complete when it can be in- 
serted and removed easily without binding in the 



I 



Section 2 Clinical Procedures-Part I 





H 



Fig. 12-30. Carbon fiber posts. A, The C-Post system is available in various sizes and configurations. 
B, Gutta-percha is removed with hot instruments or a Gates Glidden drill. The canal is prepared sequen- 
tially with the drills provided by the manufacturer. C, The post is seated in the canal and shortened with a 
diamond rotary instrument or disk. Wire cutters should never be used to cut carbon fiber composites, be- 
cause they crush and weaken the composite structure. D, The canal is prepared by etching and priming ac- 
cording to the manufacturer's recommendations. The n the post is prepared by airborne particle abrasion. 
E, The luting resin is introduced into the canal with a lentulo spiral. F, The post is seated and the core built 
up with the recommended core resin. G, The preparation is finalized. H, The completed restoration. 
(Courtesy Bisco, Inc.) 



Chapter 12 Restoration of the Endodontically Treated Tooth 



I 





Fig. 1 2-31 . A, Zirconia posts, such as the CosmoPost, shown with the corresponding rotary instru- 
ments, are esthetic and strong. B, Special pressable ceramics are available to form the core (composite 
resin can also be used). (See also Fig. 25-19.) 

(Courtesy Ivoclar North America.) 




Fig. 1 2-32. Ceramic composite post. A, The -/Estheti-plus post system uses ceramic fibers in a resin 
matrix. B, Cross-sectional and C, longitudinal sections of the fiber composite. 
(A courh'sy Bisco, Inc.; B smd C coar test/ Dr. J. Wan^.) 





Fig. 1 2-33. Fabrication of an acryUc resin pattern for a custom-made post. 

(Courtesy Dr. R. Webber) 



I 



Section 2 Clinical Procedures-Part I 



canal. Once the pattern has been made, additional 
resin or light-polymerized resin* is added for the 

core. 

Pattern Fabrication with Thermoplastic 
Post (Fig. 12-34) 

1. Fit the plastic rod to the prepared post space. 
Trim the rod until the bevel area is approxi- 
mately 1.5 to 2 mm occlusal to the finish line 
for the core. 

2. Lubricate the canal with a periodontal probe 
and petroleum jelly. 



3. Heat the thermoplastic resin over a flame un- 
til the material turns clear or heat the resin in 
a low-temperature glue gunt. 

4. Apply a small amount of the heated resin 
to the apical end of the rod to cover two 
thirds of the anticipated length of the post 
pattern. 

5. Fully insert the rod into the prepared post 
space. Lift after 5 to 10 seconds and reseat. In- 
spect the post pattern for completeness and 
remove any projections that result from un- 
dercuts in the canal with a scalpel blade. 



*LX Gel, Dentatus: New York; Palavit G LC, Heraeus 
Kulzer, Inc.: South Bend, Indiana. 



+TherTn.ogrip, Black £ind Decker, htc: Hunt Vdlley, Md. 




Fig. 12-34. The Merritt EZ Cast Post system. A, The canal is lubricated and excess lubricant removed 
with paper points. The post was previously trimmed until its beveled portion protrudes about 1.5 to 2 
mm above the tooth preparation. B, A stick of the thermoplastic material is heated. C, The plastic rod is 
covered for about two thirds of the anticipated post length. D, The coated post is inserted and can be re- 
moved in 5 to 10 seconds. E, After any protrusions have been removed, the core is built from autopoly- 
merizing resin and trimmed to ideal tooth preparation form. F, The completed custom post-and-core. 
(From Rosenstiel SF et al: J Prosthet Dent 77:209, 1997.) 



Chapter 12 Restoration of the Endodontically Treated Tooth 



I 



6. For the direct technique, fabricate the core 
with conventional autopolymerizing resin 
using the brush-bead technique or syringe 
a light polymerized pattern resin (an easier 
technique). 

7. If the indirect technique is preferred, pick up 
the pattern with an elastomeric impression 
material, which can be poured in the conven 
tional manner. Soak the cast in warm water to 
help release the pattern. Reseat the post pat- 
tern and wax the core. 

8. Invest and cast the post-and-core. Phosphate- 
bonded investment is recommended because 
of its higher strength. 

Indirect Procedure (Fig. 12-35). Any elas- 
tomeric material will make an accurate impression 
of the root canal if a wire reinforcement is placed to 
prevent distortion. 

1. Cut pieces of orthodontic wire to length and 
shape them hke the letter J (Fig. 12-35, A). 

2. Verify the fit of the wire in each canal. It 
should fit loosely and extend to the full depth 



of the post space. If the fit is too tight, the im- 
pression material will strip away from the 
wire when the impression is removed. 

3. Coat the wire with tray adhesive. If subgingi- 
val margins are present, tissue displacement 
may be helpful. Lubricate the canals to facili 
tate removal of the impression without dis- 
tortion (die lubricant is suitable). 

4. Using a lentulo spiral, fill the canals with 
elastomeric impression material. Before 
loading the impression syringe, verify that 
the lentulo will spiral material in an apical 
direction (clockwise). Pick up a small 
amount of material with the largest lentulo 
spiral that fits into the post space. Insert the 
lentulo with the handpiece set at low rota- 
tional speed to slowly carry material into the 
apical portion of the post space. Then in- 
crease handpiece speed and slowly with- 
draw the lentulo from the post space. This 
technique prevents the impression material 
from being dragged out. Repeat until the 
post space is filled. 



All of the elastomeric 
impression materials 
require some form of 
reiniorcement when 
making a post space 
impression. 




Impression 
material 

Impression 
tray 

Wire 
reinforcement 



Fig. 12-35. Indirect procedure for post-and-cores. 



I 



Section 2 Clinical Procedures-Part I 



5. 



6. 



Seat the wire reinforcement to the full depth 
of each post space, syringe in more impres- 
sion material around the prepared teeth, and 
insert the impression tray (see Fig. 12-35, B). 
Remove the impression (see Fig. 12-35, c, 
evaluate it, and pour the working cast (see 
Fig. 12-35, D) as usual (see Chapter 17). 
NOTE: Access for waxing is generally adequate 

without placement of dowel pins or sectioning of 

the cast. 

7. In the laboratory, roughen a loose-fitting 
plastic post (a plastic toothpick is suitable) 
and, using the impression as a guide, make 
sure that it extends into the entire depth of 
the canal. 

8. Apply a thin coat of sticky wax to the plastic 
post and, after lubricating the stone cast, add 
soft inlay wax in increments (Fig. 12-36). Start 
from the most apical and make sure that the 
post is correctly oriented as it is seated to 
adapt the wax. When this post pattern has 
been fabricated, the wax core can be added 
and shaped. 

Use the impression to evaluate whether the 
wax pattern is completely adapted to the post 
space. 



9. 



CORE FABRICATION 

The core of a post-and-core restoration replaces 
missing coronal tooth structure and thereby forms 





the shape of the tooth preparation. It can be shaped 
in resin or wax and added to the post pattern before 
the assembly is cast in metal. This prevents possible 
failure at the post-core interface. The core can also 
be cast onto most prefabricated post systems (al- 
though there is then some concern that the casting 
process may unfavorably affect the physical proper- 
ties of wrought metal posts). A third alternative is to 
make the core from a plastic restorative material 
such as amalgam, glass ionomer, or composite resin. 

Plastic Filling Materials. The advantages of 
amalgam, glass ionomer, or resin include the 

following: 

1. Maximum tooth structure can be conserved 
because undercuts do not need to be re- 
moved. 

2. Treatment requires one less patient visit. 

3. There are fewer laboratory procedures. 

4. Testing generally shows good resistance to 
fatigue testing71 and good strength character- 
istics, 72 possibly because of the good adapta 
tion to tooth structure. However, these plastic 
restorative materials, especially the glass 
ionomer s, have lower tensile strength than 
do cast metals. 

Disadvantages include the following: 

1. Long-term success may be affected by corro- 
sion of amalgam cores, the low strength of 
glass ionomer' 73 or the continued polymeriza 
tion" and high thermal expansion coeffi- 
cients of composite resin cores. 

2. Microleakage with temperature fluctuations 
(thermocycling) is greater under composite 
resin and amalgam cores than under conven 
tional crown preparations'-' (however, the ex- 
tent of leakage under cast cores has yet to be 
determined). 

3. Difficulty may be encountered with certain 
operative procedures such as rubber dam or 
matrix application (particularly on badly 
damaged teeth). 

Amalgam cores are suitable for restoring posterior 
teeth, particularly when some coronal structure re- 
mains. The procedure described by Nayyar et al, 42 
with amalgam also used for the posts, is conservative 
of tooth structure. The cores are placed during the 
same appointment as the root canal obturation, be- 
cause then the teeth are still isolated by the rubber 
dam, the root canal morphology is still fresh 
in the practitioner's mind, and the cores can serve as 
a support for the provisional restoration (Fig. 12-37). 



Fig. 12-36. Post-and-core patterns made by adding wax 
to prefabricated plastic posts. 



Step-by -Step Procedure for Amalgam (see also 
Chapter 6). 



rhnpter 1 7 Re stnr^tinn of the Endodontic ally Treated Tooth 



I 



1. Apply the rubber dam and remove gutta- 
percha from the pulp chamber as well as 2 to 
4 mm into each root canal if less than 4 mm of 
coronal height remains. Use a warmed en- 
dodontic instrument. 

2. Remove any existing restoration, under- 
mined enamel, or carious or weakened dentin. 
Estabhsh the cavity form using conventional 
principles of resistance and retention form. 
Even if cusps are missing, pins are not nor- 
mally required because adequate retention 
can be gained by extending the amalgam into 
the root canals. 

3. If you suspect that the floor of the pulp cham- 
ber is thin, protect it from condensing pres- 
sures with a cement base. 

4. Fit a matrix band. Where lack of tooth struc- 
ture makes the application of a conventional 
matrix system difficult, an orthodontic or an- 
nealed copper band may be used. 

5. Condense the first increments of amalgam 
(select a material with high early strength) 
into the root canals with an endodontic 
plugger. 

6. Fill the pulp chamber and coronal cavity in 
the conventional manner. 

7. Carve the alloy to shape. The impression can 
be made immediately. Alternatively, the 
amalgam can be built up to anatomic contour 



and later prepared for a com-plete crown. 
Under these circumstances, avoid forces that 
would fracture the tooth or newly placed 
restoration. 

Cast Metal. Cast metal cores have the follow- 
ing advantages: 

1. They can be cast directly onto a prefabricated 
post, providing a restoration with good 
strength characteristics. 

2. Conventional high-noble, metal-content al- 
loys can be used. 

3. An indirect procedure can be used, making 
restoration of posterior teeth easier. 

Direct Procedure for Single-rooted Teeth 

Direct patterns can be formed by combining a 
prefabricated post with autopolymerizing resin. 

Alternatively, a thermoplastic material can be used 
to create a post pattern '16 and the core portion can be 
developed in either autopolymerizing resin, light 
polymerized resin, or wax. 

Pattern Fabrication with Autopolymerizing 
Resin (Fig. 12-38) 

1. Use a prefabricated metal or custom acrylic 
resin post. 

2. Add resin by the "bead" technique, dipping 
a small brush in monomer and then into 




Fig. 12-37. Retention for an amalgam core can be obtained from the root canal system, preserving as 
much tooth structure as possible. 
(B to D courtesy Dr. M. Padilla.) 



I 



Section 2 Clinical Procedures -Part I 




Fig. 1 2-38. Direct pattern for a single-rooted tooth. 



polymer and applying it to the post. Some ex- 
perts recommend light-cured resin to facili- 
tate this step." 

3. Slightly overbuild the core and let it poly- 
merize fully (Fig. 12-38, A). 

4. Shape the core with carbide finishing burs or 
paper disks (Fig. 12-38, B). Use water spray to 
prevent overheating of the acrylic resin. Cor- 
rect any small defects with wax. 

5. Remove the pattern (Fig. 12-38, C; sprue and 
invest it immediately. 

Direct Pattern for Multirooted 

Teeth (Fig. 12-39) 

A direct pattern can be used for multirooted pos- 
terior teeth, although limited access may make the 
indirect approach easier. A single-piece core with 
auxiliary posts is used, as opposed to the multisec- 
tion core recommended for indirect posterior cast 
post-and-cores. The core is cast directly onto the post 
of one canal. (The other canals already have prefab- 
ricated posts that pass through holes in the core.) 




Fig. 1 2-39. A direct post-and-core for posterior teeth 
can be made by cementing a prefabricated post through a 
casting. Here tlie two buccal canals had a common path of 
withdrawal and could be incorporated into the core casting. 
More typically, only one canal has a fixed post, and the oth- 
ers are cemented through the core. 



The procedure is simple, as long as smooth par- 
allel-sided or tapered posts are used. 

1. Fit prefabricated posts into the prepared 
canals. One post is roughened; the others are 
left smooth and lubricated. All posts should 
extend beyond the eventual preparation. 

2. Build up the core with autopolymerizing 
resin, using the bead technique. 

3. Shape the core to final form with carbide fin- 
ishing burs. 

4. Grip the smooth, lubricated posts with for- 
ceps and remove them. 

5. Remove, invest, and cast the core with the 
roughened single post. When this has been 
done, the holes for the auxihary posts can be 
refined with the appropriate twist drill. 

6. After verifying the fit at try-in, cement the 
core and auxiliary posts to place. 

Indirect Pattern for Posterior 
Teeth (Fig. 12-40) 

1. Wax the custom-made posts as described pre- 
viously. 

2. Build part of the core around the first post. 

3. Remove any undercuts adjacent to other post 
holes and cast the first section. 

4. Wax additional sections and cast them. 
Using dovetails to interlock the sections makes 

the procedure more complicated and is probably of 
limited benefit, especially because the final buildup 
is held together by the fixed cast restoration. 

PROVISIONAL RESTORATIONS (sGG Chapter 15) 
To prevent drifting of opposing or adjacent teeth, an 
endodontically treated tooth requires a proper pro- 
visional restoration immediately following comple- 
tion of endodontics (Fig. 12-41). Of particular im- 
portance are good proximal contacts to prevent 



Chapter 1 7 Restoration of the Rndodonticnlly Treated Tooth 



I 




H 



Fig. 12-40. A to D, Multipiece post-and-cores can be made by the indirect technique, waxing each 
section to ensure that no undercuts are created. E to H, Alternatively, interlocking sections can be made, 
but this complicates the laboratory phase. 



tooth migration leading to unwanted root proxim- 
ity. If a cast post-and-core is made, an additional 
provisional restoration is needed while the post- 
and-core is being fabricated. This can be retained by 
fitting a wire (e.g., a paper clip or orthodontic wire) 
into the prepared canal. The restoration is then con- 
veniently fabricated with autopolymerizing resin 
by the direct technique. 



INVESTING AND CASTING 

A cast post-and-core should fit somewhat loosely in 
the canal. A tight fit may cause root fracture. The 
casting should be slightly undersized, which can be 
accomphshed by restricting expansion of the invest- 
ment (i.e., by omitting the usual ring hner or casting 
at a lower mold temperature [see Chapter 22]). An 
accelerated casting technique may facilitate the 



I 



Section 2 Clinical Procedures-Part I 



It is not essential thiit the reline 
material extend all the way down 
the post space. By engaging the 
apical portion of the post space, 
the wije will enhance resistance 
of the provisional. 



Reinforcing 
wire 



Autopolymerizing 
resin 

Preformed 
crown 




Fig. 1 2-41 . Provisional restorations made for endodon- 
tically treated teeth by lining a polycarbonate crown with 
autopolymerizing resin. The post is made of metal wire (or- 
thodontic wire or a paper cHp, [see Chapter 15]). 

(A from Taylor GN, Land MF: In Clark JW, editor: Clinical den- 
tistry, New York, 1985, Harper & Row.) 



laboratory phase. The casting alloy should have 
suitable physical properties. Extra-hard partial den- 
ture gold (ADA Type IV) or nickel chromium alloys 
have high moduli of elasticity and are suitable for 
cast posts. A sound casting technique is essential be- 
cause any undetected porosity could lead to a weak- 
ened casting that might fail in function (Fig. 12-42). 
Casting a core onto a prefabricated post avoids 
problems of porosity, but the preheating temperature 
of the investment mold should be restricted if recrys- 
taUization of the wrought post'" is to be avoided. 




Fig. 1 2-42. Fractured post. 

(Courtesy Dr. D. Francisco.) 



EVALUATION 

The practitioner must be particularly careful that 
casting defects do not interfere with seating of the 
post; otherwise, root fracture will result. Post-and- 
cores should be inserted with gentle pressure. How- 
ever, the marginal fit of a cast foundation is not as 
critical as that of other cast restorations, because the 
margins will be covered by the final casting. Air- 
abrading the surface to a matte-type finish may help 
detect interferences at try- in (Fig. 12-43). 

The shape of the foundation is evaluated and ad- 
justed as necessary. No adjustments should be made 
immediately after cementation because vibration 
from the bur could fracture the setting cement and 
cause premature failure. 

CEMENTATION 

The luting agent must fill all dead space within the 
root canal system (Fig. 12-44). Voids may be a cause 
of periodontal inflammation via the lateral canals. 
A rotary (lentulo) paste filler or cement tube (Fig. 
12-45) is used to fill the canal with cement. The post- 
and-core is inserted gently to reduce hydrostatic 
pressure, which could cause root fracture. If a paral- 
lel-sided post is being used, a groove should be 
placed along the side of the post to allow excess ce- 
ment to escape. 

REMOVAL OF EXISTING POSTS 

Occasionally an existing post-and-core must be re- 
moved (e.g., for retreatment of a failed root canal 
filling). Patients must understand in advance that 
post removal is a risky process and occasionally re- 
sults in radicular fracture. If sufficient length of 
post is exposed coronally, the post can be retrieved 
with thin-beaked forceps. Vibrating the post first 
with an ultrasonic sealer will weaken brittle ce- 
ment and facilitate removal. A thin sealer tip or 



rhapter 1 7 Restoration of the F.ndodon\\r^Uy Treated Tooth 



I 





Fig. 1 2-43. The fitting surface of the casting must be 
carefully evaluated. Any nodules could lead to root fracture 
if undetected. 



Fig. 1 2-44. Residual voids after cementation can cause 

inflammation. 

(Courtesy Dr. D. Francisco. ) 




Fig. 1 2-45. A, Lentulo rotary paste fillers or a cement tube are used to fill the post space completely. 
B, The post is first coated with cement. C, The canal is filled with cement. D, To avoid the risk of frac- 
ture, the post-and-core is very gently seated. A small cement line is not usually significant, because dis- 
solution is prevented by the presence of the definitive restoration. 
(B to D courtesy Dr. M. Padilla.) 



I 



Section 2 Clinical Procedures -Part I 



special post removal tip is recommended (Fig. 
12-46). Although histologic examination with ani- 
mal models shows no harmful effect in the peri- 
odontal tissues, ultrasonic removal is slower than 
other methods and may result in an increased 
number of canal and intradentin cracks." Alterna- 
tively, a post puller can be used .82 This device con- 
sists of a vise to grip the post and legs that bear on 



the root face. A screw activates the vise and ex- 
tracts the post. 

A post that has fractured within the root canal 
cannot be removed with a post puller or forceps. 
The post can be drilled out, but great care is 
needed to avoid perforation. The technique is 
best limited to relatively short fractured posts (Fig. 
12-47). 




Fig. 1 2-46. Post removal by ultrasonic device. A, Preoperative radiograph of the left maxillary first 
premolar with a parallel-sided threaded post that had to be removed for endodontic retreatment. B, Af- 
ter the coronal portion of the post has been well isolated, the tip of the ultrasonic device is placed 
against it, and energy is applied to disrupt the cement interface. Note the suction tip, which removes 
water spray used with the ultrasonic handpiece. C, After a time, the post becomes loose within the canal 
and can be retrieved by forceps. D, Radiograph of the premolar after post removal. 
(Courtesy Dr. L. L. Lazare.) 



Fig. 1 2-47. Post removal by high-speed bur. A, Preoper- 
ative radiograph of the right maxillary lateral incisor, in 
which both the crown and part of a post have been frac- 
tured off. A portion of the Kurer-type, parallel-sided, 
threaded post remains within the canal. B, Because of the 
large diameter of the post and its position within the canal, 
a high-speed handpiece was chosen to drill it out. C, Radio- 
graph to verify the correct orientation of the bur's progress 
inside the canal. With this method of post removal, the op- 
erator must be extremely careful not to let the high-speed 
bur contact the canal wall, which would seriously compro- 
mise tooth structure. D, Radiograph of the incisor after post 
removal and retreatment. 
(Courtesy Dr D. A. Miller) 



A 




Chapter 12 Restoration of the Rnrlorlontirally Treated Tooth 



I 



Another means of handUng an embedded frac- 
tured post (described by Masserann" in 1966) uses 
special hollow end-cutting tubes (or trephines) to pre- 
pare a thin trench around the post (Fig. 12-48). This 
technique has shown success ^^ Retrieval can be facil- 
itated by using an adhesive to attach a hollow tube ex- 
tractor or by using a threaded extractor^^ (Fig. 12-49). 

SUMMARY 

Although the restoration of endodontically treated 
teeth has been rationalized considerably by recent 



laboratory research data, information from con- 
trolled long-term clinical trials is still necessary and 
difficult to obtain. Different clinical procedures have 
been advocated, many of which are successful if 
properly used. Where the crown is preserved, an an- 
terior tooth can be safely restored with a plastic fill- 
ing. To prevent fracture of posterior teeth, cast restora- 
tions providing cuspal coverage are recommended. 

Preserving as much tooth structure as possible is 
important, particularly within the root canal, where 
the amount of remaining dentin may be difficult to 
assess. 




Fig. 12-48. Masserann technique for the removal of fractured posts. A and B, Maxillary incisor with 
a post that has fractured inside the canal. C, The diameter of the post is gauged with a sizing tool. 
D, The selected trephine is carefully rotated counterclockwise to create a narrow channel around the 
post. E, When the instrument has removed sufficient material, the post is recovered. F, The fractured 
crown and post after removal. 



I 



Section 2 Clinical Procedures-Part I 

B 



A 




HK^ii. >-.->-.. 




' • ;. 


#'0^^ 






Fig. 12-49. Post removal by extractor. A, The Thomas (Gonon) post-removing system. It includes pli- 
ers, trephine burs, mandrels, and washers. B, Preoperative radiograph of the left maxillary lateral incisor 
with a post. C, Note the flared shape of the post in this preoperative view and the height of the sur- 
rounding tooth structure. D, A high-speed bur is used to free the post from coronal tooth structure and 
parallel its sides. (NOTE: An ultrasonic device may be used at this point to disturb the cement interface.) 
E, A trephine bur machines the post to the correct diameter and places threads for the mandrel. F, The 
mandrel is threaded onto the post with special washers, which distribute the forces from the extractor 
evenly over the tooth. G, The beaks of the pliers are fitted onto the mandrel; the knob of the pliers is 
then rotated, which separates the beaks, and the post is extruded from the tooth. H, The removed post, 
still attached to the mandrel and pliers. I, Radiograph of the lateral incisor after post removal. 
(Courtesy Dr. D. A. Miller.) 



A post-and-core is used to provide retention and 
support for a cast restoration. It should be of ade- 
quate length for good stress distribution but not so 
long as to jeopardize the apical seal. The safest 
method to create post space is to use a warmed en- 
dodontic plugger to remove the gutta-percha. Ante- 
rior teeth, particularly those with flared or elliptical 



canals, should be built up with a custom cast post- 
and-core, although prefabricated posts can be used 
successfully too. Esthetic post materials should be 
considered if a dark post would ruin an esthetic 
restoration. Amalgam can be used satisfactorily on 
posterior teeth, although a casting may be preferred 
if much coronal tooth structure is missing. 



Chapter 1 7 Restoration of the Rn dodonticnlly Treated Tooth 



I 



Si^idy Q^e^iiam 



1 . what must be determined to ensure that an endodontically treated tooth is ready for subsequent restora- 
tive treatment? 

2. What six Features must be incorporated in fhe tooth preparation for a cast post-ond-core? 

3. Discuss five variabbs that have an impact on retention form breast post-and<ores, 

4. Discuss four different post-ond-core systems, their advantages and disadvantages, and typical indications 
and precautions. 

5. Which canal configurations are circular? Which are elliptical? 

6. Describe recommended step-by-step procedures for the following: 

1. Custom-made direct procedure post-and-core pattern fabrication for a maxJflary second premolar 

2. Amalgam post-and-core on a mandibular molar. 

7. How is a provisional restoration fabricated for a mandibular second premolar that has been prepared for 
a cast post-ond-core? 




C,WSSA<ki} 



anatomic crown: ttie portion of a natural tootli tliat ex- 
tends coronal from the cementoenamel junction- 
called also anatomical crown. 

apex: n, pi apexes: or apices: (1601) 1: the uppermost 
point; the vertex; 2: in dentistry, the anatomic end of 
a tooth root. 

autopolymerlzlng resin: a resin whose polymerization 
is initiated by a chemical activator. 

avulsion: n (1622): a forcible separation or detachment, 
as in a tearing away of a body part surgically or 
accidentally. 

dowel: n (13c): a post, usually made of metal that is 
fitted into a prepared root canal of a natural 
tooth. When combined with an artificial crown or 
core, it provides retention and resistance for the 
restoration. 

elastic: adj (1653): susceptible to being stretched, com- 
pressed, or distorted and then tending to resume 
the original shape. 

elastic modulus: the stiffness or flexibility of a material 
within the elastic range. Within the elastic range, 
the material deforms in direct proportion of the 
stress applied as represented by Hooke's law. 
endoscope: n (1861): a flexible or rigid thin tube used 
for examining the interior of a structure. 

exposure: n (1606) 1: the act of laying open, as a surgi- 
cal or dental exposure 2: in radiology, a measure of 
the roentgen rays or gamma radiation at a certain 
place based on its ability to cause ionization. The 
unit of exposure is the roentgen, called also expo- 
sure dose. 

ferrule: n (15c) 1: a metal band or ring used to fit the 
root or crown of a tooth 2: any short tube or bush- 
ing for making a tight joint. 



monomer: n(1914): a chemical compound that can un- 
dergo polymerization; any molecule that can be 
bound to a similar molecule to form a polymer. 

polymerization: n (1872): the forming of a compound by 
the joining together of molecules of small molecular 
weights into a compound of large molecular weight. 

post-core: see dowel. 

resin: n (14c) l : any of various solid or semisolid 
amorphous natural organic substances that usually 
are transparent or translucent and brown to yellow; 
usually formed in plant secretions; are soluble in or- 
ganic solvents but not water; are used chiefly in var- 
nishes, inks, plastics, and medicine; and are found 
in many dental impression materials 2: a broad term 
used to describe natural or synthetic substances that 
form plastic materials after polymerization. They 
are named according to their chemical composition, 
physical structure, and means for activation of 
polymerization. 

root: n (bef. 12c): the portion of the tooth apical to the 
cementoenamel junction that is normally covered 
by cementum and is attached to the periodontal lig- 
ament and hence to the supporting bone. 

Stress: n (14c): force per unit area; a force exerted on 
one body that presses on, pulls on, pushes against, 
or tends to invest or compress another body; the de- 
formation caused in a body by such a force; an in- 
ternal force that resists an externally applied load or 
force. It is normally defined in terms of mechanical 
stress, which is the force divided by the perpendic- 
ular cross sectional area over which the force is ap- 
plied. 

wax pattern: a wax form that is the positive likeness of 
an object to be fabricated. 



I 



Section 2 Clinical Procedures-Part I 



<k^y^U0<c^s 



1. Johnson JK et al: Evaluation and restoration of 
endodontically treated posterior teeth, J Am Dent 
Assoc 93:597, 1976. 

2. Kakehashi Y et al: A new all-ceramic post and 
core system: clinical, technical, and in vitro re- 
sults, Int J Periodont Restor Dent 18:586, 1998. 

3. Blitz N: Adaptation of a fiber-reinforced restora- 
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cally treated teeth, Pract Periodont A esthet Dent 
10:191, 1998. 

4. Torbjorner A et al: Survival rate and failure char- 

acteristics for two post designs, J Prosthet Dent 
73:439, 1995. 

5. Sorensen JA, Martinoff JT: Clinically significant 
factors in dowel design, J Prosthet Dent 52:28, 
1984. 

6. Loney RW, Moulding MB, Ritsco RG: The effect 
of load angulation on fracture resistance of teeth 
restored with cast post and cores and crowns, 
Int J Prosthodont 8:247, 1995. 

7. Heifer AR et al: Determination of the moisture 
content of vital and pulpless teeth. Oral Surg 
34:661, 1972. 

8. Trabert KC et al: Tooth fracture: a comparison of 
endodontic and restorative treatments, J En- 
dodont 4:341, 1978. 

9. Guzy GE, NichoUs Jl: In vitro comparison of in- 
tact endodontically treated teeth with and with- 
out endo-post reinforcement, J Prosthet Dent 
42:39, 1979. 

10. Hunter AJ et al: Effects of post placement on en- 
dodontically treated teeth, J Prosthet Dent 62:166, 
1989. 

11. Ko CC et al: Effects of posts on dentin stress dis- 
tribution in pulpless teeth, J Prosthet Dent 68:421, 
1992. 

12. Kantor ME, Pines MS: A comparative study of 
restorative techniques for pulpless teeth, J Pros- 
thet Dent 38:405, 1977. 

13. Sorensen JA, Martinoff JT: Intracoronal reinforce- 
ment and coronal coverage: a study of endo- 
dontically treated teeth, J Prosthet Dent 51:780, 
1984. 

14. Lu YC: A comparative study of fracture resis- 
tance of pulpless teeth. Chin Dent J 6:26, 1987. 

15. Warren MA et al: In vitro comparison of bleach- 
ing agents on the crowns and roots of discolored 
teeth, J Endodont 16:463, 1990. 

16. Madison S, Walton R: Cervical root resorption 
following bleaching of endodontically treated 
teeth, J Endodont 16:570, 1990. 

17. McKerracher PW: Rational restoration of 
endodontically treated teeth. I. Principles, 
techniques, and materials, Aust Dent J 26:205, 
1981. 



18. Felton DA et al: Threaded endodontic dowels: 
effect of post design on incidence of root frac- 
ture, J Prosthet Dent 65:179, 1991. 

19. Henry PJ: Photoelastic analysis of post core 
restorations, Aust Dent J 22:157, 1977. 

20. Assif DF et al: Photoelastic analysis of stress 
transfer by endodontically treated teeth to the 
supporting structure using different restorative 
techniques, J Prosthet Dent 61:535, 1989. 

21. Milot P, Stein RS: Root fracture in endodonti- 
cally treated teeth related to post selection and 
crown design, J Prosthet Dent 68:428, 1992. 

22. Sorensen J A, Engelman MJ: Ferrule design and 
fracture resistance of endodontically treated 
teeth, J Prosthet Dent 63: 529, 1990. 

23. Libman WJ, NichoUs JI: Load fatigue of teeth re- 
stored with cast posts and cores and complete 
crowns, Int J Prosthodont 8:155, 1995. 

24. Isidor F et al: The influence of post length and 
crown ferrule length on the resistance to cyclic 
loading of bovine teeth with prefabricated tita- 
nium posts, Int^ Prosthodont 12:78, 1999. 

25. Gegauff AG: Change in strength from creating a 
ferrule via crown-lengthening, J Dent Res 78:223, 
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26. Standlee JP et al: Retention of endodontic dow- 
els: effects of cement, dowel length, diameter, 
and design, J Prosthet Dent 39:401, 1978. 

27. Ruemping DR et al: Retention of dowels sub- 
jected to tensile and torsional forces, J Prosthet 
Dent 41:159, 1979. 

28. Kurer HG et al: Factors influencing the retention 
of dowels, J Prosthet Dent 38:515, 1977. 

29. Cooney JP et al: Retention and stress distribu- 
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Dent 55:540, 1986. 

30. Krupp JD et al: Dowel retention with glass- 
ionomer cement, J Prosthet Dent 41 : 163, 1979. 

31. Wood WW: Retention of posts in teeth with non- 
vital pulps, J Prosthet Dent 49:504, 1983. 

32. Hanson EC, Caputo AA: Cementing mediums 
and retentive characteristics of dowels, J Prosthet 
Dent 32:551, 1974. 

33. Chapman KW et al: Retention of prefabricated 
posts by cements and resins, J Prosthet Dent 
54:649, 1985. 

34. Driessen CH et al: The effect of bonded and non- 
bonded posts on the fracture resistance of 
dentin, J Dent A ssoc S Afr 52:393, 1997. 

35. Mendoza DB, Eakle WS: Retention of posts ce- 
mented with various dentinal bonding cements, 
J Prosthet Dent 72:591, 1994. 

36. O'Keefe KL et al: In vitro bond strength of 
silica-coated metal posts in roots of teeth, Int J 
Pro sthod 5:373, 1992. 

37. Tjan AH, Nemetz H: Effect of eugenol-contain- 
ing endodontic sealer on retention of prefabri- 



Chnptor 1 ?, Restoration of the Endodontically Treated Tooth 



I 



cated posts luted with adhesive composite resin 
cement. Quintessence Int 23:839, 1992. 

38. Radke RA et al: Retention of cast endodontic 
posts: comparison of cementing agents, J Prosthet 
Dent 59:318, 1988. 

39. Love RM, Purton DG: Retention of posts with 
resin, glass ionomer and hybrid cements, J Dent 
26:599, 1998. 

40. Assif D et al: Retention of endodontic posts with 
a composite resin luting agent: effect of cement 
thickness. Quintessence Int 19:643, 1988. 

41. Kane JJ et al: Fracture resistance of amalgam 
coronal-radicular restorations, J Prosthet Dent 
63:607, 1990. 

42. Nayyar A et al: An amalgam coronal-radicular 
dowel and core technique for endodontically 
treated posterior teeth, J Prosthet Dent 43 :5 1 1 , 1980. 

43. Mentink AG et al: Qualitative assessment of 
stress distribution during insertion of endodon- 
tic posts in photoelastic material, J Dent 26:125, 
1998. 

44. Standlee JP et al: The retentive and stress- 
distributing properties of a threaded endodontic 
dowel, J Prosthet Dent 44:398, 1980. 

45. Thorsteinsson TS et al: Stress analysis of four 
prefabricated posts, J Prosthet Dent 67:30, 1992. 

46. Derand T: The principal stress distribution in a 
root with a loaded post in model experiments, 
J Dent Res 56:1463, 1977. 

47. Leary JM et al: Load transfer of posts and cores to 
roots through cements, J Prosthet Dent 62:298, 1989. 

48. Peters MCRB et al: Stress analysis of a tooth re- 
stored with a post and core, J Dent Res 62:760, 
1983. 

49. Yaman SD, Alacam T, Yaman Y: Analysis of 
stress distribution in a maxillary central incisor 
subjected to various post and core applications, 
J Endodont 24:107, 1998. 

50. Schnell FJ: Effect of immediate dowel space 
preparation on the apical seal of endodontically 
filled teeth. Oral Surg 45:470, 1978. 

51. Bourgeois RS, Lemon RR: Dowel space prepara- 
tion and apical leakage, j Endodont 7:66, 1981. 

52. Gegauff AG et al: A comparative study of post 
preparation diameters and deviations using 
ParaPost and Gates-Glidden drills, J Endodont 
14:377, 1988. 

53. Hussey Dl et al: Thermographic assessment of heat 
generated on the root surface during post space 
preparation, Int Endodont J 30:187, 1997. 

54. Dickey DJ et al: Effect of post space preparation 
on apical seal using solvent techniques and 
Peeso reamers, j Endodont 8:351, 1982. 

55. Caputo AA, Standlee JP: Pins and posts: why, 
when, and how. Dent Clin North Am 20:299,1976. 

56. Shillingburg HT et al: Root dimensions and 
dowel size, Calif Dent Assoc i 10(10):43, 1982. 



57. Abou-Rass M et al: Preparation of space for 
posting: effect on thickness of canal walls and 
incidence of perforation in molars, J Am Dent 
Assoc 104:834, 1982. 

58. Perez Moll JF et al: Cast gold post and core and 
pin-retained composite resin bases: a comparative 
study in strength, J Prosthet Dent 40:642, 1978. 

59. Phillips RW: Skinner's science of dental materials, 
ed 9, Philadelphia, 7997, WB Saunders, p 550. 

60. Asmussen E, Peutzfeldt A, Heitmann T: Stiff- 
ness, elastic limit, and strength of newer types of 
endodontic posts, J Dent 27:275, 1999. 

61. Frederiksson M et al: A retrospective study of 
236 patients with teeth restored by carbon fiber 
epoxy resin posts, J Prosthet Dent 80:151,1998. 

62. Martinez-Insua A et al: Comparison of the frac- 
ture resistances of pulpless teeth restored with a 
cast post and core or carbon-fiber post with a 
composite core, J Prosthet Dent 80:527, 1998. 

63. Kakehashi Y et al: A new all-ceramic post and 
core system: clinical, technical, and in vitro re- 
sults, Int J Periodont Restor Dent 18:586, 1998. 

64. Ahmad 1: Zirconium oxide post and core system 
for the restoration of an endodontically treated 
incisor, Pract Periodont Aesthet Dent 11:197, 1999. 

65. Sirimai S et al: An in vitro study of the fracture 
resistance and the incidence of vertical root frac- 
ture of pulpless teeth restored with six post-and- 
core systems, J Prosthet Dent 81: 262, 1999. 

66. Rud J, Omnell KA: Root fractures due to corro- 
sion: diagnostic aspects, Scand J Dent Res 78:397, 
1970. 

67. Angmar-Manansson B et al: Root fracture due to 
corrosion. I. Metallurgical aspects, Odontol Rev 
20:245, 1969. 

68. Silness J et al: Distribution of corrosion products 
in teeth restored with metal crowns retained by 
stainless steel posts. Acta Odontol Scand 37:3 17, 
1979. 

69. Chan RW, Bryant RW: Post-core foundations for 
endodontically treated posterior teeth, J Prosthet 
Dent 48:401, 1982. 

70. Lovdahl PE, NichoUs JI: Pin-retained amalgam 
cores vs. cast-gold dowel-cores, J Prosthet Dent 
38:507, 1977. 

71. Reagan SE et al: Effects of cyclic loading on se- 
lected post-and-COre systems. Quintessence Int 30: 
61, 1999. 

72. Foley J, Saunders E, Saunders WP: Strength of 
core build-up materials in endodontically 
treated teeth. Am J Dent 10:166, 1997. 

73. Kovarik RE et al: Fatigue life of three core mate- 
rials under simulated chewing conditions, 

J Prosthet Dent 68:584, 1992. 

74. Oliva RA, Lowe JA: Dimensional stability of 
composite used as a core material, J Prosthet 
Dent 56:554, 1986. 



I 



Section 2 Clinical Procedures-Part I 



75. Larson TD, Jensen JR: Microleakage of compos- 
ite resin and amalgam core material under com- 
plete cast crowns, J Pwsthet Dent 44:40, 1980. 

76. Rosenstiel SF et al: Custom-cast post fabrication 
with a thermoplastic material, J Pwsthet Dent 11: 
209, 1997. 

77. Waldmeier MD, Grasso JE: Light-cured resin for 
post patterns, J Pwsthet Dent 68:412, 1992. 

78. Campagni WV, Majchrowicz M: An accelerated 
technique for the casting of post and core 
restorations, J Pro Sthet Dent 66:155, 1991. 

79. Brunell G: Casting and microstructure of post 
and core at different mold temperatures. Acta 
Odontol Scand 40:241, 1982. 

80. Yoshida T et al: An experimental study of the re- 
moval of cemented dowel-retained cast cores by 
ultrasonic vibration, J Endodont 23:239, 1997. 

81. Altshul JH et al: Comparison of dentinal crack 
incidence and of post removal time resulting 



from post removal by ultrasonic or mechanical 
force, J Endodont 23:683, 1997. 

82. Warren SR, Gutmann JL: Simplified method for 
removing intraradicular posts, J Pwsthet Dent 
42:353, 1979. 

83. Masserann J: The extraction of posts broken 
deeply in the roots. Actual OdontOStomatol 75:329, 
1966. 

84. Williams VD, Bjorndal AM: The Masserann tech- 
nique for the removal of fractured posts in en- 
dodontically treated teeth, J Pwsthet Dent 49:46, 
1983. 

85. Gettleman BH et al: Removal of canal obstruc- 
tions with the Endo Extractor, J Endodont 17:608, 
1991. 

86. Machtou P et al: Post removal prior to retreat- 
ment, J Endodont 15:552, 1989. 






»->^«>iHT I IT- tl 



C H A P T E 



H 1 RT E E N 



Implant-Supported 
.Fixed Prostheses 



cover screw 
dental implant 
fixed abutment 
healing abutment 
healing cap 
hybrid prosthesis 
i mplant abutment types 
i mplant analog 
implant angulation 



implant body 
implant placement 
implant prosthodontics 
implant substructure 
implant surgery 
osseointegration 
peri-implantitis 
transosteal dental implant 



Today the continued high rate of success achieved 
with osseointegrated dental implants allows a 
greater number of patients to enjoy the benefits of 
fixed rather than removable restorations. The 
main indications for implant restorations in the par- 
tially edentulous patient are the free-end distal ex- 
tension where no posterior abutment is available 
(Fig. 13-1) and the long edentulous span. In both 
these situations, the conventional dental treatment 
plan would include a removable partial denture. 
However, with the advent of implant abutments, 
the patient can benefit from fixed restorations. Ad- 
ditionally, in the short edentulous span, the single 
implant is a popular option (Fig. 13-2). 

IMPLANT TYPES 

There are three major subgroups of dental implants: 
subperiosteal, transosteal, and endosteal (Fig. 13-3). 
The first two, subperiosteal and transosteal, are de- 
signed primarily to anchor dentures in the com- 
pletely edentulous patient and thus fall outside the 
scope of this chapter. The third, endosteal implants, 
are surgically placed within alveolar or basal bone 
and are most commonly used for the treatment of 
partially edentulous patients, either singly or in 
multiples. They can be further subdivided by shape 
into blade form (plateform) and root form (cylindri- 
cal). Blades are wedge shaped or rectangular in 
cross section and are generally 2.5 mm wide, 8 to 15 




B 



Fig. 13-1. A, Radiograph of two-unit fixed partial den- 
ture supported by two dental implants. B, Clinical example 
of bilateral two-unit fixed partial dentures. 



mm deep, and 15 to 30 mm long. Root forms are 3 to 
6 mm in diameter and 8 to 20 mm long, often with 
external threads (Fig. 13-4). Endosteal implants are 
also categorized as one stage or two stage. The 
one- stage implant is designed to be placed in the 
bone and to immediately project through mucosa 



313 



I 



Section 2 Clinical Procedures-Part I 



A 




Fig. 13-2 . A, Single-tooth implant abutment tightened to place. B, Implant crown replacing a single 
missing tooth (cement retained). 




Fig. 13-3. xhe three major subgroups of dental implants. A, Subperiosteal. B, Transosteal. C and D, 
Endosteal. Endosteal implants can be further subdivided into plate form (C) and root form (D). 




Fig. 13-4 . Common types of root- form implants. Left to 
right: titanium screw, titanium alloy hollow basket, tita- 
nium plasma-sprayed cylinder, hydroxyapatite-coated 
cylinder. 

into the oral cavity. The two- stage implant requires 
two surgical procedures. First, the implant is placed 
in bone to the level of the cortical plate and the oral 
mucosa is sutured over it; this is left for a prescribed 



healing period (usually 3 months in the mandible 
and 6 to 9 months in the maxilla), depending on the 
quality of bone. Then, in a second surgery, the mu- 
cosa is reflected from the superior surface of the im- 
plant, and an extension collar or abutment that pro- 
jects into the oral cavity is fastened to the implant. 
Some authors have suggested shortening the time 
before implant loading, but the long-term conse- 
quences of this are unknown. 

PLATE IMPLANTS (BLADES) 

Blades were the first dental implant to experience 
reasonable success in a large number of patients. All 
the original studies on blades used one-stage sys- 
tems, but the success rates were considerably lower 
than those of current root-form implants. It has been 
suggested 6 that many of the problems of blade im- 



Chapter 13 Implant- Supported Fixed Prostheses 



I 



plants can be traced to the high temperature at 
which the bone sites were prepared and the routine 
immediate loading of this type of implant. Both 
these practices have been linked to the fibrous en- 
capsulation that occurred with many of the original 
blade implants. Consequently, submergible tita- 
nium blades are now available, and more recent 
blade studies' have reported success rates above 
80% for 5 years. However, the drawbacks to blade 
implants remain- difficulty of preparing precision 
slots for blade placement compared to placing holes 
accurately for root-form implants and the disas- 
trously large circumferential area of the jaw that can 
be affected when a blade fails. 

ROOT- FORM IMPLANTS (CYLINDERS) 
Cylindrical root-form dental implants are consid- 
ered to be state-of-the-art implant dentistry. Advan- 
tages include adaptability to multiple intraoral loca- 
tions, uniformly precise implant- site preparation, 
and comparatively low adverse consequences simi- 
lar to that experienced when a tooth is lost. Most 
root forms are made of titanium or titanium alloy 
with or without hydroxyapatite coating, materials 
that are perceived to have the highest biofunctional- 
ity. Both threaded and nonthreaded designs are 
available and are quite popular. Today many of the 
titanium implants are grit blasted or acid etched to 
roughen the surface and increase the area for bone 
contact. 

The NIH consensus conference' in 1988 reported 
that root-form implants already constituted 78% of 
the implant market. This trend is credited to the 
Branemark system, which set the precedent for sur- 
gical techniques and restorative procedures that re- 
sult in predictably successful implants. Two of the 
most important additions from the Swedish re- 
search team, led by PI. Branemark, were atraumatic 
implant placement and delayed implant loading. 
These factors contributed to a remarkably increased 
degree of implant predictability. The original Brane- 
mark success rate of 91% in the mandible over 15 
years' has become the benchmark by which other 
implant systems are judged." Many of the other 
root- form implant systems are also believed to have 
reached or exceeded this high level of long-term 
success. 



TREATMENT PLANNING FOR THE 
IMPLANT PATIENT 

Implant success reported from major research insti- 
tutions is quite high. However, meticulous attention 
to the procedures of patient selection, diagnosis, and 
treatment planning is required to duphcate this suc- 



cess. Indications for dental implant treatment in the 
partially edentulous patient are provided in Box 13-1. 

A combined surgical and restorative treatment 
plan must be devised for prospective implant pa- 
tients. Feasible nonimplant alternatives should be 
included in the overall treatment discussions. Pa- 
tients need to be evaluated preoperatively and as- 
sessed as to whether they will be able to tolerate the 
procedure. The predictable risks and expected bene- 
fits should be weighed for each person. Although 
the placement of dental implants does entail some 
risks, they are relatively minor. Absolute contraindi- 
cations, based on immediate surgical and anesthetic 
risks, are limited to individuals who are acutely ill, 
individuals with uncontrolled metabolic disease, 
and pregnant women (contraindications that apply 
to virtually all elective surgical procedures). 

Local and systemic contraindications that 
threaten long-term implant retention must also be 
evaluated. Implants may be contraindicated in pa- 
tients with abnormal bone metabolism, poor oral 
hygiene, and previous radiation to the implant site. 
Most potential implant placement patients became 
edentulous or partially edentulous from caries and 
periodontal disease resulting from poor oral hy- 
giene. Suspicion that inadequate hygiene will con- 
tinue is a relative contraindication to implant place- 
ment. Patients must be motivated and educated in 
oral hygiene techniques as part of their preparation 
for implants. Some individuals, such as those suf- 
fering from paralysis of the arms, debilitating 
arthritis, cerebral palsy, and severe mental retarda- 
tion, may not be able to improve their hygiene. Im- 
plants are contraindicated in these patients unless 
adequate oral hygiene wiU be provided by caregivers. 
A summary of contraindications to implant place- 
ment is presented in Box 13-2. 

CLINICAL EVALUATION 

Evaluation of the planned implant site begins with 
a thorough clinical examination. This examination 
will determine whether there is adequate bone and 



Indications for implant 
Placement in the Partially 
Edentulous Patient 



BOX IS'I 



1 . inability to wear o removable partial or complete den- 
ture 

2. Need for long -span fixed partial denture with question- 
able prognosis 

3. Unfavoroble number and location of potential natural 
tootfi abutments 

4. Single too^h los^ tbot would necessitate preparation of 
minimally restored teeth for fixed prosthesis 



I 



Section 2 Clinical Procedures -Part I 



will identify anatomic structures that could inter- 
fere with ideal implant placement. Visual inspection 
and palpation allow the detection of flabby excess 
tissue, bony ridges, and sharp underlying osseous 
formations and undercuts that would limit implant 
insertion. However, clinical inspection alone may 
not be adequate if there is thick overlying soft tissue 
that is dense, immobile, and fibrous. 

RADIOGRAPHIC EVALUATION 

Radiographic evaluation is also necessary. The best 
initial film is the panoramic view. However, there 
can be variations in magnification (5% to 35%); a 
small radiopaque reference object should therefore 
be placed near the proposed implant placement site 
during the exposure (Fig. 13-5). Measurement of 
this image on the actual radiograph will enable the 
practitioner to correct for any magnification error 
(Fig. 13-6). A ball bearing placed in wax on a den- 
ture baseplate or in poly (vinyl siloxane) impression 
putty works well. Some new panoramic radiogra- 
phy machines have standardized enlargement ra- 
tios, which makes correction markers less necessary. 




Acute illness 

2. Terminal illness 

3. Pregnancy 

4. Uncontrolled metabolic disease 

5. Tumoricidal radiation to the implant site 

6. Unrealistic patient expectation 

7. Improper patient motivation 

8. Lack of operator experience 

9. Inability to restore with a prosthesis 



The widths of the posterior mandible and maxilla 
are determined primarily by clinical examination. 
Bone width not revealed on a panoramic film can be 
evaluated in the anterior maxilla and mandible with 
a cephalometric film (Fig. 13-7). The location of the 
inferior alveolar canal and maxillary sinus can be 
determined by specialized CT scans, although high 
radiation exposure and considerable expense may 
limit their routine use. 

DIAGNOSTIC CASTS 

Accurately mounted diagnostic casts (see Chapter 2) 
are essential for treatment planning. They are used to 
study the remaining dentition, evaluate the residual 
bone, and analyze maxillomandibular relationships. 
They can be helpful to the surgeon for fixture place- 
ment. A diagnostic waxing is done on the cast or on 
a duplicate. Proposed fixture installation sites are 
checked for proper alignment, direction, location, 
and relation to the remaining dentition. The waxing 
helps determine the most esthetic placement of the 




Fig. 1 3-5. Ball bearings (5-mm diameter) placed on the 
diagnostic cast at the proposed implant site. 




Fig. 1 3-6. A panoramic radiograph exposed with the ball bearings positioned intraorally with a wax or 
resin baseplate. 



Chapter 13 Implant- Supported Fixed Prostheses 



I 



teeth to be restored and the potential for functional 
speech disturbances. After adjustments and the diag- 
nostic waxing are completed, a resin template can be 
made from the cast to guide the surgeon during im- 



plant placement (Fig. 13-8). Diagnostic waxings and 
surgical templates are essential when planning im- 
plants as part of a full-mouth reconstruction or when 
restoring the anterior esthetic zone (Fig. 13-9). 




Fig. 13-7. The lateral cephalometric radiograph can indicate bone 
width in the anterior midline. 



CD 




Fig. 13-8. A, Mounted diagnostic casts show an edentulous ridge and the interarch distance. B, Diag- 
nostic waxing of a three-unit fixed prosthesis to replace the posterior teeth. C, To fabricate the surgical 
template, an alginate impression is made of the diagnostic waxing. D, An impression is poured to make 
a stone cast of the diagnostic waxing. E, A 1.5-mm vacuum- formed matrix is adapted to the stone cast. 
F, The matrix is trimmed from the duplicate cast and returned to the partially edentulous cast. The hol- 
low matrix area is filled with autopolymerizing clear resin. The resin can be trimmed and holes drilled 
to guide the surgeon during implant site preparation (G). 



I 



Section 2 Clinical Procedures-Part I 



BONE SOUNDING 

When the results of clinical and radiographic exam- 
inations are equivocal and additional information is 
needed, sounding of the bone with a probe may be 



attempted. Under local anesthesia, a needle or 
sharp caliper is pushed through the tissue until it 
contacts bone. This can help judge soft tissue thick- 
ness at the planned implant sites. 




Fig. 13-9. A, Diagnostic cast with missing maxillary left lateral incisor. B, The denture tooth is posi- 
tioned for optimum esthetics. C, The denture tooth is trimmed from the lingual side until it is 2 mm 
thick. D, If the tooth is held in position with light-cured composite, a vacuum matrix can be performed 
directly without duplicating the cast. E, The matrix can be trimmed to the height of contour with a stiff 
bristle brush. F, The denture tooth can be glued back into the matrix. G and H, The surgeon can use this 
template to guide both horizontal and vertical positioning. 



Chapter 1 3 Implant-Supported Fixed Prostheses 



I 



PRINCIPLES OF IMPLANT LOCATION 

ANATOMIC LIMITATIONS 

To maximize the chance of success, the implant 
should be placed entirely within bone and away 
from significant anatomic structures (e.g., the infe- 
rior alveolar canal). Ideally, 10 mm of vertical bone 
dimension and 6 mm of horizontal should be avail- 
able for implant placement. These dimensions will 
prevent encroachment on anatomic structures and 
allow 1.0 mm of bone on both the lingual and the fa- 
cial aspect of the implant. There should also be ade- 
quate space between adjacent implants. The mini- 
mum recommended distance varies slightly among 
implant systems but is generally accepted as 3.0 mm 
(Fig. 13-10). This space is needed to ensure bone vi- 
ability between the implants and to allow adequate 
oral hygiene once the restorative dentistry is com- 
plete. Specific limitations due to anatomic varia- 
tions among different areas of the jaws also must 
be considered. These include implant length, diam- 
eter, proximity to adjacent structures, and time re- 
quired for integration. 

The anterior maxilla, posterior maxilla, anterior 
mandible, and posterior mandible each require spe- 
cial considerations in placing implants. Some com- 
mon guidelines include staying 2.0 mm above the 
superior aspect of the inferior alveolar canal, 5.0 mm 
anterior to the mental foramen, and 1.0 mm from the 
periodontal ligament of adjacent natural teeth. 

After tooth loss, resorption of the ridge follows a 
pattern that results in crestal bone thinning and a 




Fig. 13-10. Recoininended rniniinuin distances (in rnil- 
limeters) between implants and between implants and nat- 
uralteeth. 



change in angulation of the residual ridge. These se- 
quelae most often cause problems in the anterior 
mandible and maxilla. The irregular anatomy of the 
residual ridge may lead to problems with achieving 
ideal implant angulation or adequate bone thick- 
ness along the labial aspect of the implant. Tech- 
niques for the management of these problems dur- 
ing surgery will be discussed, but they must be 
anticipated in the preoperative phase. 

Anterior Maxilla. The anterior maxilla must be 
evaluated for proximity to the nasal cavity. A mini- 
mum of 1.0 mm of bone should remain between the 
apex of the implant and the nasal vestibule. Due to 
resorption of the anterior maxilla, the incisive 
foramen may be located near the residual ridge, 
especially in patients whose edentulous maxilla 
has been allowed to function against a natural 
mandibular anterior dentition. Anterior maxillary 
implants should be located slightly off midline, on 
either side of the incisive foramen. 

Posterior Maxilla. Implant placement in the 

posterior maxilla poses two specific concerns: 

First, the bone of the posterior maxilla is less 
dense than that of the posterior mandible. It has 
larger marrow spaces and a thinner cortex, which 
can affect treatment planning, since increased time 
must be allowed for integration of the implants and 
additional implants may be needed. A minimum of 
6 months is usually needed for adequate integration 
of implants placed in the maxilla. In addition, one 
implant for every tooth that is being replaced is nor- 
mally recommended, especially in the posterior 
maxilla. 

The second concern is that the maxillary sinus is 
close to the edentulous ridge in the posterior max- 
illa. Frequently, because of the resorption of bone 
and increased pneumatization of the sinus, only a 
few millimeters of bone remain between the ridge 
and the sinus (Fig. 13-11, A). In treatment planning 
for implants in the posterior maxilla, the surgeon 
should leave 1.0 mm of bone between the floor of 
the sinus and the implant so the implant can be an- 
chored apically into cortical bone of the sinus floor. 
Adequate bone height for implant stability can usu- 
ally be found between the nasal cavity and the max- 
illary sinus. If there is not adequate bone for implant 
placement and support, bony augmentation through 
the sinus should be considered (Fig. 13-11). 

Anterior Mandible. With respect to anatomic 
Umitations, the anterior mandible is usually the 
most straightforward area for treatment planning. It 
usually has adequate height and width for implant 



I 



Section 2 Clinical Procedures-Part I 







^k* 





Fig. 13-11. A, The arrow denotes thin maxillary bone 
inferior to the sinus, which would be inadequate for im- 
plant placement without additional grafting procedures. 
B, The patient, successfully treated with dental implants af- 
ter graft placement. 



placement, and the bone quality is normally excel- 
lent, which makes it require the least amount of 
time for integration. Some success with immediate 
loading of implants in the anterior mandible has 
even been reported. 

When possible, an implant in the anterior 
mandible should be placed through the entire cancel- 
lous bone so the apex of the implant will engage the 
cortex of the inferior mandibular border (Fig. 13-12). 
In the premolar area, care must be taken that the im- 
plant does not impinge on the inferior dental nerve. 
Since this nerve courses as much as 3.0 mm anterior 
to the mental foramen before turning posteriorly and 
superiorly to exit at the foramen, an implant should 
be at least 5.0 mm anterior to the foramen. 

Posterior Mandible. The posterior mandible 
poses some limitations on implant placement. The 
inferior alveolar nerve traverses the mandibular 
body in this region, and treatment planning must al- 
low for a 2.0-mm margin from the apex of the im- 



Suijeriyrroiijcat 
fc plate 



^^^^ 






my 



.^'^d3 










t^'iO ■';,'■'? -^.''0" 






■. .P, 












Fig. 13-12. Whenever possible, implants should engage 
two cortical plates of bone. 




Fig. 1 3-1 3. Shorter implants usually have two prob- 
lems: (1) less bone contact and (2) longer crowns, which in- 
crease the forces acting on the implant. 



plant to the superior aspect of the inferior alveolar 
canal. This is an important guideline: disregarding 
it can cause damage to the nerve and numbness of 
the lower lip. If adequate length is not present for 
even the shortest implant, nerve repositioning, on- 
lay grafting, or a conventional nonimplant-borne 
prosthesis must be considered. 

Implants placed in the posterior mandible are 
usually shorter, do not engage cortical bone inferi- 
orly, and must support increased biomechanical oc- 
clusal forces once they are loaded due to their loca- 
tion in the posterior area. Consequently, allowing 
slightly more time for integration may be beneficial. 
In additional, if short implants (8 to 10 mm) are 
used, "overengineering" and placing more implants 
than usual to withstand the occlusal load is recom- 
mended. Short implants are often necessary because 
of bone resorption, thus increasing the crown-to-im- 
plant ratio when the normal plane of occlusion is 
reestablished (Fig. 13-13). 

The width of the residual ridge must be carefully 
evaluated in the posterior mandible. Attachments of 
the mylohyoid muscle maintain it along the supe- 
rior aspect of the ridge, and a deep (lingual) depres- 
sion exists immediately below it. This area should 



dn-i!^ 



Chapter 13 Implant- Supported Fixed Prostheses 
B C D 



I 




Fig. 13-14. Implant placement and angulation dictate the screw emergence position and crown con- 
tours. Esthetics and access for hygiene can be greatly affected. A, The natural tooth. B, Ideal implant lo- 
cation with acceptable crown contours and lingual screw emergence. C and D, Less ideal implant loca- 
tion. E, Laboratory example of an implant placed too far apically and facially. F, Clinical example of an 
implant placed too far lingually. 



be palpated at the time of evaluation and examined 

at surgery: 

RESTORATIVE CONSIDERATIONS 

Implant Placement. Implant placement is criti- 
cally important to the design of the restoration. Thus 
the treatment-planning aspects of implant place- 
ment must begin with a restorative dentistry consul- 
tation. Implant placement dictates the appearance, 
contour, and long-term function of the prosthesis. To 
prevent damage, staying at least 1.0 mm away from 
the adjacent natural tooth is essential, but staying as 
close to the natural tooth as possible is also impor- 
tant, so acceptable contours can be created by the 
restorative dentist. For proper access during oral hy- 
giene procedures, a minimum of 3.0 mm should be 
left between implants. In addition, implants must 
not encroach on the embrasure spaces or be angled 
so that screw access is necessary through the facial 
surfaces of the completed restoration (Fig. 13-14). 

To minimize harmful lateral forces, the long axis 
of the implant should be positioned in the central 
fossae of the restoration. This dictates placing the 
implant accurately in all three planes of space. Su- 
peroinferior placement is important to ensure the 
optimal emergence profile of the restoration. Ide- 
ally, the superior surface of the implant should be 
2.0 to 3.0 mm directly inferior to the emergence po- 



sition of the planned restoration, particularly when 
the restoration is to be located in the anterior es- 
thetic zone (see Fig. 13-15). 

Implant and Restoration Size. The choice of 
implant and its superior- inferior placement location 
are modified by the diameter of the intended 
restoration and can be adjusted for different sizes of 
teeth. 

For example, the typical root diameter of a max- 
illary central incisor is 8.0 mm; the average implant 
diameter is 4.0 mm. Therefore, a distance of 2.0 to 
3.0 mm is needed to make the transition gradually 
from 4.0 to 8.0 mm. If this is done over too short a 
distance, the restoration will be overcontoured or 
look unnatural. By contrast, many mandibular cen- 
trals and laterals are smaller than 4.0 mm at the 
cementoenamel junction. Therefore, an esthetic 
restoration on a 4.0-mm implant is impossible. 
Smaller-diameter implants (about 3.0 mm) have 
been developed to allow esthetic restoration in 
these areas. It is also possible to use a larger implant 
(5.0 to 6.0 mm) for molar restorations with adequate 
bone (Fig. 13-16). 

Restoration size must always be considered 
during the treatment-planning stage so that a 
properly sized implant will be placed in the ideal 
location. 



I 



Section 2 Clinical Procedures-Part I 




Fig. 13-15. Superior or inferior positioning may affect crown 
contours and pocket depth. A, The implant is not placed deep 
enough. This creates a short, overcontoured crown. B, Placement 
2 to 3 mm apical to the tooth emergence position is ideal. C, Plac- 
ing the implant 4 mm apical to the crown contours may create an 
excessively deep gingival sulcus. D to H, Clinical example of a 
properly positioned implant, both facially and apically, resulting 
in good esthetics. 




Chapter 13 Implant- Supported Fixed Prostheses 



1 



A 




Fig. 13-16. A, Small-diameter implant and abutment positioned to restore a mandibular lateral 
incisor. The fixed abutment can be custom prepared and narrowed to allow restoration of a small- 
diameter tooth. B, Completed implant restoration of the mandibular lateral incisor. C, Wide-diameter 
(5.0 mm) implant in position to replace maxillary first molar. D, Completed implant restoration of the 
maxillary first molar. 




Fig. 13-17. A, Scanning electron micrograph (SEM) of 
the standard external hexagon on an implant and corre- 
sponding abutment. B, SEM of six finger projections from 
an implant (known as a spline interface). 



Single Tooth Implant. Treatment planning for 
the single tooth restoration, particularly in the ante- 
rior esthetic zone, is one of the most challenging 
problems faced by the implant restorative dentist. 
Placement of the implant for both esthetics and bio- 
mechanical loading (to minimize screw loosening) 
is especially critical. In addition, at the treatment- 
planning stage, the decision to place an implant 
with an antirotational feature built into the system 
(e.g., a spline or a hexagon) is essential (Fig. 13-17). 



(]SURGICAL GUIDE 

The coordination of surgical and prosthetic proce- 
dures through proper treatment planning is one of 
the more critical factors in obtaining ideal esthetic 
results for the implant restoration. A surgical guide 
template is extremely useful for anterior implants 
because slight variations in angulation can signifi- 
cantly affect the appearance of the final restoration. 
Construction of the surgical guide template has be- 
come a requirement in those patients in whom it is 
necessary to optimize fixed replacement and ensure 
correct emergence profiles. Surgical templates can 
also be beneficial in areas where esthetics is less im- 
portant. The objectives for using a surgical template 
in partially edentulous patients are as follows: 
(1) delineate the embrasures, (2) locate the implant 
within the restoration contour, (3) align implants 
with the long axis of the completed restoration, and 
(4) identify the level of the CEJ or tooth emergence 
from the soft tissue. 

A clear resin facial veneer template is recom- 
mended for anterior implant placement to allow the 
surgeon access to the osseous receptor site and an 
unimpeded view of the frontal and sagittal angula- 
tions as the site is being prepared. This type of tem- 
plate is fabricated from a diagnostic waxing or den- 
ture tooth arrangement on a mounted cast. The 



■ 



Section 2 Clinical Procedures -Part I 



waxing is duplicated with alginate or poly(vinyl 
siloxane) and poured in quick- setting stone. Then 
1.5 mm (0.060 inch) of vacuum-formed matrix ma- 
terial is adapted to the replicated cast. For accurate 
orientation, the vacuum-formed matrix should be 
trimmed to extend over the full facial surface of the 
teeth being restored and about a third of the facial 
surface of the remaining dentition. This template is 
removed from the duplicate cast and returned to the 
original cast. A 2-mm thickness of autopolymeriz- 
ing resin is added to the lingual surface to compen- 



sate for the space occupied by the porcelain on the 
implant restoration (Fig. 13-18). (The total thickness, 
including an additional miUimeter from the vacuum- 
formed matrix, will be about 3.0 mm.) The surgeon 
must stay as close as possible to this guide during 
implant placement, which will allow maximum 
flexibility in selecting an implant site without vio- 
lating the facial surface or forcing screw access holes 
to be located inappropriately in the facial restora- 
tion. Following this guide will enable the surgeon to 
place a fixture in the best location with minimum 




Fig. 13-18. Anterior surgical guide template fabrication. A, The apical extent of the template is 
not removed, which allows the superior-inferior orientation of implant placement to be determined. 
B, Full-thickness flap incisions are made, preserving the interdental papilla. C, A tissue flap is reflected 
to expose bone for preparation of the implant site. D, Resin (2.0 mm) has been added to the lingual as- 
pect of the matrix; the rest of the lingual area was left open so the surgeon can choose the best available 
bone. The site should be prepared as close to the template as possible. E, The implant is tapped into po- 
sition at an angle that allows optimum esthetics and access for hygiene. F, The implant is positioned 2.0 
to 3.0 mm apical to the desired emergence position of the final restoration. G, The surgical site is su- 
tured. A 6-month healing time will be allowed. 
(Courtesy Dr. J.A. Hollow ay.) 



Chapter 13 Implant-Supported Fixed Prostheses 



■ 



undesirable sagittal angulation. If a cement-retained 
restoration is desired, the orientation of the implant 
can be slightly more facial. 

Although the use of a guide is most necessary in 
the maxillary anterior region, where bony dimen- 
sions are sometimes surprising and often unfavor- 
able, the guide may also be useful in posterior areas 
with wide edentulous ridges. However, a different 
type of guide or template is fabricated in this area. 
Holes are drilled through the resin into the underly- 
ing cast and are paralleled with a milling machine 
or dental surveyor. Such templates even more accu- 
rately locate the placement of an implant and direct 
the inclination of its long axis. 

Surgical templates also can be fabricated for a 
maxillary edentulous arch that is to be restored with 
a fixed prosthesis. Such templates are described 
later in the chapter, but the same preoperative plan- 
ning and interspecialty cooperation are as impor- 
tant here as was just described. 



% 



IMPLANT SURGERY 



Peter E. Larsen 

Implant surgery can be performed in an ambula- 
tory setting under local anesthesia. However, it re- 
quires more time than other surgical procedures, so 
conscious sedation may be preferred. Although 
placing an implant is less traumatic than extracting 
a tooth, patients expect it to be more traumatic. Pre- 
operative education and conscious sedation should 
lessen the anxiety. 

For a complete description of the surgical proce- 
dures involved in implant placement, refer to one of 
the current standard texts. 

SURGICAL ACCESS 

Several types of incision can be used to gain access 
to the residual ridge for implant placement. The in- 
cision chosen should allow retraction of the soft tis- 
sue for unimpeded implant placement and should 
preserve attached tissue esthetics and quantity. 

When the quantity of attached tissue is adequate 
and the underlying bone is expected to be of suffi- 
cient width, a simple crestal incision is recom- 
mended. However, closure must be performed care- 
fully, because the implant lies directly beneath. In 
the posterior mandible, an incision may be placed 
toward the buccal aspect of the ridge to allow the 
flap to be retracted by a suture. This may be a dis- 
advantage, however, because the incision line is 
then immediately over the area where the bone may 
be thinnest, and a dehiscence can occur during 
surgery. An incision slightly to the palatal side is 
particularly effective in the maxillary anterior zone. 



After the bone is exposed, the surgical template is 
positioned, and a periodontal probe is used to make 
a preliminary assessment of the potential implant 
site. The residual ridge may have areas that are un- 
even or with sharp ridges. These areas should be 
smoothed before implant placement. 

IMPLANT PLACEMENT 

Placement procedures for all implant systems re- 
quire atraumatic preparation of the recipient site. 
Thermal injury to bone is minimized by using a 
low-speed, high-torque handpiece, along with copi- 
ous irrigation. The irrigation is either externally or 
internally applied and directed through channels in 
the drill. Manufacturer recommendations relating 
to the type of irrigation and speed of the drilling 
equipment should be followed. Threaded implants 
often require final thread preparation in the bone at 
very low speeds. 

The implant recipient site is prepared with a series 
of gradually enlarged burs. All implant systems have 
an initial small- diameter drill used to mark the im- 
plant site. The implant site is located using the surgi- 
cal template, which may also assist in directing angu- 
lation of the implant. The center of the implant 
recipient site is marked with the initial drill, and a pi- 
lot hole is prepared. A paralleling pin is then placed in 
the preparation to check alignment and angulation. 
At this point, a final determination is made re- 
garding the adequacy of the recipient site for im- 
plant placement. Although implant placement is a 
surgical procedure, it is influenced by critical 
restorative parameters. The stent communicates the 
range of acceptable implant positions and angula- 
tions. At this step, if it is apparent that supporting 
bone will not allow proper positioning of the im- 
plant, further osseous augmentation may be neces- 
sary, either simultaneously with implant placement, 
or as a separate procedure with implant placement 
delayed until proper osseous support is available. 
After the desired depth and diameter of the 
recipient site are achieved, the implant is placed. 
For titanium implants, an uncontaminated sur- 
face oxide layer is required for osseointegration. 
Hydroxyapatite-coated implants are also sensitive 
to contamination. 

Nonthreaded implants are positioned in the re- 
cipient site and gently tapped into place with a mal- 
let and seating instrument. Threaded implants are 
screwed into place, which also requires cutting the 
screw threads in the recipient site. Self-tapping im- 
plants are available for use in the maxilla, where the 
bone is soft enough to make prethreading unneces- 
sary. After all implants are placed, tension-free clo- 
sure prevents wound dehiscence. 



I 



Section 2 Clinical Procedures -Part I 



POSTOPERATIVE EVALUATION 

A radiograph should be taken postoperatively to 
evaluate the position of the implant in relation 
to adjacent structures (e.g., the sinus and the inferior 
alveolar canal) and other implants. Any significant 
problems noticed at this time should be corrected. 
Patients are given mild analgesics and 0.12% 
chlorhexidine gluconate rinses for 2 weeks after 
surgery to keep bacterial populations to a minimum 
during healing. Weekly evaluations are recom- 
mended until soft tissue heahng is complete (2 to 3 
weeks). If possible, complete or removable partial 
dentures should not be worn for 1 week after 
surgery. The resin over the implant can then be re- 
duced by 2.0 or 3.0 mm and replaced with a soft 
liner, so that the denture can be worn without injur- 
ing the healing implant site. 

IMPLANT UNCOVERING 

If a two-stage system is used, implant uncovering is 
performed after complete implant fixture integra- 
tion has been achieved. The time interval for inte- 
gration to occur varies and depends on the particu- 
lar site and patient. Longer times may be required if 
the bone quality and surgery were less than ideal or 
if the bone-to-implant interface was questionable at 
the time of placement. In general, recommended in- 
tegration times are 6 months in the maxilla, 3 
months in the anterior mandible, and 4 months in 
the posterior mandible. 

The goals of surgical uncovering are to accurately 
attach the abutment to the implant, to preserve at- 
tached tissue, and to recontour tissue as necessary. 
These goals may be accomplished with any of these 
three techniques: the tissue punch, crestal incision, 
or flap repositioning. 

After the implant is exposed, the implant abut- 
ment is placed. There are two approaches for this 
procedure. The first approach is to place the same 
abutment as will be used in the restoration. The sec- 
ond approach is to place a temporary healing cap 
that will remain until the tissue heals and will then 
be replaced by the abutment during the surgical 
treatment procedures. 

When the abutment is placed, the superstructure 
must be completely seated on the implant body 
without gaps or intervening tissue. In systems with 
antirotational facets in the implant (see Fig. 13-17), 
these features must be aligned to allow complete seat- 
ing of the abutment. The superstructure-implant 
body interface should be evaluated radiographically 
immediately after the uncovering. If a gap is present, 
the superstructure must be repositioned. 



IMPLANT RESTORATIONS 

Osseointegrated implants are generally designed to 
support screw- or cement-retained implant restora- 
tions. These implant systems offer many advan- 
tages over conventional dental restorations and 
one- stage implants (Box 13-3). 

Fabrication of screw-retained implant restora- 
tions requires a number of components unique to 
implant dentistry. For less experienced clinicians, 
the large number of parts included within one sys- 
tem might create problems. This section describes in 
generic terms the component parts typically needed 
to restore an osseointegrated implant. There are 
many implant systems, and although all the major 
components are available for each system, many 
differ slightly in specific design and materials. The 
basic steps for implant restoration fabrication are 
described in Figure 13-19. 

CLINICAL IMPLANT COMPONENTS 
Terms used to describe similar implant components 
vary widely among manufacturing companies. A 
hst of terms used in this book and a partial Ust of al- 
ternative terms are described in Box 13-4. 

Implant Body. The implant body is the compo- 
nent placed within the bone during first- stage 
surgery. It may be a threaded or nonthreaded root 
form and is normally made of either titanium or ti- 
tanium alloy of varying surface roughnesses, with 
or without a hydroxyapatite coating (Fig. 13-20). Al- 
though some controversy exists regarding the opti- 
mum shape and surface coating for an implant in 
different parts of the mouth, the significant factors 
for success are precise placement, atraumatic 
surgery, unloaded healing, and passive restoration. 



Advantages of Osseointegrated 
Implants box 13-3 



1 . Surgicd 

a. Documented success rote 

b. fr>-off«ce procedure 

c. Adaptable to multiple intraoral locations 

d. Precise implont site preporotion 

e. Reversibility in the event of implant failure 

2. Prostfietic 

c, Multiple restorative op Hon s 

b. Versotihty of second-stage components 

• Angle correction 

• Estfietics 

• Crown contours 

• Screw- or cement- retained optiorts 

c. Retrievability in the event of prosthodontic failure 



Chapter 13 Implant- Supported Fixed Prostheses 



I 




Fig. 13-19. A, Healing caps in place 2 weeks after second-stage surgery. A two-unit implant prosthesis 
will be fabricated distal to the conventional crown on the mandibular second premolar. B, Two abutments 
are selected to thread into the implants when the healing caps are removed. C, The abutments are placed 
intraorally, and the premolar is prepared for a conventional crown. D, The impression posts are tightened 
onto the abutments, and a displacement cord is placed only around the conventional preparation. E, After 
an impression is made, the impression posts are removed from the mouth and attached to the laboratory 
analogs. F, Impression posts and analogs are relocated in the impression before pouring. G, The impres- 
sion posts locate the analogs in the same position on the cast as the abutments are in the mouth. H, Im- 
pression posts removed from the analogs. Waxing sleeves are attached, and a full-contour waxing is com- 
pleted and cut back. I, The unit is then cast, incorporating the waxing sleeves in the prosthesis, and is 
fitted back on the cast. J, Porcelain is applied to the prosthesis, which is secured by retaining screws coun- 
tersunk below the occlusal surface. K, The completed prosthesis replaces the mandibular first and second 
molars. Composite resin covers the screw access holes. The prosthesis is not joined to the conventional 
crown on the mandibular second premolar. L, Radiograph of the completed restorations. 



I 



Section 2 Clinical Procedures-Part I 



Implant Terminology 



BOX 13-4 



Ti\/ IlKM 

Implant body 

(see Fig. 13-20) 
Cover screw 
(see Fig. 13-21) 

Healing obuhnent 
(see Fig. 13-22) 



Healing cop 
(see Fig. 13-22, B) 

Standard abutmenf 
(see Fig. 13-23 A) 



Tapered abutment 
(see Fig. 13-23,8) 



Hkx driver 

[see Fig. 13-32,0 



Abutment driver 
or seaHng tool 

Impression post 
(see Fig. 1 3-32, A 6, D) 



Laboratory analog 
(see Fig. 13-32, G) 



Temporary 
abutment sleeve 
{seeFig. 13-49, H) 

Fixed abutment 
(see Fig. 13-23, S, Q 



Plastic sleeve 
(see Fig. 1 3-36) 



Gold cylinder 

(see Fig. 13-37) 

(waxing sleeve) 
Prosriiesis- 

retaining screw 
Fostening screw 

(see Fig. 13-40) 



Af ^o KNtnw \s 
tmpldnl fixture &crew 

Cylinder 
Sealing screw 
Healing screw 
First stoge cover screw 
Temporary gingival 

cuff 
Healing collar 
Implant healing cop 
Temporary screw 
Comfort cap 
Abutment healing cap 
Tfonsmucosal 

obutment 
Tissue extension 
Permucosal extension 
Conical abutment 
Tronsmucosol 

abutment 
Tissue extension 
Permucosal abutment 
Hex tool 
Screwdriver 



Name of each 

driver/tool is specific 
based on its use 

Impression coping 

Impression pin 

Transfer pin 

Transfer post 

Implont fixed anolog 

Abutment onolog 

Implont body analog 

Fixture replica 

Temporary cylinder 

Temporary coping 

Provisional abutment 

Straight abutment 

Coping abutment 

Abutment post 

Crown and bridge 
obutment (stong) 

Plastic sheoth 

Waxing sleeve 

Plastic coping 

Castabfe abutment 

Castoble coping 

Gold sJeeve 

Gold coping 

Gold screw 

Coping screw 
Fastening screw 



1 I M 111 >\ 

Portion of the implont system within the bone 



Seals the occlusal surface of the implant during osseointegration 



A cover, attoched to the implant, that is used to maintain tfie open- 
ing through the tissue until the restoration is completed 



A cover thot is attached to the top of a tronsmucosa! abutment, pro- 
tecting the internal threads and interfoce surfaces of the 
abutment 

An intermediate component placed between the implant and metal 
fromework/restofotion, providing support and retention for a 
fixed -removable restorotion, Excellent for bar overdentures 

An intermediote component ploced between the implant and 
restoration, providing support and retention for a fixed-remov- 
able restoration. The abutment is cone shaped for maximum es- 
thetics. Excellent for screw-retained fixed prostheses. 

Used for placing and removing oil hex screws (i.e., abutment fas- 
tening screws), impression post-retaining screws, and healing 
abutments. Available in two lengths: Short (19 mm - for poste- 
rior) and long (24 mm - for anterior); and three hex sizes; 
0.048", 0.050", and 0.062" 

Used to seat the abutment direcHy onto the implant 



Component used during the impression procedure to transfer the 
position of tire implant to the cast 



Replicates the implant for use in tfie cast 



Provides support and retention for ocryltc temporary/provisional 
restorations. May also be used for occlusal rim and wok set'Up 
try-in procedures for overdentures. 

An abutment used for o cement retained restoration 

(Also available in 15" and 25'' angles) 



A castoble plastic pattern used to form an abufment during ifie lab- 
oratory waxing procedure 



A premochined abutment that is waxed ond cast to. It interfaces di- 
rectly onto the tronsmucosol abutment. 

Screw used to secure a screw-retained metal (bar) framework or 
restoration to tronsmucosol abutments (i.e., conical or stondard 
abutments) 



Chapter 13 Implant- Supported Fixe d Prostheses 



I 







d 



Fig. 1 3-20. Four main categories of osseointegrated im- 
plants. Left to right: titanium screw, hydroxyapatite-coated 
screw, hydroxyapatite-coated cylinder, titanium 
plasma-sprayed cylinder. 




Fig. 1 3-21 . Cover screw in place during the initial 
implant- healing phase. Soft tissue is sutured over the im- 
plant. A removable prosthesis can be worn over this area 
during healing. 

All contemporary dental implants have an inter- 
nally threaded portion that can accept second- stage 
screw placements. These implants also may incor- 
porate an antirotational feature within the design of 
the fixture body. If it is incorporated, the antirota- 
tional feature may be either internal or external. 

Implant bodies can also be classified as one stage 
or two stage. Onc-stage implants project through the 
soft tissue immediately after Stage I surgery. Two- 
stage implants are typically covered with soft tissue 
at this point. When a tall cover screw or healing cap 
is placed on a tw^o-stage implant to project it 
through the tissue at the time of placement, this is 
referred to as "using a two-stage implant with a 
one-stage protocol." 

Cover Screw. During the healing phase follow- 
ing first- stage surgery, a screw is normally placed in 
the superior aspect of the fixture. It is usually low in 
profile to facilitate the suturing of soft tissue in the 
two- stage implant or to minimize loading in the one- 
stage implant (Fig. 13-21). At second-stage surgery, it 
is removed and replaced by subsequent compo- 
nents. In some systems the screw is made slightly 




Fig. 13-22. Two types of healing abutments. Both allow 
for soft tissue healing after second-stage surgery. A, This 
type screws into the implant. B, This type screws into the 
abutment. It is more commonly referred to as a healing cap. 

larger than the diameter of the implant, which facil- 
itates abutment placement by ensuring that bone 
does not grow over the edge of the implant. The im- 
plant surgeon should always be sure that the sealing 
screw is completely seated after stage-one surgery to 
prevent bone from growing between the screw and 
the implant. If this occurs, removing the bone may 
damage the superior surface of the implant and af- 
fect the fit of subsequent components. 

Healing Abutment. Healing abutments are 

dome-shaped screws placed after second-stage 
surgery and before insertion of the prosthesis. They 
range in length from 2 to 10 mm and project 
through the soft tissue into the oral cavity. They 
may screw directly into the fixture or, in some sys- 
tems, onto the abutment immediately after second- 
stage surgery. Those that screw onto the abutment 
are commonly referred to as healing caps (Fig. 13-22). 
Both healing abutments are made of titanium or ti- 
tanium alloy. In areas where esthetics is paramount, 
healing should be sufficiently completed around a 
healing cap to stabiUze the gingival margin. At this 
time, abutments of appropriate length are selected 



I 



Section 2 Clinical Procedures -Part I 



to ensure that the metal-porcelain interface of 
the restoration will be located subgingivally. In 
areas where tissue esthetics is not critical, adequate 
healing for impressions usually takes 2 weeks. In es- 
thetic zones, 3 to 5 weeks may be required before 
abutment selection. In addition, knowing the 
length of the healing cap can expedite abutment 
selection. 

Abutments. Abutments are the component of 
the implant system that screw directly into the im- 
plant. They will eventually support the prosthesis 
in screw-retained restorations, since they accept the 
retaining screw of the prosthesis. For cement- 
retained restorations, they may be shaped like a 



conventional crown preparation. Abutments take 
many forms (Fig. 13-23). Their walls are usually 
smooth, polished, and straight- sided titanium or ti- 
tanium alloy. Their length ranges from 1 to 10 mm. 
In nonesthetic areas, 1 to 2 mm of titanium should 
be allowed to penetrate the soft tissue to maximize 
the patient's ability to clean the prosthesis (Fig. 
13-24). In esthetic areas, an abutment can be selected 
to allow porcelain to be carried subgingivally for 
optimum esthetics (Fig. 13-25). 

In implant systems that incorporate an antirota- 
tional feature, the abutment must have two compo- 
nents that move independently of each other-one 
engages the antirotational feature, and the other se- 
cures the abutment within the fixture (Fig. 13-26). 



Abutments 




01}:%^' 



" O 'q t*^ 



1* 








.# 
.%"? 



(screwj 



Fixed 
Itemcnitjd) 



Angled 

{cemeni or 

screw) 



Tiipered 
(screw) 



NonscKmented 

or UCIA 

(screw) 



Fig. 1 3-23. Types of abutments {\eU tO right): A, Standard. Length can be selected to make the margin 
subgingival or supergingival. B, Fixed. This abutment is much like a conventional post-and-core. It is 
screwed into the implants, has a prepared finish line, and receives a cemented restoration. C, Angled. 
This type is available when implant angles must be corrected for esthetic or biomechanical reasons. 

D, Tapered. This type can be used to make the transition to restoration more gradual in larger teeth. 

E, Nonsegmented, or direct. This type is used in areas of limited interarch distance or areas where es- 
thetics is important. The restoration can be built directly on the implant, so there is no intervening abut- 
ment. This direct restoration technique has been called the UCLA abutment. 

(Modified from Peterson etai: Contemporary oral surgery, ed3, St Louis, 1998, Mosby.) 




Fig. 1 3-24. A, Healing abutments projecting through the soft tissue. B, Implant restorations sup- 
ported by standard abutments that allow easy access for oral hygiene. 



Chapter 13 Implant- Supported Fixed Prostheses 



I 




Fig. 13-25. A, Healing abutments projecting through the tissue for implant restoration of maxillary 
central incisors. B, Fixed abutments selected with margins 1 to 2 mm subgingival. C, Completed, ce- 
mented restorations. D, Overall esthetic result. 



C3 




Fig. 13-26. When an antirotational feature is to be engaged by the 
abutment, one component of the abutment (the sleeve) must fit the hexa- 
gon whereas the other (the screw) independently tightens the compo- 
nents together. 




Section 2 Clinical Procedures-Part I 



Angled abutments use a similar technique to correct 
divergently placed implants (Figs. 13-27 and 13-28). 
Some systems have recently included tapered or 
wide-base abutments, which allow teeth with larger 
cross-sectional diameters to be restored with more 
physiologic contours. The nonsegmented implant 



crown (UCLA) bypasses the abutment portion by us- 
ing a sleeve waxed directly to the implant. Using 
nonsegmented implant crowns may be necessary 
when soft tissue thickness is less than 2 mm. All-ce- 
ramic components designed to be tightened directly 
to the implant also have been introduced (Fig. 13-29). 






1^ 



4 




\ 



Fig. 1 3-27. A, This implant in the maxillary lateral incisor position is angled too far facially to restore 
with a straight abutment. B, An abutment angled 15 degrees with subgingival margins is screwed to 
place. C, The completed crown cemented onto the angled abutment. A provisional luting agent can be 
used to maintain retrievability, although choosing a suitable material that retains the restoration ade- 
quately but can still be removed is not always easy. 




Fig. 13-28. A, Severely angled implants require 25-degree angled abutments. B, Completed restora- 
tion on 25-degree angled abutments with retaining screws redirected toward the occlusal surface. 




Fig. 1 3-29. A, An all-ceramic abutment designed to fit directly against the implant is compatible with 
aluminous dental porcelain. B, A screw-retained, all-ceramic restoration can be used on larger teeth and 
has excellent esthetics. 
(Courtesy Drs. A. Ingber and V. Prestipino.) 



Chapter 13 Implnnt-Siipporterl Fixed Prostheses 



I 



The choice of abutment size will depend on the 
vertical distance between the fixture base and op- 
posing dentition, the existing sulcular depth, and 
the esthetic requirements in the area being restored. 
For acceptable appearance, fixtures in the posterior 
maxilla or mandible may require margin termina- 
tion at or below the gingival crest. An anterior max- 
illary crown may require 2 to 3 mm of subgingival 
porcelain at the facial gingival margin to create the 
proper emergence profile and appearance. Frame- 
work fit should be checked on multiple unit restora- 
tions if abutment margins are no more than 1 mm 
subgingivally. Periodontal probing of the sulcus af- 
ter the healing cap is removed will reveal the space 



available for subgingival extension and can be per- 
formed at the time of abutment placement or fol- 
lowing a period of tissue healing around a provi- 
sional restoration. When these measurements have 
been made, the correct abutment is attached to the 
implant. The abutment length can have a dramatic 
effect on restoration contours (Fig. 13-30). 

Impression Posts. Impression posts facilitate 
transfer of the intraoral location of the implant or 
abutment to a similar position on the laboratory 
cast. They may screw into the implant or onto the 
abutment and are customarily subdivided into fix- 
ture types or abutment types (Fig. 13-31). 



A 





^. 



Fig. 1 3-30. A, Two crowns fabricated for the same lingually tipped mandibular implant. The arrows 
denote the connection to the implant body for both units. Crown 2 is fabricated on a 4-mm abutment. 
Crown 1 is connected directly to the implant body, allowing the creation of more physiologic contours. 
B, One-year follow-up of crown 1. The soft tissue response is excellent despite a poorly placed implant. 




Fig. 1 3-31 . Types of impression posts. A, A one-piece (screws onto abutment) is used if the abutment 
does not need to be changed on the laboratory cast. B, A one-piece (transfer) is attached directly to the 
fixture if the abutment does need to be changed on the cast (it should have a flat side if angle correction 
will be necessary). C, A two-piece (pick-up), used to orient the antirotational feature or to make impres- 
sions of very divergent implants. 



I 



Section 2 Clinical Procedures-Part I 



With the transfer impression post in place, an im- 
pression is made intraorally. Both of these can be 
further subdivided into transfer types (indirect) and 
pick-up (direct) types after radiographs are taken to 
confirm complete engagement. Heavier-body im- 
pression materials (e.g., poly[vinyl siloxane] and 
polyether) are usually recommended, although any 
conventional impression material can be used. 
When the impression is removed from the mouth, 
the impression post remains in place on the implant 
abutment or on the fixture. It is then removed from 
the mouth and joined to the laboratory analog be- 



fore being transferred to the impression in the 
proper orientation. If the clinician anticipates that 
the implant angulation will have to be corrected on 
the laboratory cast, a flat-sided impression post that 
goes directly into the fixture or implant should be 
used (Fig. 13-32). The flat side of the post will accu- 
rately orient the location of the implant and position 
the threads and the antirotational feature. When an 
angled abutment is placed or screwed into the im- 
plant, it must be oriented in the same position as the 
prosthesis was fabricated in the laboratory. Com- 
pletely symmetric impression posts are contraindi- 



A,B 



D,E 



G,H 



J,K 




Fig. 1 3-32. A^ A standard transfer impression post is a sleeve that matches the implant diameter. A 
screw penetrates through its center. B, The screw can be placed through the impression post sleeve and 
carried to the mouth with the standard hex driver (C). D, Impression post seated into the implant. 
E, Radiograph confirming complete seating. F, Complete impression, clearly showing flat sides. G, Labo- 
ratory analog corresponding to the size of the implant. H, Impression post removed from the mouth and 
attached to a laboratory analog. 1, Impression post/analog complex inserted into the impression with 
flat sides properly oriented. J, Polyether impression material injected around the complex before pour- 
ing. K and L, Impression post orients the laboratory analog to cast as the implant body is positioned in 
the mouth. 



Chapter 13 Tmpbnt-Snppnrted Fixed Prostheses 



I 



cated if angle correction may be necessary. If the 
chnician decides to transfer the orientation of an an- 
tirotational feature from the mouth to the laboratory 
model, the two-piece pick-up (direct) impression 
technique should be used. This technique requires a 
two-piece impression post with a removable guide 
pin that screws directly into the abutment or onto 
the fixture. It uses a square coping with a long guide 
pin and usually an open-top tray. The impression 
coping is designed with square side walls to pre- 
vent rotation in the impression material. An 
open-top impression tray allows access to the guide 
pin for unscrewing after the material has set so that 
the copings can be picked up within the impression 
when removed from the mouth (Fig. 13-33). When 
implants are oriented at significantly divergent an- 
gles, the pick-up technique is generally considered 
to be the more accurate of the two procedures. The 
transfer technique is more convenient and some- 
times mandatory when space is limited and screw- 
driver access would be limited. Before an implant 
impression is taken, a radiograph should be made 



A 




Fig. 1 3-33. A, Cross-sectional view of the two-piece im- 
pression post, which remains within the impression mater- 
ial. B, The impression screw passes through the coping to 
attach the laboratory analog. 



to ensure that the components are properly assem- 
bled. This requirement is especially important when 
an antirotational feature is involved. 

Laboratory Analogs. Laboratory analogs are 
made to represent exactly the top of the implant fix- 
ture or the abutment in the laboratory cast. There- 
fore, they can be classified as fixture analogs and 
abutment analogs (Fig. 13-34). Both types screw di- 
rectly into the impression post after it has been re- 
moved from the mouth, and the joined components 
are returned to the impression before pouring. The 
final impression should be poured in either dental 
stone or die stone. The gingival tissues can be re- 
produced by injecting an elastomer (e.g., Perma- 
dyne*) to represent soft tissue around the laboratory 
analog before pouring. This will facilitate removal 
of the impression post from the stone cast and the 
placement of subsequent abutments without break- 
ing the stone and losing the reference point of the 
soft tissue (Fig. 13-35). 

Abutment analogs are generally attached to an 
implant impression post. Implant body impression 
posts are normally attached to implant body 
analogs. The advantage of using the implant body 
analog is that the abutments can be changed in the 
laboratory. Also, if a flat- sided impression post has 
been used to orient the threads or the hexagon of 
the implant body analog properly, the decision to 
correct the implant angulation can be deferred until 
the laboratory stage. If the clinician is confident that 
the appropriate abutment has been selected, using 
the abutment impression post and abutment ana- 
log can simplify the procedure. If a supragingival 



*ESPE-North America: Norristown, Pa. 








Fig. 13-34. Laboratory analogs. These represent either 
implants or abutments. A duplicates the top of the implant. 
B duplicates the top of the abutment. 



I 



Section 2 Clinical Procedures-Part I 




Hg . 13-35. A and B, Polyether impression material injected around a laboratory analog before the 
Impression is poured. The gingival material should not cover any retention features of the analog. C, The 
Impression material reproduces the patient's soft tissue contours adjacent to the implant. The impression 
post may be removed and other components inserted without losing the associated anatomic landmarks. 
D, Completed restoration. 
(Courtesy Dr. C. Pechous.) 



■■^^ 


l^p 


•^* 


^HpF^ 




r4 ^^ 




i ^:' 



Fig. 13-36. Plastic waxing sleeve tightened to a labora- 
tory analog. 




Fig. 13-37. 
analog. 



Gold cylinder tightened to a laboratory 



abutment margin has been selected, a soft tissue 
cast will not be necessary. 

Waxing Sleeves. Waxing sleeves are attached to 
the abutment by the relating screw on the labora- 
tory model. They will eventually become part of the 
prosthesis. In nonsegmented implant crowns, they 
are attached directly to the implant body analog in 
the cast. 

Commonly referred to as UCLA abutments, they 
may be plastic patterns that will be burned out and 
cast as part of the restoration framework (Fig. 
13-36), precious metal that will be incorporated in 



the framework when it is cast to the precious alloy 
cylinder, or a combination of each (Fig. 13-37). Us- 
ing a metal waxing sleeve ensures that two ma- 
chined surfaces will always be in contact. The cast 
surface of the plastic waxing sleeve may be retooled 
before it is returned to the fixture. 

Waxing sleeves are available in several vertical 
dimensions. Tall ones can be shortened to conform 
to the requirements of the occlusal plane. Today, 
most waxing sleeves are a combination of gold alloy 
and plastic (Fig. 13-38). This combination allows the 
machined fit of the alloy at the implant, with the 
cost advantage of plastic at the waxing surface. 



ChaptenlS Implant-Supported Fixed Prostheses 



I 




Fig. 13-38 . A, Waxing sleeves with gold alloy base and plastic extension. B, On the laboratory cast, 
the technician can wax to the plastic extension. The wax and plastic will be burned out, and the new al- 
loy will be "cast to" the original alloy base. 





Fig. 13-39 . Two types of prosthesis-retaining screws. 
A, Nonsegmented crown retained to implant. B, Crown re- 
tained on abutment. 



Prosthesis-retaining Screws. Prosthesis-retain- 
ing screws penetrate the fixed restoration and se- 
cure it to the abutment (Fig. 13-39). They are tight- 
ened with a screwdriver and attach nonsegmented 
crowns to the body of the implant. They generally 
are made of titanium, titanium alloy, or gold alloy 
and may be long (which allows them to penetrate 
the total length of the implant crown) or short 
(which requires countersinking them into the oc- 
clusal surface of the restoration). Screws that are 
countersunk must be covered by an initial layer of 
resilient material (e.g., gutta-percha, cotton, or sih- 
cone). A subsequent seal of composite resin is 
placed over the resilient plug (Fig. 13-40). 

IMPLANT RESTORATIVE OPTIONS 

Distal-extension Implant Restoration. Implant 
support offers major advantages in the treatment of 
partially edentulous patients in whom no terminal 
abutment is available. In this situation, the conven- 
tional dental treatment plan would include a re- 




Fig. 13-40. A, Prosthesis-retaining screws countersunk 
below the occlusal surface of the restoration. B, Composite 
resin placed in screw access holes after the retaining screws 
are tightened. 



movable partial denture. However, with the im- 
plant alternative, patients can avoid the discomfort 
and inconvenience of a removable prosthesis. 

There are two distal-extension restorative op- 
tions. One option is to place an implant distal to the 
most posterior natural abutment and fabricate a 
fixed prosthesis connecting the implant with the 
natural tooth. However, there are problems associ- 
ated with implants connected to natural teeth (see 
p. 356). The other option is to place two or more im- 
plants posterior to the most distal natural tooth and 
fabricate a completely implant- supported restora- 
tion (Fig. 13-41). If the crown-to-implant ratio is fa- 
vorable, two implants to support a three-unit fixed 
partial denture may be considered. If implants are 
short and crowns are long, one implant to replace 



I 



Section 2 Clinical Procedures -Part I 



A 




Fig. 1 3-41 . A^ Two implants placed distal to the mandibular canine. B, The completed restoration is 
not connected to the natural tooth. 





Fig. 13-42. a. Natural tooth prepared between two im- 
plants. B, Telescopic coping permanently cemented onto 
the natural tooth. C, Prosthesis placed with screw retention 
on the implants and temporary cement retention on the 
telescopic coping. 

each missing tooth is highly recommended. If doubt 
remains, more implants are used when heavier 
forces are expected (e.g., the posterior part of the 
mouth in patients with evidence of parafunctional 



activity). Fewer implants are used when lighter 

forces are expected (e.g., those opposing a complete 
denture or those supporting a prosthesis in the an- 
terior part of the mouth). 

Long Edentulous Span Restoration. Similar 
options can be used when treating a long edentu- 
lous span. The clinician may choose to have multi- 
ple implants placed between the remaining natural 
teeth and to fabricate a fully implant- supported 
restoration. As an alternative, one or two implants 
can be placed in the long edentulous span and the 
final restoration connected to natural teeth. When it 
is necessary to connect implants and the natural 
teeth, protecting the teeth with telescopic copings is 
recommended (Fig. 13-42). In this manner, prosthe- 
sis retrievability can be maintained. In addition, 
some long edentulous spans require the reconstruc- 
tion of soft and hard tissue as well as teeth. In these 
instances, using resin teeth processed to a metal 
substructure rather than a conventional metal- 
ceramic restoration is recommended. Soft tissue es- 
thetics can be more easily and accurately mimicked 
with heat-processed resin and large defects (Fig. 
13-43). This type of restoration has been called a hy- 
brid because it combines the principles of conven- 
tional fixed and removable prosthodontics. For 
smaller defects, pink porcelain can be used to com- 
pensate for missing soft tissue (see Fig. 13-24, B). 

Single-tooth Implant Restoration. The use of 

single implants in restoring missing teeth is an at- 
tractive option for the patient and the dentist. How- 
ever, it requires careful implant placement and 
precise control of all prosthetic components. Sin- 
gle-tooth restorations supported by implants may 
be indicated in the following situations: 

1. An otherwise intact dentition 

2. A dentition with spaces that would be more 
difficult to treat with conventional fixed 
prosthodontics 



rhnpter n Tmplnnt-Snpported Fixed Prostheses 



I 




Fig. 13-43. A, Large mandibular defect created by a shotgun wound. B, Metal substructure of a hy- 
brid prosthesis tried onto three implants in this defect. C, Denture resin can more effectively recreate the 
soft tissue color and contours in the completed restoration than dental porcelain. D, Hybrid restoration 
restoring the defect. 



3. Distally missing teeth when cantilevers or re- 
movable partial dentures are not indicated 

4. A prosthesis that needs to closely mimic the 
missing natural tooth 

The requirements for single-tooth implant crowns 
are as follows: 

1. Esthetics 

2. Antirotation-to avoid prosthetic component 
loosening 

3. Simplicity-to minimize the amount of compo- 
nents used 

4. Accessibility-to maintain optimum oral health 

5. Variability-to allow the clinician to control the 
height, diameter, and angulation of the implant 
restoration 

Several systems have been developed to comply 
with these demands. Common indications include 
congenitally missing maxillary lateral incisors (Fig. 
13-44) and teeth in which endodontic treatment was 
unsuccessful (Fig. 13-45). Screw loosening has most 
commonly been associated with the terminally po- 
sitioned single molar implant crown (Fig. 13-46). 

Matching the soft tissue contours of adjacent nat- 
ural teeth remains the most difficult challenge for 
completing the anterior single-tooth restoration. 
These contours can be reliably created with provi- 
sional restorations. One technique, which combines 
soft tissue contouring and provisional placement, is 




Fig. 13-44. A, Lateral incisor crowns attached to im- 
plant abutments. B, Single tooth implant crowns replacing 
the maxillary lateral incisors. 

shown in Figure 13-47. When the tissue has matured 
around the provisional restoration, a final impres- 
sion can be taken to complete the definitive restora- 
tion (Fig. 13-48). Impressions can also be made at 



I 



Section 2 Clinical Procedures-Part I 




Fig. 1 3-45. A, Occlusal view of a single tooth implant crown replacing a fractured mandibular pre- 
molar. B, Buccal view of a single- tooth implant crown replacing a mandibular premolar. 



Fig. 13-46. Screw loosening is most commonly associated with 
single-tooth molar implant crowns. 




A,B 



D,E 




Fig. 1 3-47. A^ Soft tissue healing 2 weeks after second-stage surgery and placement of a healing cap. 
B, The healing cap removed. Note that the interdental papilla has been preserved. An impression post 
may be placed, and an implant master cast prepared. C, Soft tissue cast prepared with a laboratory bur 
to create the ideal soft tissue architecture. D, A gold waxing sleeve attached to the laboratory analog re- 
tains the provisional restoration. E, A full-contour wax pattern can be used to fabricate the provisional. 
F, Duplicate cast of the full-contour wax pattern. Continued 



I 



G,H 




Fig. 13-47, COnt d. q^ a^ acrylic template is adapted to the duplicate cast and returned to the mas- 

ter cast. H, Waxing posts to create a screw access hole in the provisional restoration. I, A provisional im- 
plant restoration is fabricated by one of the techniques described in Chapter 15. J, The soft tissue is con- 
toured to accept a provisional restoration. A diamond curettage bur can be used when sufficient attached 
tissue is present. K, Soft tissue contouring improves esthetics, minimizes pocket depths, and allows 
more physiologic restoration contours. L, The provisional restoration. Soft tissue is allowed to heal for 
4 to 6 weeks before the final impression is made. 



the time of Stage I surgery so that a provisional can 
be delivered at Stage II to facilitate more ideal soft 
tissue contours (Fig. 13-49). The best soft tissue es- 
thetics are still generally achieved when interdental 
papillae are present before the surgery. If soft tissue 
contours are deficient before surgery, the patient 
should expect some compromise in the final soft tis- 
sue result. 

Fixed Restoration in the Completely Edentulous 
Arch. For completely edentulous patients who 
require nonremovable restorations, there are two 
implant options: a hybrid prosthesis and a fixed 
metal-ceramic rehabilitation (Figs. 13-50 to 13-52). 

The hybrid prosthesis is a cast alloy framework 
with processed denture resin and teeth. It requires a 
minimum of five implants in the mandible and six 
in the maxilla. One major determining factor for se- 
lecting this option is the amount of bone and soft 
tissue lost. For patients who have had moderate 
bone loss, the prosthesis restores both bone and soft 
tissue contours. 

The metal- ceramic rehabilitation also requires 
five implants in the mandible and six in the maxilla. 
It can be made esthetically pleasing only if minimal 



bone loss has occurred and is best suited for pa- 
tients who have recently lost their natural teeth 
(within 5 years). For patients with severe bone loss, 
there is probably only one option: a removable 
restoration (Fig. 13-53). 

The main advantage of a completely fixed 
restoration, whether it is hybrid or metal-ceramic, is 
that it is completely retained by the patient at all 
times. Therefore, patients experience the psycho- 
logic benefit of having a restoration that closely re- 
sembles their original natural teeth. In addition, 
movement within the system is minimized, and the 
components tend to wear out less quickly. Because 
the prosthesis is screw retained, the dentist can re- 
move it, allowing access for cleaning and repairs. A 
potential disadvantage is that the implants must be 
precisely placed, especially in the maxillary anterior 
esthetic zone. Implants placed in embrasure spaces 
can lead to disastrous esthetic results and can im- 
pede access for hygiene. With a hybrid prosthesis, 
the clinician must decide between leaving enough 
space for hygiene access and minimizing space for 
optimum esthetics. Some patients may be con- 
cerned by the amount of metal shown in a hybrid 
prosthesis. However, from a conversational distance. 



I 



Section 2 Clinical Procedures-Part I 





Fig. 1 3-48. a. Soft tissue around a maxillary implant provisional restoration after 6 weeks of healing. 
B, New soft tissue contours compared to the healing abutment previously in place. C, Final impression 
made and a master cast fabricated. The new soft tissue contours are reproduced. D, Implant crown 
placed on the maxillary right central incisor. E, Preservation of the interdental papilla is important for 
patients with medium to high smile lines. F, One-year follow-up showing that the patient has main- 
tained healthy soft tissue contours. 

(Courtesy Dr. J. Hollow ay .) 



rh^pter n Tmpln nt-Siipporterl Fixed Prostheses 



I 



A,B 



D,E 



G,H 



J,K 




Fig. 13-49. Stage It provisional technique. A, Patient missing maxillary right central incisor. B, Surgi- 
cal template in position. C, Once the screw-shaped implant is in place, the fixture mount is luted to the 
surgical template with resin before it is unscrewed from the mouth. D, Analog attached to the fixture 
mount. E, Diagnostic stone cast prepared to position analog. F, Template placed back on diagnostic cast. 
G, Dental stone is flowed around the analog. The position of the analog is identical to the position of the 
implant in the mouth. H to L, A plastic sleeve is used for the fabrication of a provisional restoration that 
can be delivered at Stage 1 1 surgery. 



I 



Section 2 Clinical Procedures-Part I 




Fig. 1 3-50. A metal-ceramic implant restoration may be 
indicated if adequate bone and soft tissue contours are 
available. 




Fig. 1 3-51 . Hybrid restorations are the treatment of 
choice for edentulous patients with moderate bone 
resorption. 




Fig. 13-52. Radiograph sho^ving fixed restorations sup- 
ported by six implants in the maxilla and five in the 
mandible. 

a properly made prosthesis will be hardly notice- 
able. Esthetic and phonetic problems in the maxil- 
lary arch can often be avoided by not placing im- 
plants near the midline and restoring the incisor 
teeth with pontics. This approach to implant place- 
ment improves the restorative outcome consider- 
ably (Fig. 13-54). 



lent-planning 
implant options for 
edentuiouis patients 
depend on bone 
resorption, 






Fig. 1 3-53. The amount of bone resorption dictates the 
treatment options for an edentulous patient. A, Minimal re- 
sorption may allow metal-ceramic restorations. B, Moder- 
ate resorption may necessitate resin-to-metal (hybrid) 
restorations. C, Severe resorption will require only implant- 
supported overdentures for optimum esthetic results. 



CEMENT-RETAINED VERSUS SCREW-RETAINED 
IMPLANT CROWNS 

Cemented implant crowns can be luted to a 
screw-retained abutment. Zinc phosphate, glass 
ionomer, and composite resin cements have all been 
suggested for this purpose. However, retrievability 
of the implant restoration is ordinarily not consid- 
ered when a permanent cement is used. The provi- 
sional cements have been recommended because 
they allow restoration retrieval. However, unpre- 



rhapter 1 1 Tm plnnt-Siipporterl Fixed Prostheses 



I 




Fig. 13-54. A, A surgical template can be fabricated for an edentulous patient by duplicating the ex- 
isting denture in clear resin. B, The lingual aspect of the template is removed, leaving the most facial 
2 mm of resin intact. The surgeon will have access to the bone, but it will be confined to the arch form. 
C, The ideal positions for maxillary implants are the canine, second premolar, and second molar areas. 
Cross arch implant parallelism is also important. D, Access for hygiene must be allowed around implant 
abutments. E, If implants are located posterior to the canine, access for hygiene can be created without 
compromising esthetics or phonetics. F, Reasonable esthetics and phonetics can be accomplished with a 
hybrid restoration if modified ridge-lap pontics are used in the maxillary central and lateral incisor 
positions. 



dictability of the temporary luting agents can lead 
to a difficult retrieval or premature displacement. 

Simplicity and, in some systems, economy are the 
major advantages of cement-retained restorations. 
In addition, cementing allows minor angle correc- 
tions to compensate for discrepancies between the 
implant inclination and the facial crown contour 
(Fig. 13-55). Resistance to rotation is particularly 
critical with cemented prosthetics, and the abut- 
ment should then incorporate an antirotational fea- 
ture. Very small teeth are most easily replaced with 
cement-retained implant crowns (Fig. 13-56). 

One misconception about cement-retained 
crowns is that they are simpler and have fewer 
screw-loosening episodes. They actually require 
more chair time and have the same propensity to 



loosen. They are, however, more esthetically pleas- 
ing and less expensive. 

The screw-retained implant crown is fastened 
either to the abutment or directly to the implant. 
The main advantage of this restoration is its retriev- 
ability. Retrievability allows for crown removal, 
which can facilitate soft tissue evaluation, calculus 
debridement, and any other necessary modifica- 
tions. In addition, future treatment considerations 
can be made more easily and are less costly if the 
implant restoration is retrievable. However, in 
screw -retained restorations, the access hole must be 
through the occlusal table of posterior teeth or 
the lingual surface of anterior teeth. Forces can then 
be directed in the long axis of the implant, and 
optimum esthetics is more easily achieved. This 



I 



Section 2 Clinical Procedures-Part I 




Fig. 13-55. A, Implant in position to replace 
central incisor. B, A laboratory cast demonstrates 
facial angulation of the implant. C, An angled 
abutment allows esthetic restoration (D). 




B r-^ 




-^Vlv--; 



Fig. 1 3-56. A, Very small teeth are difficult to restore es- 
thetically with screw-retained restorations. B, Occlusal view 
of screw-retained mandibular central incisors. Note the dis- 
crepancy in incisal edge widths caused by the screw access 
holes. 




Fig. 1 3-57. Torque on the screw develops a preload 
(clamping force) between the implant and the crown. 



requirement dictates an ideal surgical location, 
which is not always possible because of anatomic 
limitations. The primary disadvantage of a 
screw-retained implant restoration is that the screw 
may loosen during function. Many techniques for 
retaining screw connection have been reported. The 
direct mechanical interlock or antirotational feature 
appears to be the most effective. 



If the screw is sufficiently tightened into the im- 
plant crown to seat it, a clamping load or preload is 
developed between the implant and the crown (Fig. 
13-57). If this clamping force is greater than the 
forces trying to separate the joint between implant 
and crown, the screw will not loosen. An implant 
screw should be tightened with sufficient force to 
seat the crown, but not so much as to affect the 



rhapter n Trnpl ant- Supported Fixed Prostheses 



I 



Screw loosening can 
be a problem with 
implant prostheses. 




Fig. 13-58. The screw will loosen only if the joint- 
separating force is greater than the clamping force. 



LOOSE Implant Screws 



BOX 13-5 



CHliCK: 

1. Excessive occlusal contacts not in tKe long axis of the 
implant 

2. Excessive cantilever contacts 
3* Excessive lateroi contacts 

4, Excessive interproximal contacts 

5. Inat^equately tightened screws 



bone-implant interface. Torque wrenches are avail- 
able to achieve this. In addition, lateral forces 
(which tend to separate the joint) should be elimi- 
nated or reduced (Fig. 13-58 and Box 13-5.) 

BIOMECHANICAL FACTORS 
AFFECTING LONG-TERM 
IMPLANT SUCCESS 

OCCLUSION (Box 13-6) 

Bone resorption around dental implants can be 
caused by premature loading or repeated overload- 
ing. Vertical or angular bone loss is usually charac- 
teristic of bone resorption caused by occlusal 
trauma. When pressure from traumatic occlusion is 
concentrated, bone resorption occurs by osteoclastic 
activity. In the natural dentition, bone remodeling 
typically occurs once the severe stress concentration 



Implant Occlusion 



BOX 13-6 



1 * Direct forces in long axis of the implant. 

2. Minimize lateroi forces on the implant. 

3» Ploce lateral forces when necessary as far anterior in 
the arch as possible. 

4. When it is impossible to minimize or move lateral forces 
anteriorly, distribute themi over as many teeth and im- 
plants OS possible. 



is reduced or eliminated. However, in the osseointe- 
grated implant system, after bone resorbs, it usually 
does not reform. Because dental implants most ef- 
fectively resist forces directed primarily in their long 
axis, lateral forces on implants should be minimized. 

Lateral forces in the posterior part of the mouth 
are greater and more destructive than lateral forces 
in the anterior part of the mouth. When they cannot 
be completely eliminated from the implant prosthe- 
sis, efforts should be made to distribute them 
equally over as many teeth as possible. 

Implant restorations should be designed to mini- 
mize damaging forces at the implant-bone interface, 
with particular attention to the occlusion. Flatter in- 
clines can be developed on implant cusps, creating 
more vertical resultant forces and a shorter moment 
arm (Fig. 13-59). Whenever possible, a cusp-fossa 
relationship should be established in the intercuspal 
position with no eccentric occlusal contacts (see 
Chapter 18). The maxillary single-tooth restoration 
is vulnerable to screw loosening due to occlusal 
contacts, which usually produce an inchned resul- 
tant force with increased torque on the retaining 
screw. Optimum implant orientation will effectively 
reduce these forces. 

In general, the location and inclination of force 
should be seriously considered in the restorative 
phase of implant treatment. Divergent implant 
placement increases the moment arm through which 
force is transmitted to the bone-implant interface; 
this could exceed the threshold for bone resorption. 
Interchangeable components to alter implant angles 
have been produced by implant body manufactur- 
ers. However, it has been shown that increasing 
abutment angles also produces increased stresses at 
the bone-implant interface. Angled abutments may 
solve immediate esthetic or contour problems while 
masking potential long-term consequences created 
by an implant placement that is poorly planned or 
dictated by the patient's anatomy. 

Inadequate implant distribution may also lead to 
excessive cantilevers or forces that could potentiate 
overloading of implant bodies. Whenever possible, 
dental implants should be joined so that forces may 
be more equally distributed over multiple implants. 



I 



Section 2 Clinical Procedures-Part I 



A carefully designed 
ocdusion is critical to 
implant success. 




Fig. 1 3-59. sharper cusp inclines and wider occlusal ta- 
bles increase the resultant force on implant components. 



Ideally, one implant for every tooth to be restored 
should be placed. This number is particularly im- 
portant when shorter implants are placed in 
poorer- quality bone. When implants longer than 13 
mm can be placed in dense bone, two for every three 
teeth being replaced are acceptable. Full arch restora- 
tions should not be considered on less than six im- 
plants in the maxilla and five in the mandible. Im- 
plant cantilevers should be kept as short as possible. 
However, cantilevering considerable distances off 
five well-integrated fixtures in the anterior mandible 
is possible. Quite often, cantilevering to the first mo- 
lar is possible. Equations based on the distribution 
and length of fixtures have been proposed." 

CONNECTING IMPLANTS TO NATURAL TEETH 
It has been suggested" that connecting a single os- 
seointegrated implant to one natural tooth with a 
fixed partial denture can create excessive forces be- 
cause of the relative immobility of the osseointe- 
grated implant compared to the functional mobility 
of a natural tooth. During function, the tooth moves 
within the limits of its periodontal ligament, which 
can create stress at the neck of the implant up to two 
times the implied load on the prosthesis (Fig. 13-60). 
Potential problems with this type of restoration in- 
clude (1) breakdown of the osseointegration, (2) ce- 
ment failure on the natural abutment, (3) screw or 
abutment loosening, and (4) failure of the implant 
prosthetic component. This situation is encountered 
clinically when the most posterior abutment is lost 
in the dental arch and a fixed prosthesis is needed to 
connect a single implant to the natural tooth. If pos- 
sible, a totally implant- supported fixed partial den- 




Fig. 1 3-60. When a single implant is attached to a nat- 
ural tooth, biting forces on the natural tooth and pontic 
cause stress to be concentrated at the superior portion of 
the implant. 




Fig. 1 3-61 . A semi-precision attachment may compen- 
sate for vertical displacement forces in the tooth and an 
implant-supported fixed prosthesis. It does not compensate 
for forces in the buccolingual direction. 
(Courtesy Dr. G. Seal.) 

ture with two or more implants should be provided. 
However, anatomic limitations of the maxillary si- 
nus or the mandibular canal often limit restorative 
efforts directed at a single fixture site. 

When connecting an implant to a natural tooth is 
necessary, multiple implant or natural tooth abut- 
ments should be used. A semi-precision attachment 
(keyway) in the prosthesis between the implant and 
the natural tooth may solve potential problems ^^ (Fig. 
13-61). However, under most circumstances, when a 
load is applied to the pontic, the additional move- 
ment at the attachment actually increases the can- 
tilever effect on the implant abutment. In practice, 
the only advantage of a semi-precision attachment 
may be that it allows a screw-retained implant abut- 
ment crown to be removed for periodic evaluation. 



Chapter 13 Implant- Supported Fixed Prostheses 



I 




Fig. 1 3-62. A, Metal try-in for maxillary rehabilitation using implant abutments and a telescopic cop- 
ing on the maxillary left premolar. B, Prosthesis screw retained on implants with temporary luting agent 
over the telescopic coping. 




Fig. 13-63. Metal framework fit should be evaluated 
with only a single retaining screw in place. 



When circumstances dictate using a natural tooth 
abutment, a telescopic coping should be considered. 
This is permanently cemented to the natural tooth 
and can prevent decay if loosening occurs. Provi- 
sional cement is used to attach the prosthesis to the 
coping. If it leaches out of the implant crown, the 
natural tooth will still be protected (Fig. 13-62). 

IMPLANT AND FRAMEWORK FIT 

Pathogenic forces can be placed on an implant if the 
framework does not fit passively. When all the pros- 
thesis-retaining screws are tightened, gaps between 
the abutment and a poorly fitting framework will 
close, giving the appearance of an acceptable fit. 
However, significant compressive forces are placed 
on the interfacial bone, which can lead to implant 
failure. The fit of all implant frameworks should be 
checked with only one screw in place. No visible 
amounts of space or any amounts of movement 
with finger pressure should be discernible on any of 
the other implant abutments (Fig. 13-63). If a non- 
passively fitting framework is identified, it should 
be sectioned and soldered and then reassessed for 
passive fit. A relation record should also be made. 



SHOCK-ABSORBING ELEMENTS 

Because there is no movement between the bone and 
an osseointegrated implant, incorporating some 
type of shock- absorbing layer to reduce occlusal im- 
pact forces may be necessary. One theory claims that 
such forces may exceed the threshold necessary for 
bone resorption to occur. This shock absorber could 
be specially designed into the implant system, or the 
occlusal surface of the restoration might be con- 
structed of acrylic resin to accomplish the same ef 
feet. These recommendations are based on theoreti- 
cal calculations rather than on clinical data, and the 
need for shock- absorbing elements remains a con- 
troversial subject in implant dentistry. 

^] MAINTENANCE 

The goal of implant maintenance is to eradicate mi- 
crobial populations affecting the prosthesis. Al- 
though dental implants may be more resistant than 
natural teeth to the effects of bacterial plaque, this 
has yet to be definitively proved. Until more re- 
search is available, proper and timely home care 
measures for prolonging the lifetime of an implant 
are most effective. Clinicians must ensure that the 
patient receives thorough instruction in mainte- 
nance techniques, including an initial session with 
the clinician. This should be reinforced by a training 
session with the dental hygienist during a recall 
visit. Recall visits should be scheduled at least every 
3 months during the first year. The patient's oral hy- 
giene should be evaluated and documented at a re- 
call visit; reinstruction should be provided when 
necessary. Sulcular debridement must be perfomed 
with plastic or wooden scalers, since conventional 
instruments will scratch the titanium. Implant abut- 
ments may be polished using rubber cups with a 
low- abrasive polishing paste or tin oxide. 



I 



Section 2 Clinical Procedures-Part I 



At each recall appointment, implant mobility 
should be evaluated; any bleeding after probing 
should be examined. Framework fit and occlusion 
also must be checked. Attention to both biologic and 
biomechanical factors is important to the long-term 
success of dental implants. 

COMPLICATIONS 

BONE LOSS 

The primary complication with dental implant ther- 
apy is bone loss around the implant (Fig. 13-64). 
Any loss exceeding 0.2 mm per year is cause for 
concern. Multiple factors are associated with im- 
plant bone loss: 

1. Inappropriate size and shape of the implant 

2. Inadequate number of implants or implant 
positioning 

3. Poor quality or inadequate amount of avail- 
able bone 

4. Initial instability of the implant 

5. Compromised healing phase 

6. Inadequate fit of the prosthesis 

7. Improper design of the prosthesis (e.g., ex- 
cessive cantilever, poor access for hygiene) 

8. Excessive occlusal forces 

9. Deficient fit of abutment components (i.e., 
gaps that allow bacterial colonization) 

10. Inadequate oral hygiene 

11. Systemic influence (e.g., tobacco use, 
diabetes) 

The restorative dentist should pay particular at- 
tention to the fit of the prosthesis, the access for hy- 
giene, and the presence of excessive occlusal forces. 
If bone loss reaches 25% to 30%, revision surgery 
should be considered. 

PROSTHETIC FAILURE 

Additional implant prosthetic complications in- 
clude fracture of the implant components or the 




prosthesis. Fracture of implant components is usu- 
ally attributed to fatigue from biomechanical over- 
load (Fig. 13-65). Failure of the implant prosthesis is 
usually traceable to less than ideal laboratory pro- 
cedures or prosthesis design (Figs. 13-66 and 13-67). 

SUMMARY 

Implant- supported prostheses, using cylindrical os- 
seointegrated fixtures placed by a two-stage surgi- 
cal technique, should be considered in the treatment 
of any partially edentulous patient. They are a reli- 
able solution to many situations that are difficult to 
treat by conventional measures: the patient who 




Fig. 1 3-65. Fractured abutment screw on a tooth and 
implant-supported prosthesis. 




Fig. 1 3-66. Porcelain fracture on an implant prosthesis 
with inadequate metal support. 




Fig. 1 3-64. To monitor implant bone loss, radiographs 
should be evaluated once a year. 



Fig. 1 3-67. Resin fracture on a hybrid prosthesis. The 
prosthesis can be retrieved easily for repair. 



cannot wear removable appliances, the patient with 
a long edentulous span or other circumstance (e.g., 
short roots) that diminishes the prognosis for an 
FPD, and the patient ^vith a single missing tooth but 
sound adjacent teeth. 

Success with implant prosthodontics requires the 
same attention to detail and careful planning as con- 
ventional fixed prosthodontics. Often a team ap- 
proach is recommended, with a surgeon placing the 
implant and a restorative dentist designing the 
prosthesis. The critical stage is optimum placement 
of the implant(s). The surgeon's main concern is 
that it be well within the available bone and away 
from vital structures (e.g., the inferior dental canal). 
The restorative dentist's main concern is that the 
positioning and angulation of each fixture allo^v op- 
timum occlusion, esthetics, and tissue health as well 
as minimum stresses at the implant-bone interface. 
Information obtained from a clinical examination, 
radiographs, and a diagnostic waxing on articulated 
casts is crucial to planning. Surgery is guided by a 
template made from the diagnostic waxing. 

Depending on the implant site, a two- stage surgi- 
cal technique requires 3 to 6 months for bone to heal 
against the implant. In a second surgery, the implant 
is uncovered and implant abutments are screwed 
into place. Subsequently, a screw-retained prosthesis 
is fabricated to restore function and appearance. 

Several implant systems are available, each with 
a variety of components for restorative manage- 
ment (e.g., an antirotational feature incorporated in 
an implant for single tooth replacement). 

Problems unique to implant prosthodontics in- 
clude screw loosening and bone loss from prema- 
ture loading or repeated overloading. Occlusal con- 
siderations, prosthesis fit, plaque control, and 
follow-up care are all primary concerns to the pro- 
fessionals who deal with implants and convention- 
ally supported prostheses. 



Chapter 13 Implant-Supported Fixed Prostheses 

awssNfm 



I 




dental implant: a prosthetic device of alloplastic mate- 
rial implanted into the oral tissues beneath the mu- 
cosal or/and periosteal layer, and/or within the 
bone to provide retention and support for a fixed or 
removable prosthesis; a substance that is placed 
into or/and upon the jaw bone to support a fixed or 
removable prosthesis-usage: although dental im- 
plants may be classified by their silhouette or geo- 
metrical form (i.e., fin, screw, cylinder, blade, bas- 
ket, rootform, etc.) generally, dental implants are 
classified based on their anchorage component as it 
relates to the alveolar bone that provides support 
and stabihty. Thus, there are epo steal dental implants, 
endosteal dental implants, and transo steal dental im- 
plants. Some dental implants possess both eposteal 
and endosteal components (by design or subse- 
quent anchorage change); the decision as to what 
anchorage system provides the most support at ini- 
tial placement determines which category is used to 
best describe the dental implant. 

endosteal dental implant: a device placed into the alve- 
olar and/or basal bone of the mandible or maxilla 
and transecting only one cortical plate. The en- 
dosteal dental implant is composed of an anchor- 
age component, the dental implant body, which, 
ideally, is within the bone, and a retentive compo- 
nent(s), the dental implant abutment, which connects 
to the implant body, passes through the oral mu- 
cosa, and serves to support and/ or retain the pros- 
thesis. Such an abutment may be for interim or 
definitive application-usage: interim abutment, de- 
finitive abutment. Descriptions of the implant body 
that use silhouette or geometric forms, such as 
cylinder, blade, basket, or endodontic, may be used 
as adjectives to enhance understanding of the 
geometry of any endosteal dental implant. Interim 
or definitive abutments may be composed of one or 
more elements. The abutment elements usually are 



'^dif QjA^^iiofit 



1. Discuss fhe history and scientiFic basts for osseointegration. 

2. Dtscuss the indications and contraindications For inripJ ant-supported fixed partial dentures, 

3. When treatment-pfanning the replacement of a congenitolly missing lateral incisor with an impbnt restora- 
tion, describe the necessary mtnimum bone dimensions vertically, horizontolly, and between roots, Also 
describe the guidelines used lo position the implant in the appropriate anteroposterior and superoinFertor 
location. 

4, Describe the technique used to replicate the intraoral location of on implant on the laboratory cast. 

5, list and describe the various types of abutments used for implant restorations. When is each type recom- 
mended? Why? 

6, Describe some common problems with implont restorations ond recommend methods to manage them. 



I 



Section 2 Clinical Procedures-Part 



described by means of their geometric form, i.e., 
screw, coping, cylinder, lug. 

hybriCl prOSthSSiS: slang: a nonspecific term for any 
prosthesis that does not follow conventional design. 
Frequently it is used to describe a prosthesis that is 
composed of different materials, types of denture 
teeth (porcelain, plastic, composite), variable acrylic 
denture resins, differing metals, etc. It may refer to 
a fixed partial denture or any removable prosthesis. 

'implant: V (1890): to graft or insert a material such as 
an alloplastic substance, an encapsulated drug, or 
tissue into the body of a recipient. 

implant: n (1809): any object or material, such as an 
alloplastic substance or other tissue, which is par- 
tially or completely inserted or grafted into the 
body for therapeutic, diagnostic, prosthetic, or ex- 
perimental purposes. 

implant abutment: the portion of a dental implant that 
serves to support and/or retain any prosthesis- 
usage: frequently dental implant abutments, espe- 
cially those used with endosteal dental implants, 
are changed to alter abutment design or use before 
a definitive prosthesis is fabricated. Such a prelimi- 
nary abutment is termed an interim abutment. The 
abutment chosen to support the definitive prosthe- 
sis is termed a definitive abutment. 

implant body: the portion of a dental implant that pro- 
vides support for the abutment(s) through adapta- 
tion upon (eposteal), within (endosteal), or through 
(transosteal) the alveolar bone-usage: eposteal 
dental implants alveolar bone support system has, 
heretofore, been termed the implant frame, implant 
framework, or implant substructure, however, this is an 
integral component of that dental implant and is not 
subservient to any other component. 

implant prOSthodontiCS: the phase of prosthodontlcs 
concerning the replacement of missing teeth and/or 
associated structures by restorations that are at- 
tached to dental implants. 

implant substructure: the metal framework of a 
eposteal dental implant that is embedded beneath 
the soft tissues, in contact with the bone, and stabi- 
lized by means of endosteal screws. The periosteal 
tissues retain the framework to the bone. The frame- 
work supports the prosthesis, frequently by means 
of abutments and other superstructure components. 

implant surgery: (I993): the phase of implant dentistry 
concerning the selection, planning, and placement 
of the implant body and abutment. 

implantOlOQy obs: a term historically conceived as the 
study or science of placing and restoring dental im- 
plants. 

osseous: adj (1707): bony. 

osseous integration: (I993) l: the apparent direct at- 
tachment or connection of osseous tissue to an inert, 
alloplastic material without intervening connective 
tissue 2: the process and resultant apparent direct 



connection of an exogeous material's surface and 
the host bone tissues, without intervening fibrous 
connective tissue present 3: the interface between 
alloplastic materials and living tissue. 

perJ-JmplantitiS: in periodontics, a term used to de- 
scribe inflammation around a dental implant, usu- 
ally its abutment. 

transosteal dental implant: l: a dental implant that pen- 
etrates both cortical plates and passes through the 
full thickness of the alveolar bone 2: a dental implant 
composed of a metal plate with retentive pins to 
hold it against the inferior border of the mandible 
that supports transosteal pins that penetrate 
through the full thickness of the mandible and pass 
into the mouth in the parasymphyseal region- 
called also staple bone plant, mandibular staple implant, 
transmandibular implant. 

1. NIH Consensus Development Conference: State- 
ment on dental implants, J Dent Educ 52:824,1988. 

2. Adell R et al: A 15-year study of osseointegrated 
implants in the treatment of the edentulous jaw, 
Int J Oral Surg 10:387, 1981. 

3. Kent J et al: Biointegrated hydroxylapatite- 
coated dental implants: 5-year clinical observa- 
tions, J Am Dent Assoc 121:138, 1990. 

4. Lazzara RJ et al: A prospective multicenter study 
evaluating loading of osseotite implants two 
months after placement: one-year results, J Es- 
thetDent 10:280, 1998. 

5. Buser D et al: Removal torque values of titanium 
implants in the maxillofacial of miniature pigs, 
Int J Oral Maxillofac Implant 13:61 1, 1998. 

6. Smithloff M, Fritz ME: Use of blade implants in 
a selected population of partially edentulous pa- 
tients, /PenoJonto/ 53:413, 1982. 

7. Kapur KK: VA cooperative dental implant study: 
comparisons between fixed partial dentures sup- 
ported by blade-vent implants and removable 
partial dentures. 11. Comparisons of success rates 
and periodontal health between two treatment 
modalities, J Pro sthet Dent 62:685, 1989. 

8. Smith D, Zarb GA: Criteria for success for os- 
seointegrated endosseous implants, J Prosthet 
Dent 62:567, 1989. 

9. McGlumphy EA, Larsen PE: Contemporary im- 
plant dentistry. In Peterson LJ et al, editors: Con- 
temporary oral and maxillofacial surgery, ed 3, 

St Louis, 1998, Mosby. 

10. Hobo S et al, editors: Osseointegrated and occlusal 
rehabilitation, Tokyo, 1990, Quintessence 
Publishing. 

11. Chiche Gl, Pinault A: Considerations for fabrica- 
tion of implant- supported posterior restorations, 
IntJProsthod 4:37, 1991. 



rhapter H Trnplant-Siipported Fixed Prostheses 



I 



12. Clelland N, Gilat A: The effect of abutment an- 
gulation on the stress transfer for an implant, 
JProstliod 1:24, 1992. 

13. Takayama H: Biomechanical considerations on 
osseointegrated implants. In Hobo S et al, edi- 
tors: Osseointegrated and occlusal rehabilitation, 
Tokyo, 1990, Quintessence Publishing. 



14. Sullivan D: Prosthetic considerations for the uti- 
lization of osseointegrated fixtures in the par- 
tially edentulous arch, Int J Oral Maxillofac Im- 
plants 1:39, 1986. 



CHAPTER 



FOURTEEN 



Tissue Management and 
Impression making 



accelerator 

custom impression tray 

dimensional stability 

elastomer 

hydrocolloid 

impression 

impression material 



i schemia 

monomer 

polyether 

polysulfide 

reversible hydrocolloid 

tissue displacement 



Because it is neither possible nor desirable to make 
patterns for fixed prostheses directly in the mouth, 
an impression, or negative likeness of the teeth and 
surrounding structures, is necessary to obtain a cast. 
This cast is then used to make a restoration in the 
laboratory. To obtain the cast, an elastic impression 
material is placed in a tray that is inserted into the 
patient's mouth. When the material has set, it is re- 
moved from the mouth. A suitable dental stone is 
then poured into the "negative" impression, and a 
positive likeness or working cast is obtained. 

An acceptable impression must be an exact 
record of all aspects of the prepared tooth. This 
means it must include sufficient unprepared tooth 
structure immediately adjacent to the margins for 
the dentist and laboratory technician to identify the 
contour of the tooth and all prepared surfaces. The 
contour of the unprepared tooth structure cervical 
to the preparation margin is critical information that 
must be available when the restoration is fabricated 
in the dental laboratory. If the impression does not 
reproduce this critical area where tooth and future 
restoration meet, fabricating the restoration with 
proper contours is not possible (barring some lucky 
guesswork). 

All teeth in the arch and the soft tissues immedi- 
ately surrounding the tooth preparation must be re- 
produced in the impression. They will allow the cast 
to be accurately articulated and will contribute to 
proper contouring of the planned restoration. Par- 
ticular attention is given to reproducing the lingual 
surfaces of anterior teeth because they influence an- 
terior guidance, which determines the occlusal mor- 



phology of the posterior teeth (see Chapter 4). The 
impression must be free of air bubbles, tears, thin 
spots, and other imperfections that might produce 
inaccuracies. 

The patient's mouth is a challenging environ- 
ment in which to make an accurate impression. 
Moisture control is probably one of the most impor- 
tant aspects of successful impression making. Ex- 
cept for the polyethers, all elastomeric impression 
materials are hydrophobic' (i.e., they do not tolerate 
or displace moisture). Any moisture will result in 
voids. Consequently, saliva flow into the area must 
be reduced and diverted to obtain the necessary dry 
field of operation. 

When the preparation margins extend subgingi- 
vally, the adjacent gingival tissues must be dis- 
placed laterally to allow access and to provide ade- 
quate thickness of the impression material. This 
may require enlarging the gingival sulcus through 
mechanical, chemical, or surgical means and must 
be done without jeopardizing periodontal health. 
Improper manipulation of impression material and 
tissue displacement can lead to permanent soft tis- 
sue damage. 

PREREQUISITES 

TISSUE HEALTH 

After the teeth are prepared and a provisional 
restoration has been made (see Chapter 15), the 
health of the surrounding soft tissues must be 
reevaluated. Careful preparation will result in min- 
imal tissue damage; however, if a subgingival mar- 
gin is needed, some tissue trauma in the sulcular 
area may be unavoidable. The effects of this trauma 
can be transient as long as the patient receives a 
properly made provisional restoration and main- 
tains adequate oral hygiene. However, if the provi- 
sional is poorly contoured, not polished, or has de- 
fective margins, plaque retention will lead to a 
localized inflammatory response. The combination 
of such tissue trauma in the presence of preexisting 
periodontal disease can produce disastrous results. 



354 



rh^pter 1 4 Tissue Mnnngement nnd Impression Making 



I 



Periodontal disease must be treated and resolved 
before fixed prostheses are placed. 

On occasion, a defective restoration will con- 
tribute to the inflammatory sulcular response. If this 
is the case, a properly adapted and well-contoured 
polished provisional must be fabricated and ce- 
mented on the prepared teeth; the focus must shift 
from the teeth to the soft tissues, which must be re- 



turned to a state of optimum health before impres- 
sion making is even considered. 

SALIVA CONTROL 

Depending on the location of the preparations in the 
dental arch, several techniques can be used to create 
the necessary dry field of operation (Fig. 14-1). In ar- 
eas where only supragingival margins are present. 




Fig. 14- 1 . Saliva control for impression making. When correctly placed, maxillary cotton rolls block 
salivary flow from the parotid gland. A, The evacuator removes saliva from the floor of the mouth, keep- 
ing the prepared tooth dry while the flange displaces the tongue medially. B, Svedopter and Speejector 
saliva evacuators. C, Placement of the Svedopter with cotton rolls. D, An absorbent card. E, The dispos- 
able Hygoformic aspirator system. F, Denta Pops aspirator system. 
(E courtesy Sullivan-Schein Dental.) 



I 



Section 2 Clinical Procedures -Part I 



moisture control with a rubber dam is probably the 
most appropriate method. However, in most in- 
stances a rubber dam cannot be used, and absorbent 
cotton rolls must be placed at the source of the 
saliva; an evacuator must be placed where the 
saliva pools. In the maxillary arch, placing a single 
cotton roll in the vestibule immediately buccal to 
the preparation and a saliva evacuator in the op- 
posing lingual sulcus is usually sufficient. When 
working on a maxillary second or third molar, mul- 
tiple cotton rolls must sometimes be placed imme- 
diately buccal to the preparation and slightly ante- 
rior to block off the parotid duct, which opens just 
anterior to the maxillary first molar. If a maxillary 
roll does not stay in position but slips down, it can 
be retained with a finger or the mouth mirror. When 
making a mandibular impression, placing addi- 
tional cotton rolls to block off the sublingual and 
submandibular salivary ducts is usually necessary. 
Rolls on the buccal and Ungual sides of the prepared 
teeth will help with soft tissue retraction-the cot- 
ton on the buccal side displaces the cheek laterally, 
and the cotton on the lingual side displaces the 
tongue medially. One or two cotton rolls placed ver- 
tically between the horizontally placed cotton rolls 
in the buccal vestibules will help maintain the latter 
in position. 

An alternative to multiple cotton rolls is place- 
ment of one long roll "horseshoe fashion" in the 
maxillary and mandibular mucobuccal folds. How- 
ever, when part of the cotton is saturated, the entire 
roll must be replaced. The use of moisture- absorb- 
ing cards (see Fig. 14-1, D) is another method for 
controlling saliva flow. These cards are pressed- 
paper wafers covered with a reflective foil on one 
side. The paper side is placed against the dried buc- 
cal tissue and adheres to it. In addition, two cotton 
rolls should be placed in the maxillary and 
mandibular vestibules to control saliva and displace 
the cheek laterally. 

The tongue can be a problem when working in 
the mandibular arch. Saliva evacuators may help 
eliminate excess flow, but most of these are dis- 
placed easily by a "probing" tongue. If lingually 
placed cotton rolls continually become dislodged or, 
in conjunction with a conventional saliva evacuator, 
fail to control moisture adequately, a flanged-type 
evacuator (e.g., the Svedopter* or the Speejectort) 
should be considered (see Fig. 14-1, B). To avoid the 
risk of soft tissue trauma, this device must be placed 
carefully. A cotton roll between the blade and the 



*EC Moore Co,: Dearborn, Mich. 

tPulpdent Corporation of America: Brookline, Mass. 



mylohyoid ridge of the alveolar process will mini- 
mize intraoral patient discomfort. Simultaneously, if 
properly positioned, this type of device will provide 
a "stop" that prevents the flange from being dis- 
placed farther buccally, allowing excellent lingual 
access to mandibular posterior teeth. Care must be 
taken not to tighten the chin clamp excessively, be- 
cause considerable discomfort can result from pres- 
sure to the floor of the mouth. A disposable saliva 
ejector designed to displace the tongue may also be 
effective (see Fig 14-1, E and F). 

In addition to the pain control normally needed 
during tissue displacement, local anesthesia may 
help considerably with saliva control during impres- 
sion making. Nerve impulses from the periodontal 
ligament form part of the mechanism that regulates 
saliva flow; when these are blocked by the anes- 
thetic, saliva production is considerably reduced. 

When saliva control is especially difficult, a 
medication with antisialagogic action may be con- 
sidered. Dry mouth is a side effect of certain anti- 
cholinergics 2,3 (drugs that inhibit parasympathetic 
innervation and thereby reduce secretions, including 
saliva). This group of drugs includes atropine, 
dicyclomine, and methantheline. Anticholinergics 
should be prescribed with caution in older adults 
and should not be used in any patient with heart dis- 
ease. They are also contraindicated in individuals 
with glaucoma, because they can cause permanent 
blindness. The incidence of undiagnosed glaucoma 
in the general population is high, and some physi- 
cians recommend that all patients be evaluated oph- 
thalmologically before antichohnergics are used. 

Clonidine,4 an antihypertensive drug, has success- 
fully reduced salivary output. It is considered safer 
than anticholinergics and has no specified con- 
traindications. However, it should be used cautiously 
in patients who take hypertension medication. In a 
clinical trials 0.2 mg of clonidine reduced salivary 
flow as effectively as 50 mg of methanthehne. 

DISPLACEMENT OF GINGIVAL TISSUES 
Tissue displacement is commonly needed to obtain 
adequate access to the prepared tooth to expose all 
necessary surfaces, both prepared and not pre- 
pared. This is most effectively achieved by place- 
ment of a displacement cord (generally impreg- 
nated with a chemical agent). Sometimes gingival 
tissue is excised with a scalpel or with electro- 
surgery. 

Displacement Cord. Some enlargement of the 
gingival sulcus can be obtained by placing a nonim- 
pregnated cord and leaving it in place for a sufficient 
length of time. The cord is pushed into the sulcus and 



Chapter 14 Tissue Management and Impression Making 



I 



mechanically stretches the circumferential periodon- 
tal fibers. Placement is often easier if a braided (e.g., 
Gingibraid)* or a knitted (e.g., Ultrapak) cord is 
used. However, larger sizes of braided cord should 
be avoided because they have a tendency to "double 
up" and can become too thick for atraumatic intra- 
sulcular placement. In areas where very narrow sulci 
preclude placement of the smaUer sizes of twisted or 
braided cord, wool-like cords that can be flattened 
are preferable for initial displacement of tissue. 

Better sulcus enlargement can be achieved with a 
chemically impregnated cord or by dipping the cord 
in an astringent (e.g., Hemodent). These materials 
contain aluminum or iron salts and cause a transient 
ischemia, shrinking the gingival tissue. Even so, the 
sulcus closes quickly (less than 30 seconds) after the 
cord is removed; therefore, the impression must be 
taken immediately. In addition, medicaments help 
control seepage of gingival fluid. Aluminum chlo- 
ride (AICI3) and ferric sulfate (Fe2(S04)3) are suitable 
because they cause minimal tissue damage. As an 
alternative, a sympathomimetic amine-containing 
eye wash or nasal decongestant have been shown 
to be effective.' 

Many of the chemicals used for their astringent 
effect are stable only at narrow ranges of low pH 
levels. Table 14-1 shows the mean pH of some com- 
monly used materials. The low pH levels have 
raised concern about the effect of acidic solutions on 
tooth structure and, perhaps more importantly, on 
the smear layer. Figure 14-2 represents scanning 
electron micrographs of dentin after various dura- 
tions of exposure to a commonly used ferric sulfate 



*Van R Dental Products^ Inc.r Los Angeles, CaUf. 
tUltradent Products, Inc.: Salt Lake City, Utah. 
:|:ESPE-Premier: Norristown, Pa. 
§Visine (tetrahydrozohne HCl, 0.05%). 
llAfrin (oxymetazoline, 0.05%). 



solution. Contact between the astringent and the 
prepared tooth surfaces must be minimized if the 
smear layer is to be maintained. A nonacidic hemo- 
static agent can be used as an alternative. 

Several displacement cords preimpregnated with 
epinephrine are available commercially. Epineph- 
rine should be used with caution, because it may 
cause a tachycardia," particularly if it is placed on 
lacerated tissue. Dosage control is also a potential 
problem. In a recent study," clinicians were unable 
to detect any advantages of using gingival retrac- 
tion cords that were impregnated with epinephrine. 

Step-by-step Procedure 

1. Isolate the prepared teeth with cotton rolls, 
place saliva evacuators as required, and dry 
the field with air. 

2. Cut a length of cord sufficient to encircle the 
tooth (Fig. 14-3, A and B). Do not overdesic- 
cate the tooth, because this may lead to post- 
operative sensitivity. 

3. Dip the cord in astringent solution and 
squeeze out the excess with a gauze square. 
An impregnated cord can be placed dry but 
should be moistened in situ to prevent the 
thin sulcular epithelium from sticking to it 
and tearing when it is removed. 

4. If a nonbraided cord is used, twist it tightly 
for easier placement. 

5. Loop the cord around the tooth and gently 
push it into the sulcus with a suitable instru- 
ment (Fig. 14-3, C). 

It is best to start in the interproximal area (Fig. 
14-3, D), because the cord can be more easily placed 
here than facially or lingually. The instrument 
should be angled toward the tooth so the cord is 
pushed directly into the area. It should also be an- 
gled slightly toward any cord already packed; oth- 
erwise, that portion might be displaced. A second 
instrument (Fig. 14-3, E) may aid placement. 



Aciditv of Commonlv 



Astringedent 

Gingi-Aid 

Styptin 

Hemodent 

Hemogin-L 

Orostat B% 

VicoStat 

Aluminum chloride 25% 

Stasis 

For comparison: 

Ketac Dentin Etching Liquid 



Manufacturer 



Ultradent 

Gingi-Pak 

Van R 

Premier 

VanR 

Gingi-Palt 

Ultradent 

U5P 

Gingi-Pak 



Active Ingredient 



15.5% Fe-ifSOJ, 

Buffered 25% AlCia 

20% Aid, 

2L3%AlCU-6-liydrate 

A!Cl3 

8% Racemic epinephrine 

HCI 

20% Fe, (SOJ3 

25% AlCla 

Basic FejfSOjla 



Vehicle 



Aqueous 

Aqueous 

Glycol 

Glycol {aqueous) 

Aqueous 

Aqueous 

Aqueous 
Aqueous 



TABLE 14-1 



Mean pH 



0.7 
1.9 
1.3 
1.2 
0.9 
2.0 

1.6 
l.l 
0.8 

1.7 




Fig. 14-2. Disturbance of the dentinal smear layer after contact with hemostatic agents. A, Dentin 
surface prepared with a high-speed, fine-grit diamond. B, After exposure to 15.5% Fe2(S04)3 solution for 
30 seconds. The smear layer is largely removed, but many dentinal tubules are still occluded. C, After 2 
minutes of exposure. Now the smear layer is totally removed, although the peritubular dentin appears 
to be largely intact. D, After 5 minutes of exposure. Now the dentin is etched, and the peritubular dentin 
has been removed. 
(Front LandMFet ah J Prosthet Dent 72:4, 1994.) 



C,D 




Fig. 14-3. A, Cutting a section of cord of adequate length to surround the tooth. B, From left to right: 
twisted cord, braided cord, wool-like cord in various sizes. C, Most cord-packing instruments have a 
slightly rounded tip with serrations to hold the cord while positioning it intrasulcularly. D, Initial proxi- 
mal cord placement. E, An additional instrument prevents the cord from dislodging. 



Chapter 14 T issue Management and Impression Making 



■ 



NOTE: Tissue displacement must be done gently 
but with sufficient firmness to place the cord just api- 
cal to the margin. Overpacking should be avoided 
because it could cause tearing of the gingival attach- 
ment, leading to irreversible recession. Repeated use 
of displacement cord in the sulcus also should be 
avoided, since this can cause gingival recession. 

Evaluation 

Difficulty with tissue displacement is often the re- 
sult of gingival inflammation. The inflamed and 
swollen tissue bleeds easily, preventing access by 
the impression material. 

Initial assessment of cord placement can be a use- 
ful indicator of the amount of displacement accom- 
plished. When looking at the tooth preparation 
from the occlusal aspect, one should be able to see 
the preparation margin circumferentially and the 
uninterrupted cord, with no soft tissue folded over 
it, in contact with the tooth. If there is any doubt, as- 
sessing displacement by removing the cord is a 
good idea. The entire preparation margin should be 
clearly visible and will remain directly accessable 
for about a minute. 

Typically, if the resuh is acceptable, a second cord 
is quickly inserted to maintain the displacement 
while the impression material is mixed. If the sulcus 
enlargement is not favorable, the tissue health 
should be reassessed, particularly if adequate dis- 
placement cannot be obtained by repeating the pre- 
vious steps. 

Sometimes a double cord is helpful. First, a thin 
cord is placed and trimmed so that its ends do not 
overlap. A second, larger cord is then placed in the 



normal manner and removed. The thin, first cord re- 
mains during impression making. When using this 
technique, the clinician should be careful not to 
damage the epithelial attachment. 

On many occasions it is better to delay impres- 
sion making and concentrate on how to improve tis- 
sue health (e.g., by reassessing the quality of the 
provisional restoration and reinforcing oral hygiene 
instructions) rather than attempting impression 
making under adverse conditions. Minor hemor- 
rhaging can sometimes be controlled with an astrin- 
gent* or by infiltrating a local anesthetic directly 
into the adjacent gingival papillae. 

Electrosurgery. An electrosurgery unit (Fig. 
14-4, A) may be used for minor tissue removal before 
impression making. In one technique ,16 the inner ep- 
ithelial lining of the gingival sulcus is removed, thus 
improving access for a subgingival crown margin 
(Fig. 14-4, B and C) and effectively controlling post- 
surgical hemorrhage 1' (provided the tissues are not 
inflamed). Unfortunately, there is the potential for 

gingival tissue recession after treatment. 18 

An electrosurgery unit works by passage of a 
high-frequency current (1 to 4 million Hzt) through 
the tissue from a large electrode to a small one. At 
the small electrode, the current induces rapid local- 
ized polarity changes that cause cell breakdown 



*ViscoStat or Astringedent (15.5% ferric sulfate) used 
with the Dento-Infusor tips according to the recommen- 
dations of Ultradent Products, Inc., has been effective, 
tl hertz = 1 cycle/second. 




Fig. 14-4. A, An electrosurgery unit, e and c, Proce- 
dure for enlarging the gingival sulcus. 

(A courtesy Macan Engineering Co.) 



I 



Section 2 Clinical Procedures -Part I 



("cutting"). For restorative procedures, an unmodu- 
lated alternating current is recommended, because 
it will minimize damage to deeper tissues. 

The following facts should be considered before 
attempting electro surgery: 

1. It is contraindicated on or near patients with 
any electronic medical device (e.g., a cardiac 
pacemaker, TENS unit, insulin pump)" or pa 
tients with delayed healing as a result of debil- 
itating disease or radiation therapy. 

2. It is not suitable on thin attached gingivae (e.g., 
the labial tissue of maxillary canines). 

3. It should not be used with metal instruments, 
because contact could cause electric shock. (Plas- 
tic mirrors and evacuation tubes are available.) 

4. Profound soft tissue anesthesia is mandatory. 

5. A thin wire electrode is best for sulcular en- 
largement. Gingival contouring is usually per- 
formed with a loop electrode. 

6. The instrument should be set to unmodulated 
alternating current mode. 

7. The electrode should be passed rapidly 
through the tissue with a single light stroke 
and kept moving at all times. 

8. If the tip drags, the instrument is at too low a 
setting and the current should be increased. 

9. If sparking is visible in the tissue, the instru- 
ment is at too high a setting and the current 
should be decreased. 

10. A cutting stroke should not be repeated within 
5 seconds. 

1 1 . The electrode must remain free of tissue frag- 
ments. 

12. The electrode must not touch any metallic 
restoration. Contact lasting just 0.4 second has 
been shown to lead to irreversible pulpal dam- 
age in dogs 20 

13. The sulcus should be swabbed with hydrogen 
peroxide before the displacement cord is placed. 

MATERIALS SCIENCE 

James L. Sandrik 

ELASTIC IMPRESSION MATERIALS 
There is an extensive variety of materials for mak- 
ing a precision negative mold of soft and hard tis- 
sues. In order of their historical development, they 
consist of the following: 

1. Reversible hydrocoUoid 

2. Polysulfide polymer 

3. Condensation silicone 

4. Polyether 

5. Addition silicone 

Irreversible hydrocoUoid is not sufficiently accu- 
rate for cast restorations. Each material has advan- 



tages and disadvantages, and none is entirely free of 
shortcomings. However, they all share one impor- 
tant characteristic: when handled correctly, they can 
produce casts of sufficient accuracy and surface 
detail22 for the fabrication of clinically acceptable 
fixed prostheses. 

Nevertheless, there are reasons for selecting one 
material over another: If it becomes necessary to 
store the impression before a cast will be made, the 
polyethers and addition silicones are preferable be- 
cause they exhibit sufficient long-term dimensional 
stability; the other materials, particularly the re- 
versible hydrocolloids, must be poured immedi- 
ately. If the impression will be poured in epoxy or 
will be electroplated (see Chapter 17), reversible hy- 
drocoUoid should not be selected because it is com- 
patible only with die stone. 

The advantages and disadvantages of the elastic 
impression materials are summarized in Table 14-2. 

Reversible HydrocoUoid (Fig. 14-5). Reversible 
hydrocoUoid (also called agar hydrocoUoid or simply 
hydrocoUoid) was originally derived as a natural 
product of kelp. However, the material currently 
available is considerably different. 

If poured immediately, reversible hydrocoUoid 
produces casts of excellent dimensional accuracy 
and acceptable surface detail. At elevated tempera- 
tures, it changes from a gel to a sol. This change is 
reversible-i.e., as the material cools, the viscous 
fluid sol is converted to an elastic gel. Agar changes 
from gel to sol at 99° C (210° F) but remains a sol as 
low as 50° C (122° F), forming a gel only slightly 
above body temperature. These unique characteris- 
tics are very favorable for its use as an impression 
material. 

Reversible hydrocoUoid is supplied in a range of 
viscosities. Generally a heavy-bodied tray material 
is used with a less viscous syringe material. The re- 
quired temperature changes are effected with a spe- 
cial conditioning unit and water-cooled impression 
trays. 

Reversible hydrocolloid's lack of dimensional 
stability is due primarily to the ease with which wa- 
ter can be released from or absorbed by the material 
(syneresis and imbibition). The accuracy of a re- 
versible hydrocoUoid impression is improved if the 
material has as much bulk as possible (low surface 
area/volume ratio). This contrasts with the elas- 
tomeric impression materials, whose accuracy is im- 
proved by minimizing bulk (e.g., polysulfide and 
condensation silicone), because stresses produced 
during removal are reduced . 23 Therefore, an addi- 
tional advantage of reversible hydrocoUoid is that a 
custom impression tray is not required. 



Chapter 14 Tissue Management and Impression Making 



TABLE 14-2 



Irreversible 
hydrocolloid 

Reversible 
hydrocoiioid 



Po]y5uiftde polymer 



AddJtion silicone 



CondensoHon 
silicone 

Polyether 



Advantages 



Rapid set 

Straightforward technique 

Low cost 

Hydrophilic 

Long working time 

Low material cost 

No custom troy required 

tHigh tear strength 

Easier to pour than other 

elastomers 

Dimensional stability 
Pleasant to use 
Short setting time 
Automix available 



Pleasant to use 
Short setting time 

Dimensional stability 

Accuracy 

Short setting time 

Automix available 



Disadvantages 



Poor accuracy and sur- 
face detail 

Low tear resistance 
Low stability 
Equipment needed 

Messy 

Unpleosont odor 
Long setting time 
Stability only fair 
Hydrophobic 
Poor wetting 
Some materials 

release H2 
Hydrophilic formulations 

imbibe moisture 
Hydrophobic 
Poor wetting 
Low stability 
Set material very stiff 
Imbibition 
Short working time 



Recom me nded 
Uses 



Diagnostic casts 
Not suitable for 

working casts 
Multiple 

preparations 
Problems wit^ 

moisture 
Most impressions 



Most impressions 



Most impressions 



Most impressions 



Precautions 



Pour immediafely 

Pour immediately 
Use only with stone 



Pour within 1 hr; oilow 
1 min to set 



Delay pour of some 

materials 
Care to ovoid bubbles 

\fA\ef\ pouring 



Pour immediately 
Care to ovoid bubbles 

when pouring 
Care not to break teeth 

when separating cast 




Fig. 14-5. Reversible hydrocolloid impression material. A, Tray material. B, Syringe material. 

(Courtesy Sullivan-Schein Dental.) 



Poly sulfide Polymer (Fig. 14-6). The poly sul- 
fides, commonly (though erroneously) known 
as rubber bases,''' Were introduced in the early to 
middle 1950s. They were received enthusiastically 
by dentists because they had better dimensional 
stability and tear strength than hydrocolloid. Nev- 
ertheless, they should be poured as soon as possible 
after impression making; delays of more than an 
hour result in clinically significant dimensional 
change. 19 

There is a slight contraction of polysulfide during 
polymerization, but the effects can be minimized 
with a custom impression tray to reduce the bulk of 



the material. " Generally a double-mix technique is 
used with a heavy-bodied tray material and a less 
viscous syringe material. These polymerize simulta- 
neously, forming a chemical bond of adequate 
strength.25 

The high tear resistance^'" and enhanced elastic 
properties of polysulfide facilitate impression mak- 
ing in sulcular areas and pinholes, and it has im- 
proved dimensional stability over hydrocolloid (in- 
ferior to polyether and addition silicone). Although 
it is the least expensive elastomer, it is not well- 
liked by patients because of its unpleasant sulfide 
odor and long setting time in the mouth (about 10 



I 



Section 2 Clinical Procedures -Part I 




Fig. 14-6. Polysulfide polymer. 

(Courtesy Sullivan-Schein Dental.) 



minutes). Furthermore, high humidity and temper- 
ature dramatically reduce its working time '^' which 
may be so short that polymerization begins before it 
is inserted in the mouth, resulting in severe distor- 
tion). Although air conditioning is common in den- 
tal operatories, temperatures near 25 ° C (77° F) with 
humidity in excess of 60% can create problems. 
Most polysulfide materials are polymerized with 
the aid of lead peroxides, which explains this mater- 
ial's typical brown color. The unpolymerized product 
is sticky and should be handled carefully, because it 
stains clothing permanently. Alternatives to lead are 
available; copper hydroxide is the most common. 
Cu(0H)2- polymerized polysulfide is light green and 
shares many of the characteristics of the PbO 2- poly- 
merized material (except for a reduced setting time). 

Condensation Silicone (Fig. 14-7). Some of 
polysulfide's disadvantages have been overcome by 
condensation silicone, which is essentially odorless 
and can be pigmented to virtually any shade. Un- 
fortunately, its dimensional stability is less than that 
of polysulfide but greater than that of reversible hy- 
drocolloid. An additional advantage of this silicone 
is its relatively short setting time in the mouth 
(about 6 to 8 minutes). As a result, patients tend to 
prefer condensation sihcone over polysulfide. In ad- 
dition, condensation sihcone is also less affected by 
high operating room temperatures and humidity .23 

Sihcone's main disadvantage is its poor wetting 
characteristics, w^hich stems from its being ex- 
tremely hydrophobic (for this reason, it is used in 
commercial sprays that protect automobile electri- 
cal systems from moisture). In this context, the pre- 
pared teeth and gingival sulci must be completely 
free of moisture to make possible a defect-free im- 
pression. Pouring without trapping air bubbles is 
also more difficult than with other impression ma- 
terials, and a surfactant may be needed. Silicone 
impression material is available in a variety of vis- 
cosities. One technique involves a heavily filled 




Fig. 14-7. Condensation silicone. 

putty material that is used to customize a stock im- 
pression tray in the mouth, generally with a poly- 
ethylene spacer. The spacer allows room for a thin 
wash of light-bodied material, which makes the im- 
pression. The technique requires considerable care 
in seating, however, to prevent strain in the set 
putty. If this happens, the impression will rebound 
when removed from the mouth, resulting in dies 
that are too small.29 Care is also needed to avoid 
contaminating the putty surface with saliva, which 
will prevqit the wash impression from adhering 

Silicone and polysulfide have a dimensional in- 
stability that results from their mode of polymeriza- 
tion. They are both condensation polymers, which 
as a by-product of their polymerization reactions, 
give off alcohol and water, respectively. As a result, 
evaporation from the set material causes dimen- 
sional contraction in both. 

Poly ether (Fig. 14-8). Polyether impression mate- 
rial, developed in Germany in the mid-1960s, has a 
polymerization mechanism unlike those of the 
other elastomers. No volatile by-product is formed, 
which results in excellent dimensional stability. In 
addition, its polymerization shrinkage ^^ is unusu- 
ally low compared with most room temperature- 
cured polymer systems. However, its thermal ex- 
pansion32 is greater than that of polysulfide. 

With the high dimensional stability of polyether, 
accurate casts can be produced when the material 
is poured more than a day after the impression 
has been made. This is especially useful when pour- 
ing the impression immediately is impossible or in- 
convenient. Another advantage of polyether is its 
short setting time in the mouth (about 5 minutes, 
which is less than half the time required for poly- 
sulfide). For these reasons, polyether is used by 
many practitioners. 

However, polyether has certain disadvantages. 
The stiffness of the set material is one such disad- 



Chapter 14 Tissue Management and Tm pr pssion Making 



I 




Fig. 14-8. Polyether impression material. 

(Courtesy Sullivan-Schein Dental.) 




Fig. 14-9. Addition silicone. 

(Courtesy Sullivan-Schein Dental.) 



vantage, which causes problems when separating a 
stone cast from the impression. Thin and single 
teeth, in particular, are liable to break unless the 
practitioner uses great care. Polyether is stable 
only if stored dry, because it will absorb moisture 
and undergo significant dimensional change. Poly- 
ether's relatively short working time may limit the 
number of prepared teeth that can be reliably cap- 
tured in a single impression. Isolated cases of aller- 
gic hypersensitivity33 to polyether elastomer have 
been reported (manifested as sudden onset of burn- 
ing, itching, and general oral discomfort). There- 
fore, the allergic patient's record should carry a 
warning against polyether's future use, and an al- 
ternative elastomer should be chosen. Recent im- 
provements in these materials have reportedly re- 
duced this problem. 

Addition Silicone (Fig. 14-9). Addition silicone 
was introduced as a dental impression material in 



the 1970s. Also known as poly(vmyl siloxane) (poly- 
siloxane is the generic chemical expression for sili- 
cone resins), it is similar in many respects to con- 
densation silicone, except that it has much greater 
dimensional stability 34 (equivalent to polyether 
polymer), and its working time is more affected by 
temperature. 22 The set material is less rigid than 
polyether but stiff er than poly sulfide. As with the 
other materials previously described, adverse 
soft- tissue responses have been reported ^^ One dis- 
advantage of this material is the setting inhibition 
caused by some brands of latex gloves. 36 The prob- 
lem is most apparent if a hand-mixed putty is used, 
but problems can occur if the tissues are touched 
with gloved hands immediately before impression 
placement. If the putty system is used, gloves that 
do not interfere with setting should be selected .3' 
Like condensation silicone, addition silicones are 
hydrophobic. Some formulations contain surfac- 
tants, which gives them hydrophilic properties, 38 



■ 



Section 2 Clinical Procedures -Part I 



imparting wettability similar to polyethers. 39 How- 
ever, these products also expand like poly ether 
when in contact with moisture ^° Addition silicone is 
generally used as a two-viscosity system, although 
monophase formulations are also available. It is eas- 
ier to trap bubbles when using the monophase." 

Manufacturer recommendations should be fol- 
lowed when a cast is being poured, and pouring 
should be delayed with some of the earlier prod- 
ucts. If this is not done, a generahzed porosity of the 
cast surface caused by gas from the impression ma- 
terial will develop. Newer products contain "scav- 
engers" that prevent the escape of gas at the poly- 
mer-cast interface. Addition silicone that contains 
scavenger material can be poured immediately. 



CUSTOM TRAY FABRICATION 

A custom tray improves the accuracy42 of an elas- 
tomeric impression by limiting the volume of the 
material, thus reducing two sources of error: 
stresses during removal and thermal contraction. 
Although reducing the bulk of an elastomeric im- 
pression material increases its accuracy, the oppo- 
site is true for reversible hydrocolloid impressions. 
In hydrocolloid impressions, dimensional change is 
due to water loss (or gain) from the surface of the 
impression. A bulky hydrocolloid impression has a 
lower surface area/volume ratio and is therefore 
less subject to dimensional change. 

Generally a custom tray is made from autopoly- 
merizing acrylic resin (Fig. 14-10), although thermo- 
plastic or photopolymerized resins are sometimes 




Fig. 14-10. Custom tray fabrication. A, Armamentarium. B, Outlining the border of the tray on the 
diagnostic cast. C, The tray should extend 3 to 5 mm from the gingival margin and about 3 mm beyond 
the most distal tooth. D, Softened baseplate wax is adapted to form a spacer. Typically two thicknesses 
will provide the recommended 2 to 3 mm of space. E, Spacer is trimmed to the pencil line. F, Wax is re- 
moved to form the tray stops. G, Covered with tinfoil. H, The foil is adapted to the stops. 

Continued 



Chapter 14 Tissue Management nnH Impression Making 



■ 



used. Thermoplastic materials can be softened in a 
waterbath and adapted either manually or with a 
vacuum former with a heating element (Figs. 14-11 
and 14-12). The accuracy of impressions made with 
a thermoplastic tray material or light-polymerized 
materials is comparable to tha