color atlas of laminate porcelain veneers

Book Editor: Gregory Hacke, D.C.

FIRST EDITION

Copyright © 1990 by Ishiyaku EuroAmerica, Inc.All rights reserved. No part of this publication may be reproducedor transmitted by any means, electronic, mechanical, or otherwise,including photocopying and recording, or by any informationstorage or retrieval system, without permission-in writing-frompublishers.

Ishiyaku EuroAmerica, Inc.716 Hanley Industrial Court, St. Louis, Missouri 63144

Library of Congress Catalogue Number 89-045808

George Freedman/Gerald McLaughlinColor Atlas of Porcelain Laminate Veneers

ISBN 0-912791-52-7

Ishiyaku EuroAmerica, Inc.St. Louis • Tokyo

Composition by TSI Graphics, St. Louis, MissouriPrinted and bound by Espaxs, S.A. Publicaciones Medicas,Rossello, 132, 08032 Barcelona, Spain.

DEDICATION

Dr. Fay B. Goldstep, my wife, whose encouragement andunderstanding, both personal and professional, were invaluable,and to Judy, to whom "the book" meant that Daddy was workingand unavailable for play. My parents, Bella and Wilhelm, foralways being there when I needed them. June Patterson, whohas been with me since my first day of practice. And Dr. LudwigFriedman, my godfather and first dentist; he taught me thatbeing a dentist is enjoyable, and that dental work does not haveto hurt.

George A. Freedman, D.D.S.

I consider it an enormous privilege to once again thank Judi,my wife, for the loving support she has given this project and thecheerful manner in which she accepted the many sacrifices itentailed. This book would simply not exist except for her helpand it is dedicated to her.

Gerald McLaughlin, D.D.S.

NOTICEDentistry is an ever-changing science. As newresearch and clinical experience broaden ourknowledge, changes in treatment are required. Theauthors and the publisher of this work have madeevery effort to ensure that the procedures herein areaccurate and in accord with the standards acceptedat the time of publication.

ACKNOWLEDGEMENTS

The vast amount of work involved in a project such as this textalways includes the help of a number of people, not all of whomcan be mentioned in this short space.

Certainly it is appropriate to recognize many of the people whoworked so diligently over the years to develop the new technol-ogy of porcelain bonding and to bring it to the attention of theworld. When writing a text such as this one, it is easy to give theimpression that the authors did all the work single-handedly.Nothing could be further from the truth. The concept andmethods of porcelain bonding had many parents, all of whomshould be justly proud for their various roles. Some people likeCharles Pincus, Michael Buonocore, Ron Goldstein, and RonJordan were amoung the pioneers of the esthetic field. We alsoneed to acknowledge some of the other many innovators in thefield, such as Thomas Greggs, Alain Rochette, John Calamia, andHarold Horn, all of whom made significant contributions to theconcept of porcelain bonding.

Then, too, there are the visionaries and teachers, such as JohnMorrison, Glynn Thomas, Robert Nixon, Robert Ibsen, AdrianJurim, and Roger Sigler who have done so much to increaseawareness of this exciting creation. All these people, and manymore, have contributed meaningfully to the nearly explosiveacceptance of porcelain bonding. Without the efforts and creativ-ity of these people and many others like them, there would be noneed for a book such as this.

There are others , too, who were of particular help to us in thegargantaun task of assembling the current state of knowledge ofthis exciting modality into a single text. For these people we owea special debt of gratitude. One of these individuals is Dr. GregHacke, our editor at IEA Publishers.

We especially would like to thank Omer Reed for his thoughts.His words are particularly appropriate to the situation of theCosmetic Dentist in his everyday practice. Our thanks also go toMichael B. Miller for his section on composite veneers inchapter 2.

For the many hours needed to assemble the section describingthe refractory laboratory procedure, we are indebted to AndreDagenais, R.D.T., and Carl L. Lee-Young. Similarly, we mustextend a special note of appreciation to Thomas Greggs, thedeveloper of the platinum foil technique, for his contribution tochapter 11. And once again we are indebted to Leon Silverstone,one of the pioneers in the field of enamel bonding, for the use ofhis priceless SEM photographs.

No less important is John Morrison's contribution, not only forbringing the technique to England, but also for his laminates andinlays that he provided for the text. His early work in thedevelopment of the techniques will prove a service for years tocome. We also wish to thank Roberta Baird, M.S. W., for sharingher thoughts about the concepts in chapter 1.

CONTRIBUTORS

Omer K. Reed, D.D.S.

Michael B. Miller, D.D.S., F.A.G.D.

Andre L. Dagenais, R.D.T.

Thomas Greggs, C.D.T.

In this time of change, a pivotal period when our society isshifting from the industrial to the information/service-driveneconomy, it is exciting to realize that a parallel revolution istaking place in the profession of dentistry. This paradigm shift isdriven by an extensive reduction in disease, an increase in dentalmanpower, and a discovery that over half our population,considered by the profession to be the "unmet need market," hasless disease in intensity and frequency than those who arepresently coming to see us. There is still another revolution thatis simultaneously taking place in materials, techniques, andphilosophy in dentistry.

The revolution in materials technology, as evidenced by theDuret micro-milling machine and other emerging systems, isleading to a dental office of the future that will no longer use thetraditional plaster techniques. A patient can, without an impres-sion or temporary, have the finest and most accurate veneer,inlay, crown or bridge placed during the first visit, creating amore profitable win-win situation for both the doctor and thepatient.

The "New Dentist" of the 90's and the turn of the century willeither be serving the commercial forces that presently exist in thehealth care system, or he will be "private care," providingunique, interdependent, and service-oriented procedures topeople. The new technology for veneering or laminating of labialand buccal surfaces for cosmetic and functional reasons allows theprofession to offer a new level of service and to open up anentirely new population of potential patients in the realm ofcosmetic dentistry. This new technological development in thefield of cosmetic dentistry comes along just in time to meet thefelt needs and wants of a market that is in the midst of a parallelrevolution in which "free time" is any time and the affluentconsumer perceives an attractive smile no longer as a luxury, butrather a necessary part of the prevailing lifestyle.

A full crown may unnecessarily destroy the incisal guidance,the contact, morphology, food-flow pattern, and phonetics thatalready exist in the patient's mouth. The new laminate technol-ogy now gives the dentist a viable alternative to offer to hispatients. The best dentistry is no dentistry, and people gladlyremunerate us for being well and for staying well, and beingassured that they are functionally sound. In this light then, it ispossible to conceive that the less we do, the more we arerewarded for our services; especially if we understand theconcept of "values driven co-development" of the fee in ourmarketing efforts.

The emerging laminate technology dovetails perfectly with theneeds and wants of this new affluent consumer of dental services.Laminates is a topic that should be high on the list of new skillsthat every dentist should be learning if he is to be a successfuland prosperous part of the new dental market of the 90's andbeyond. In the following chapters, Drs. Freedman andMcLaughlin appropriately and effectively present those neces-sary skills for the 90's and beyond.

Omer K. Reed, D.D.S.

INTRODUCTION

In ancient times, people sought dental care almost exclusively foresthetic reasons. In some cultures, teeth were hollowed out withprimitive drills for the purpose of implanting precious stones. Inother times, teeth were filed down to points or sharpened toimitate the dentition of animals. Sometimes they were (and stillare in some cultures) knocked out entirely.

Through several thousand years, dentistry changed but little.In this century, however, science and technology have providedthe necessary basics that have propelled dentistry into fieldsunimaginable only a short time ago.

We have become proficient at saving, filling, and straighteningteeth, and especially at educating the public about the impor-tance of good dental care. As a result, more and more peoplehave come to regard teeth as an essential necessity of life. Nowthat we can maintain teeth in relatively good health for an entirelifetime, much of the attention has again turned to their appear-ance.

Thus we have come full turn. Man, initially concerned withnothing more than dental esthetics, has gone the full cyclethrough health and function, and is now back to his initialconcern.

Dentistry is fortunate that at this particular time of interest incosmetic dentistry there are many materials and proceduresavailable to patients-and more are being developed all thetime.

The objectives of Cosmetic Dentistry must be to provide themaximum improvements in esthetics with the minimum traumato the dentition. There are a number of procedures that begin toapproximate the ideal parameters of Cosmetic Dentistry, mostnotably that of porcelain veneers.

Porcelain veneers are a recent and very exciting developmentin the dental armamentarium. They enable the dentist to changethe appearance, size, color, spacing, and, to a minor extent, thepositioning of the teeth. Many veneering procedures can beaccomplished with little or no preparation of the natural denti-tion, and commonly, anesthesia is not required.

This text is intended to provide the practicing dentist and thelaboratory technician with a concise view of the state of the art inthe design, manufacture, and clinical application of porcelainveneers. It is important for the reader to understand that thistechnique is in its infancy; many changes in the years to come willevolve and improve it, including innovations that will radicallyalter some of the concepts in this text. There is, however, a needwithin the profession for information about porcelain veneers atthis time.

This book represents the clinical experiences of the authors,and it is our sincere desire that both dentists and technicians willuse it as a basis on which they can expand their knowledge inorder to provide better and more conservative treatment.

COLOR ATLAS OF PORCELAIN LAMINATE VENEERS

The significance of the teeth to smiling and

to the face in general should not be underes-timated. Teeth contribute an important part

to what we term "appearance". A person'sappearance and, more importantly, his per-

ception of his appearance have a vast influ-

ence on his self image, which is proportion-

ally related his confidence (Figs. 1-1, 1-2,1-3).

Fig. 1-2

Mg. 1-3

CHAPTER I THE DEMAND FOR COSMETIC DENTISTRY

Confidence, in turn, enhances personal relationships. Peoplelook up to and like to have dealings with others who have faith inthemselves. This self-assurance is readily recognizable in theconversational manner of a person. Those who master the art ofpersonal relationships are more likely to succeed in today's highlyinteractive society.

Unattractive teeth are particularly detrimental to an individu-al's chances of success because they tend to negatively alterperceptions about cleanliness, health, sincerity, and truthful-ness.

Which segments of the population are more likely to beconcerned with esthetics and self-image?

Single men and women are possibly the most conscious of theirappearance. It is this group that consumes the largest share ofclothing and cosmetic products. In trying to make themselvesattractive to the opposite sex, they have become sensitized toesthetics. Nearly every advertisement in print and on televisionutilizes models with perfect dentition. Rather than a remotepossibility for some, this state is now a basic necessity. In theauthors' experience, it is singles who most commonly seekcosmetic treatment.

Careers are understandably important to both men and womentoday. Many jobs involve extensive personal contact with bothemployers and employees. In the process of positioning one's selffor advancement, grooming and appearance are so highly valuedthat career people regularly attend lectures that discuss every-thing from hair styling to shoe shining. Certainly, in light of theabove discussion of interpersonal communication, teeth form avery great part of a person's presentability.

As industries are shifting more to service and service-relatedareas, corporations are recognizing that each employee repre-sents the company to customers and the public. Since corporateself-image is just as important as personal self-image, a companywill naturally tend to hire, retain, and promote persons who meettheir esthetic requirements, which include neatness, cleanliness,and general appearance. A corporation does not wish to berepresented by an employee whose unesthetic smile might harmhis self image, which may possibly impair his communicational ornegotiating abilities.

The middle-aged and the elderly are often a forgotten group incosmetic dentistry, but this trend may change. People expect tokeep their teeth longer and now expect to keep them betterlooking as well. The staining and the craze lines that often appearin the forties and fifties are no longer solved by extractions anddentures. This group consists of persons at the height of theircareers and in excellent physical shape, and they do not want anyreminders that time is progressing relentlessly. Menopause andmid-life crisis are other underlying conditions that may inducethis age group to seek extensive cosmetic restructuring of theirteeth.

It is occasionally noted with patients who have undergonerejuvenating plastic surgery that their teeth are the oldestappearing facial features. Plastic surgeons must make theirpatients aware that along with soft tissue procedures, dentalcosmetic treatment may be indicated.

Adolescence is a very trying time both emotionally andphysically. It is also a period during which peer pressure and theneed to be accepted are the strongest. The slightest physicaldeviation can undermine the confidence of a youngster andpossibly affect his continued normal development. Adolescentsare constantly preening in front of mirrors, and thus have all themore time to become self-conscious about dental defects. Whatbetter way to eliminate these deleterious effects than through anon-invasive, reversible cosmetic procedure.

The above are just a few highlighted examples. Everyone is, toa greater or lesser extent, concerned with self-image and cantherefore benefit from an improved dental appearance.

THE RELATIONSHIP BETWEEN APPEARANCEAND SUCCESS

When someone unknown to us is described as a successfulperson, we immediately form a mental picture. In our minds wehave actually created our own ideal of success. While theimagined person will vary greatly from one mind to the next,certain qualities will be present in all cases: the successful personwill be confident, well dressed, well groomed, and will invariablybe smiling.

Our imagination often guides our expectation, and consciouslyor subconsciously we attempt to emulate an appearance ofsuccess in our own actions. We, too, wish to be smiling,confident, respected, and sure of ourselves.

Will an individual with dental esthetic problems appear to besuccessful?

If on smiling and conversing the dental problems are visible,then this will create a picture of uncleanliness and/or poorattention to grooming. Such an individual would not be per-ceived as the responsible type of person to whom one couldentrust an important task. After all, it may be felt that if he isinattentive to personal detail, he is just as likely to be careless atwork.

This entire case against the person with unesthetic teeth hasbeen made without regard to his personality, integrity, qualifi-cations, and experience. Yet the judgment has been made at thefirst contact, often the meeting that sets the tone for an entirerelationship.

CHAPTER I THE DEMAND FOR COSMETIC DENTISTRY 5

The prejudice that has been created doesnot distinguish between decayed teeth, lostor broken teeth, or teeth stained extrinsicallyor intrinsically (Figs. 1-4, 1-5).

Fig. 1-5

The cause of the esthetic liability is rarely determined.Whether the factors are neglect, medication, or genetic, seems tohave no bearing on the negative impact that poor dental appear-ance creates in the mind of the observer.

Persons with the esthetic problems described above will oftenresort to compensatory behavior. This line of action only servesto aggravate the situation.

Some people never smile at all, or at best exhibit a very tightgrin. This is not commonly taken as an indication of an outgoingpersonality, and the person is assumed to be smug, conceited,self-centered, antagonistic, and incapable of being friendly. It isunlikely that this individual will be easily accepted either sociallyor professionally.

Fig. 1-4

6 COLOR ATLAS OF PORCELAIN LAMINATE VENEERS

Fig. 1-6

Others may attempt to compensate bycovering their mouths with their hands. Be-sides making their conversation difficult tounderstand, this gesture implies self-doubt.While this maneuver may effectively hidethe dental problems most of the time, it isunlikely to lead to a successful outcome.Combined unintelligibility and the appear-ance of insecurity tend to show an individualin a rather poor light.

Yet another compensatory mechanism is the avoided look. Thedentally-compromised person looks down or away from a conver-sational partner. This is interpreted by the observer as shiftiness,uncertainty, or vacillation, and usually the dental imperfection isnot at all hidden.

As an individual begins any of these behavior patterns, hispartner will lean in or come closer to re-establish greater eyecontact. The partner cannot understand why the dentally unes-thetic person is setting up these barriers and he tries to undothem. As there is greater eye-to-eye or eye-to-lip contact, thedefensive person becomes ever more insecure and attemptsfurther avoidance.

At any given time, our body language is sending messages tothose around us. If these messages are strong and confident ones,we will appear to be successful. As the feedback from othersconfirms and reinforces these feelings, these perceptions becomeself-fulfilling. If we do not appear successful due to an unestheticdentition, and if we radiate messages of antagonism, insecurity,and defensiveness, it is likely that similar feelings will bereflected from those with whom we associate.

It is wrong to assume that a good appearance will guaranteesuccess, but it is a safe bet that a poor appearance will hindersuccess greatly.

REFERENCES

1. Nierenberg, G.I., Calero, H.H.: How to Read a Person Likea Book, New York, 1971, Simon and Schuster.

Dr. Charles Pincus was a Beverly Hills practitioner, and partof his patient load came from the people in the movie industry.Among these were makeup personnel from various studios.When they brought their stars' dental problems to Pincus, hebegan experimenting with certain techniques to improve theirappearance.

The only important considerations for Pincus at that time wereesthetics, and to a lesser extent, comfort. The dental work had tolook good for close-up camera work, to be comfortable in themouth for extended periods, and to be placed so that it would notinterfere with speech.

Ultimately, Pincus developed a porcelain facing that fulfilledthese conditions'. He baked a thin layer of porcelain ontoplatinum foil and designed the appliance so it would not interferewith normal oral function. As you would expect, it was not wornin the mouth continuously. The stars could not eat with theirfacings and wore them for performing only. They were notbonded onto the teeth (suitable technology not yet having beeninvented); in fact, they were glued temporarily into place withdenture powder.

Thus was born the "Hollywood Smile". Through the years, thishas become the generally accepted lay standard of dental cos-metic excellence. As the world's exposure to films increased,dentists were besieged with patients desiring the movie stars'smile. These people did not realize that much of the dentalperfection that they saw was as much of an illusion as the rest ofthe film. They also could not possibly know the limited functionof these esthetic prostheses.

Dentists have spent the intervening years trying to catch up totheir patients' expectations. Various materials were used in thetechnique of Pincus, and they all shared the same major limita-tion. Without any means of secure attachment to teeth, theywere of little practical use. This changed dramatically in 1955with the discovery of bonding. Finally, dental materials could besecurely attached to tooth structure, but the materials availablethen did not fulfill the needs of esthetic dentistry. The firstattempts at esthetic bonding made use of dental acrylic, and wereunsuccessful due to the unpleasant taste of the residual mono-mer, and the stains and mouth odors that the acrylic materialretained. It was hardly an esthetic solution.

Then, in 1972, Dr. Alain Rochette published a paper detailingan innovative combination of acid-etched bonding of enamel witha porcelain restoration. The porcelain itself was not etched, butwas pre-treated with a coupling agent to promote chemicaladhesion of an unfilled resin luting agent. First in French, andlater in English,4 he described the successful placement of acustom-fabricated porcelain prosthesis to repair a fractured in-cisal angle.

CHAPTER 2 THE HISTORICAL DEVELOPMENT OF PORCELAIN LAMINATE VENEERS

Unfortunately, although Dr. Rochette reported excellent re-sults over a three year observation period, it seems that hiscreation was too far ahead of its time, and nothing more washeard of the technique for many years. Instead, the emphasis wasplaced on improving the plastic dental materials used for directapplication to the etched enamel. Acrylics and unfilled resinswere followed by filled resins and then macrofill compositeresins. Each material represented an improvement over theprevious generation of materials, but each in turn was abandonedbecause none fulfilled the major requirement of esthetic resto-ration: creation and maintenance of an improved appearance.

For all these attempts, the dream of restoring a dentallycompromised patient's esthetic appearance without resorting tofull coverage was just that-a dream. Dentistry had not yetdeveloped a cosmetic and functional device that could be placedon the dentition permanently.

PREFORMED PLASTICLAMINATES

In the 1970's, a dental cosmetic techniqueusing preformed factory processed plasticlaminates was presented to the dentalprofession5,6 ( Mastique, Caulk-Dentsply,Milford, Delaware). This technique held thepromise of a simple, durable treatmentwhereby unesthetic teeth could be cosmeti-cally treated without resorting to full crowncoverage.

Fig. 2-1

The technique consisted of matching pre-formed plastic laminates to the teeth to beveneered and then of modifying them chair-side until a fairly close adaptation wasachieved.

Fig. 2-2

10 COLOR ATLAS OF POCELAI \ LAMINATE VENEERS

Fig. 2-3

Then, through the use of a compositebonding agent, the laminate was bonded tothe etched tooth surface. By the judicioususe of various shades of composite, the un-derlying deformities could be masked, andan esthetic result was obtained (Figs. 2-3,2-4).

Fig. 2-4

Fig. 2-5

The Mastique laminate was relatively easyto place on teeth but the kit provided only amoderate selection of different shapes andsizes. Once an appropriate veneer was cho-sen, the dentist was required to shape it to fiton the selected tooth. Thus while the bond-ing was simple, the procedure still remainedtechnique sensitive, and, correspondingly,various levels of success were reported .

Subsequently, as dentists realized the dif-

ficulties in adapting plastic laminates, labora-

tories began fabricating them using a heatmolding technique. This again enhanced the

use of these veneers for a time. But the

increased use of plastic laminates brought to

the fore certain inherent problems with this

treatment modality. The most serious draw-

back was an inadequate bond formed be-

tween the composite bonding agent and the

plastic laminate7 . This gave rise to delamina-

tion, chipping, and marginal percolation.

Fig. 2-6

The entire laminate would often just pop

off the tooth, as it did for this patient's lateral

incisor. Some of these failures were due to a

weak bond, and some to the memory that theplastic exhibited. When the laminate was inany way stressed into place during the bond-

ing procedure, it tended to spring back to its

original shape at some time after.

Fig. 2-7

Any pressure at the marginal areas

chipped off sizable segments of the plastic

veneer, leaving portions of the underlying

composite exposed. The subsequent differ-

ential staining was one of the major causes of

cosmetic failure.

Fig. 2-8

Fig. 2-9

The laminated plastic veneers had to beprotected from occlusal forces. Where anybiting or clenching stresses were applied, ifthe veneer did not debond, it would wearvery quickly.

The earlier plastic veneers were bondedwith self-curing resins. These materials con-tained amines, which caused discolorationand darkening over time. Such was the situ-ation with the two-year-old plastic veneersover the maxillary lateral incisors shownhere.

Fig. 2-10

The weak marginal area also permitted thepercolation of oral fluids under the veneer, inbetween it and the composite. After a num-ber of years, it was quite common to seepooled areas of stain showing through theplastic.

CHAPTER 2 THE HISTORICAL DEVELOPMENT OF PORCELAIN LAMINATE VENEERS 13

Fig. 2-11

The longevity of these laminates can nowbe evaluated. While some have lasted fiveyears or more, very often the esthetic bene-fits were gone in two. The plastic veneersdone for this patient are typical. The first twophotographs were taken about two hoursapart, demonstrating that the improvementis both dramatic and immediate. The thirdphotograph, however, which was taken abouttwo years later, shows the disappointing lon-gevity of the preformed plastic laminate sys-tem (Figs. 2-11, 2-12, 2-13).

Fig. 2-13

Plastic laminate veneers were a suitable technique in their owntime and, perhaps,had their introduction not coincided with theadvent of light-cured microfill composite freehand veneers, theymight have gained a greater acceptance and use by the profes-sion. Their greatest contribution to dentistry was that they madethe profession aware of the esthetic possibilities of veneering.

DIRECT RESIN VENEERS

Michael B Miller, D.D.S.

Direct resin veneers have be.en the glamour procedure inCosmetic Dentistry and are most responsible for its explosivegrowth. They permit "instant", one-appointment enhancementof our patients' smiles and allow us to control the entirefabrication process, rather than depending on the laboratory.This control, however, places more artistic responsibilities on ourshoulders. The dentist must be willing to learn layering, sculpt-ing, and finishing techniques, or these veneers will be frustratingto him and a disaster for his patient.

Direct veneers may be done without any tooth preparation,although the results generally will not be as esthetic as a veneerdone after enamel reduction. Even though these veneers areslowly being replaced by porcelain veneers as the optimalesthetic option, freehand veneers still have their place in theCosmetic repertoire.

While many materials are used for direct veneering, microfillsare the most responsible for the acceptance of this modality.Because of their translucent and polishable nature, microfills canbe made to mimic enamel almost as well as porcelain. However,microfill restorations are susceptible to chipping, and the patientmust accept the fact that these veneers do require periodicmaintenance. To minimize this tendency, direct resin veneersoften utilize several layers of various materials, each with its ownindividual strength.

Since direct veneers are done without laboratory support,there is neither a lab fee nor the chance that the technician willnot follow the dentist's instructions. Considering the lesser costof this procedure, direct veneers give rise to a lower fee thanporcelain. The costs of porcelain veneers unfortunately can beprohibitive to some people, especially younger patients. In thisinstance, direct veneers may serve as an entry-level procedure,and may be remade in porcelain at some point in the future whennecessary and affordable.

CHAPTER 2 THE HISTORICAL DEVELOPMENT OF PORCELAIN LAMINATE VENEERS 15

This female patient had been "bonded" byanother dentist. In fact, there was merely alayer of opaque on her teeth. She could notafford optimal dentistry.

Fig. 2-14

The opaque was removed. Direct veneerswere sculpted onto the teeth, this time in-cluding the cuspids, using only one shade ofan opaque microfill. This allowed the darkteeth to be covered to the patient's satisfac-tion without requiring much time spent withopaquers and tints, which procedures wouldhave resulted in a substantial increase of thefee involved.

Fig. 2-15

Fig. 2-16

The male in this picture had a number ofproblems: a Class III occlusion, rotatedteeth, and (in his own perception) teeth thatwere too dark. Orthognathic surgery andorthodontics were prescribed prior to cos-metic restorative treatment. The patient de-clined this treatment plan. He wanted only"straight white teeth".

Fig. 2-17

Initially, the patient was subjected to vitalbleaching, but the color improvement wasinadequate.

Fig. 2-18

The maxillary and mandibular anteriorswere then veneered to give the patient theappearance he desired. Bonded veneerswere chosen instead of porcelain because thepatient wanted such a radical change. In theevent that the patient is not satisfied afterthe procedure, or if he ever decides to havehis malocclusion corrected, it will be rela-tively easy to remove the bonded veneersand to replace them with porcelain.

REFERENCES

l. Bounocore, M.A.: A simple method of increasing the adhe-sion of acrylic fillings to enamel surfaces. J Dent Res,34:849-853, 1955.

2. Pincus, C.L.: Building mouth personality. J Calif Dent Ass,14(4):125-129, 1938.

3. Rochette, A.L.: Prevention des complications des fracturesd'angle d'incisive chez I'enfant: reconstitution en resine ou enceramique dont la retention n'est due qu'a (adhesion. Entre-tiens de Bichat, Odonto-stomat. Paris 1972. Expansion Scien-tifique Francais, p. 109-114.

4. Rochette, A.L.: A ceramic restoration bonded by etchedenamel and resin for fractured incisors. J Prosth Dent,33(3):287-293 March, 1975.

5. Faunce, F.R.: Tooth restoration with preformed laminatedveneers. Dent Survey, 53(1):30, 1977.

6. Faunce, F.R.: Laminate veneer restoration of permanentincisors, JADA, 93(4):790, 1976.

7. Boyer, D.B., and Chalkley, Y.: Bonding between acryliclaminates and composite resins veneers. J Dent Res, 61:489-492, 1982.

Fig. 3-1

There is yet another group of materialsthat is becoming increasingly important indentistry. Known as "coupling agents", thesematerials nearly function as true dental ce-ments. These materials generally have tre-mendous adhesive strength but such lowcohesive strength as to be totally useless ascements by themselves. In combination withother materials, however, they can serve thesame purpose as true cements.

A typical example of a coupling agent usedin dentistry can be found in attaching BIS-gma resins to porcelain. Porcelain representsa particularly difficult surface for cementationif the cement bonds are to be submerged inwater. Bond strengths of 1200 psi in thetensile direction are not unusual when at-taching resins to porcelain in a dry environ-ment, but after only 48 hours of submersionthe two surfaces nearly fall apart'. Certainintermediary treatments of the surfaces canmake an extraordinary difference. For in-stance, when the porcelain has been coatedwith a monomolecular layer of an organo-functional silane before being covered bythe resin, the bond strength becomes formi-dable.

CHAPTER 3 FUSION: THE BONDING THAT MADE IT ALL POSSIBLE 21

An organo-functional silane is composed oflong-chain silicon molecules having a reac-tive organic group at one end and a reactiveinorganic group on the other.

Fig. 3-3

when me porcelam ls coaieu with mane,the inorganic end of the silane moleculefirmly attaches to the inorganic porcelain.The net result is that the normally inert andunreactive inorganic porcelain surface be-comes coated by a sheath of highly reactiveorganic groups. This new surface can thentightly adhere to the organic components ofthe dental resin, allowing the resin to act as atrue cement with the silane coated porcelain,but without the restrictions of needing a thinfilm thickness.

Fig. 3-4

Even more important for porcelain lami-nates, the chemical bonds which form be-tween the porcelain and composite are notonly stronger, but also water resistant. Whilemost adhesive bonds tend to diminish instrength after exposure to the oral environ-ment, substantial evidence shows that thesilane/porcelain bond actually becomesstronger after submersion and thermalcycling2 ° 3 .

MICROMECHANICAL ATTACHMENT

The basic technique of micromechanical attachment haschanged little since it was first described in 1955 3 . Working inNew York, Michael Buonocore noticed that the application of aweak acid to the surface of enamel results in an irregular andpitted surface. Buonocore then flowed dental material onto thisroughened surface to create a mechanical attachment betweenthe material and the tooth. From this simple beginning hassprung "The Bonding Revolution".

COMBINED ATTACHMENT

The processes of micromechanical reten-tion and chemical retention are not mutuallyexclusive. In fact, they are potentially aug-mentive. Since chemical retention is directlydependent upon the total surface area, thehigher the surface area, the greater the po-tential bond strength. Etching the enamelincreases the enamel surface area nearly ahundredfold'. Thus, etching before cement-ing can greatly enhance the bond strength .

By 1983, the combination of etching and pre-treatment with acoupling agent had been incorporated into the porcelain laminateveneer techniques6.7.8 Simple bonding was used on the enamelsurface, but the inner surface of the porcelain veneer was etchedwith hydrofluoric acid, and then treated with a silane beforebeing bonded into place. This simple change in techniqueresulted in a great increase in the bond strength of composite toporcelain. This seemingly important improvement in the bond-ing technique, however, resulted in no increase in the total bondstrength because, like any chain, the connection between theveneer and the tooth breaks at its weakest point.

This figure illustrates the relative strengthof the various components of the connectionbetween the tooth and the laminate whensimple bonding is used. Even without si-lanization of the porcelain, the bond strengthof composite to etched porcelain exceeds thestrength of the bond between etched enameland composite.

In 1983 coupling agents were discoveredwhich were effective on etched enamel. Thefirst of these consisted of phosphate esters ofBIS-gma. The presumed point of attachmentof the enamel coupling agent and the enamelis a phosphate/calcium bond. Although theexact mechanism has not been fully eluci-dated, one study showed an increase in bondstrength of 86 percent when etched enamelwas pre-treated with a coupling agent beforebeing coated with composite resin9 . Laterstudies with improved coupling agents haveshown an immediate improvement of 50 per-cent, with a 24 hour improvement of 170percent. Now, composite to enamel bondsof 3,000 psi are not uncommon

Finally, all the components necessary for anew and improved retention system hadbeen discovered. All that remained was toput them together in a coherent system. In1983, in a paper on porcelain veneers, a newterm entered the dental vocabulary: enamelfusion. McLaughlin introduced this term todescribe the combination of both microme-chanical and chemical attachment on all in-terfaces of a restoration to a toothl° . Bydefinition, each surface being fused firstwould be etched and then cemented. Theuse of enamel fusion requires either usingmaterials which are capable of both cemen-tation and bonding, or alternatively, using"coupling agents" as intermediaries.

By using the fusion process, the total bond strength ofporcelain to tooth is increased by 66 percent over simplebonding. When using this process, the dentist is able to adhereporcelain veneers on to the tooth surface with greater tenacitythan has ever before been possible. In fact, one report indicatedthat the strength of the attachment between a porcelain laminateand enamel after the fusing process exceeds the strength of thebond between the enamel and the underlying dentin.

In summary, then, present day fusing is made possible by twothings: the mechanical gripping afforded by etching, and thechemical attachment afforded by coupling agents. To betterunderstand exactly what is happening in the fusing process, it ishelpful to examine each of the components separately. First wewill look at what happens to the tooth.

When a mild acid is placed on the surface of a tooth, aroughened, pitted surface results due to one of the morphologicalcharacteristics of human enamel. Microscopically the enamel iscomposed of bundles of prisms or rods which radiate in adirection from the center of the tooth toward the periphery.Surrounding each of these prisms and serving as "mortar" forthem is the substance known as interprismatic enamel. It isbecause of the difference in resistance to acidic attack betweenthe enamel prisms and the interprismatic enamel that the acidwash creates a retentive surface. In some areas of the enamel, thecenters of the prisms erode more rapidly than the interprismaticenamel. In other areas, the reverse will happen, and theinterprismatic enamel erodes more thoroughly than the prismsthemselves. As a result, four major etching patterns of theenamel are reported in the literature.

Fig. 3-10

The Type I etching pattern is createdwhen the prism shows less resistance to theacid than the interprismatic enamel. Thispattern appears as a series of relatively sym-metrical "holes" or "pores" in the enamel,extending to a depth of approximately 20microns.

The average width of the craters found in the Type I etchingpattern is about five microns. It is partly for this reason that manyluting agents utilize a filler particle size of no greater than fivemicrons. A generally held belief is that by restricting the particlesize to five microns or less it is possible for the filler particles toenter into the lumen of the etched enamel. This characteristic ofluting composite is of dubious value, however, since even ifpenetration of a five micron filler particle may be possible andreasonable with a Type I etching pattern, it is probably of nosignificance whatever in Types II, III or IV.

The Type II etching pattern is createdwhen the interprismatic substance erodesmore rapidly than the enamel prisms them-selves. The resulting surface has been de-scribed as looking like a view of treetopswhen seen from above. The invaginationseroded into the enamel are obviously muchnarrower than that of the Type I etchingpattern, but this surface is still suitable forfusing.

Fig. 3-11

It is interesting to note that even thoughTypes I and II etching patterns are exactreverses of each other, they will often occurin adjacent areas of the same tooth, some-times even in adjacent prisms.

Fig. 3-12

While Type I and II etching patterns are suitable for mechan-ical retention, Type III is not. In a typical Type III etchingpattern, no rod structures are evident. This etching patternresults when the enamel consists of a homogeneous mass ratherthan the familiar rod and interprismatic enamel structure.

It was recognized early that deciduous teeth frequently exhibita stratum of homogeneous enamel in their outermost layer. It isbecause of this homogeneity that an application of acid results ina simple reduction of enamel bulk rather than the differentialetch required for mechanical retention. As such, the Type IIIetching pattern can be troublesome for fusing. To make mattersworse, prismless enamel is not confined to deciduous teeth ashad once been believed. An increasing number of reports indi-cate that the cervical two-thirds of premolar and molar crowns isoften completely devoid of rod patterns after etchings11,12,13.

Fortunately, the prismless enamel layer is usually confined tothe outer 13 to 20 microns of the enamel. It is therefore possibleto erode past this prismless layer using the etchant. An application of 30 percent orthophos-

phoric acid for 60 seconds on enamel usuallyresults in a loss of about 10 microns in surfacecontour and about 20 micron depth of histo-logic change. Since the prismless enamelusually extends no deeper than 20 microns, itis obviously possible to easily erode past thislayer with the application of 30 percent or-thophosphoric acid. Beneath the prismlesslayer, the underlying structure usually exhib-its one of the other three etching patterns.Thus the presence of prismless enamel dic-tates that the etching time for proper fusingbe considerably longer than that required bynormal enamel.

Fig. 3-13

The fourth etching pattern (Type IV), is acombination of Type I and II. It exhibits whatat first appears to be a random irregularity inthe surface of the enamel. Some dentistsbelieve that the irregularity and apparentrandomness of the perforations enlarged intothe enamel create the ultimate surface forcomposite fusing. (Figures 3-10 through 3-14courtesy Dr. Leon Silverstone)

CHAPTER 3 FUSION: THE BONDING THAT MADE IT ALL POSSIBLE

Over the first 48 hours, many forces combine to hold thecomposite in contact with the enamel. These include not onlymechanical gripping, but also chemical, and Van der Wallsforces. After 48 hours in the mouth, however, the chemical,electronic, and Van der Walls forces diminish to such an extentthat they are insignificant. These three forces are effective onlywhen the enamel and composite resin are in extremely intimatecontact. Since water has a much greater affinity for both theenamel and composite resin than they have for each other, waterfrom the patients saliva gradually insinuates itself between thesetwo layers, "prying" them apart. After 48 hours, the mechanicalretention is all that remains for standard bonding.

Still, this bonding is quite strong. The currently acceptedvalue for the bond strength of composite to etched enamel inboth tensile and shear directions is between 980 and 1400p s i 14 ' 1 's. This is extremely high for simple mechanical gripping forthese materials. The obvious explanation for this surprisinglyhigh bond strength is that the mechanical bonding is not "simple"at all. During the etching process, the enamel "pores" becomeenlarged. These pores not only penetrate vertically into thetooth's surface, but also interconnect (Bergman and Hardwickhypothesize that they are pathways used for transport of ions andtissue fluids) 16,17. The increase in size of these interconnectingpores allows the relatively large resin molecules to penetratethrough the subsurface of enamel and to interconnect with otherresin tags. This results in a very high degree of resin interlockingaround the enamel crystalite itself.

In order to consistently create these exceptional bondstrengths, meticulous attention to detail is required prior tofusing. While enamel is an excellent substrate for fusing, in itsnatural state there are several mechanical impediments to form-ing a strong mechanical attachment.

Proteins from saliva continually adsorb to the surface of teeth,even in high abrasion areas. As a result, the enamel is normallycovered by a thin organic layer called pellicle18. This pelliclethen serves as a point of attachment for plaque. The plaqueproducts, along with solid food constituents and fluids form acontinuous plaque/pellicle complex. This layer serves as aneffective barrier to etching by mild acids. In 1973 Mura and hisco-workers showed that the etchant alone was not sufficient to dothe job". This was further demonstrated by Gwinnett20 in 1976when he showed that enamel which was etched without amechanical pre-cleaning was often contaminated by remnants ofthe pellicle as well as by microorganisms.

The obvious conclusion is that in order to maximize theeffectiveness of the etchant, the enamel must be pre-treated witha thorough prophylaxis. The usual cleaning agent is unfluori-dated, unflavored pummice, despite the fact that there is supportin the literature that standard prophylaxis paste, even withfluoride, is equal in effectiveness. Much has been written about

28 COLOR ATLAS OF PORCELAIN i.1\11\ TE : I NEER

the potential advantages of using either a rubber cup or a bristlebrush to clean the enamel 22,23,24,25 but there appears to be noqualitative differences between a thorough prophylaxis per-formed with either instrument. Thus the choice seems to besimply a matter of operator preference. There also has been someinterest in the possibility of using a diamond bur to lightly "dustover" the enamel, both cleaning the enamel and removing theoutermost layer of its surface, and some of the literature supportsthis method 26.27.

If a diamond instrument is used, however, caution must beexercised. Remember that the porcelain laminate has beenconstructed to carefully fit the tooth; the dimensions should notbe randomly altered after the impression has been taken, orplacement could be complicated. Prudence also is particularlyindicated in the case of some of the less conservative toothpreparations (Type IV,V). If the dentist has already eliminated allthe enamel that can be safely removed, then good judgmentwould dictate that the use of a diamond bur be avoided duringthe attachment phase.

The method used for cleaning the enamel is not critical. Whatis absolutely vital, however, is that complete cleaning beachieved on all surfaces to be bonded. This also includes theinterproximal areas, as well as any areas on the lingual of thetooth that are going to be covered by porcelain. Also, it is goodpractice to clean and etch slightly beyond the actual area to becovered by porcelain whenever possible. This will allow forminor discrepancies in placement and for a smoother transitionfrom tooth to porcelain.

The result is that there is nearly always a need to clean theenamel interproximally. This can be achieved using polishingstrips or a Prophy Jet (Dentsply, York, Pennsylvania). TheProphy jet uses a stream of sodium bicarbonate and water underpressure much like a miniature sandblaster.

Fig. 3-15

ETCHING

Many etching materials are now on themarket. They are all composed of ortho-phosphoric acid of between 35 and 50 per-cent concentration. Some of them also havebeen combined with filler to make a gel.While they are all clinically effective, the gelsand liquids require two slightly differenttechniques. In using the liquid, one mustcontinually stir the liquid on the surface ofthe enamel. Be especially careful to avoidpressing against the enamel during this phasebecause even slight pressure can burnish theenamel rods and diminish ultimate bondstrength. If a gel is used, the stirring is notnecessary.

Until recently, the accepted time for a proper etch has been 60to 90 seconds28°29. Some interesting research, however, hasmade those times equivocal30,31,32. Further research in this areais needed to clearly determine the optimal etching period.

After the appropriate amount of time (usually around 60seconds), the etchant is rinsed off. Since the gel is so muchthicker, it naturally requires more time to remove. Rinse theliquid for at least 20 seconds, and the gel for at least one minutebefore proceeding. Though using a gel takes longer than a liquid,it stays where it is placed. This becomes important when thereare any areas of exposed dentin or cementum. In such cases thegel can be carefully placed to avoid the dentin and cementum.The use of a syringe is often helpful for this process.

Once etched and rinsed, the enamelshould be completely dried with clean oil-free air. The enamel should have a "frosted"appearance, as shown here.

Fig. 3-16

If it is still glossy, then repeat the etching step. If the acid hasbeen allowed to stay on the enamel too long, the tooth will showan opaque, white, chalky appearance (as opposed to "frosted")due to the production of an insoluble precipitate. The precipitatestays behind after rinsing, clogging the roughness created by theetching. The result is a diminished bond strength. The solution:repolish the surface and re-etch.

After etching and drying, it is important to avoid contamina-tion of the surface. Among the list of possible contaminants is oilfrom the fingers, talc from gloves and saliva. Even a few secondsof exposure to saliva is sufficient to diminish the bond strengthdramatically. If the etched enamel becomes contaminated, it canbe re-activated by a ten second exposure to the etchant. Thisshort treatment with the etchant both cleans the etched surfaceand raise up its energy level so it will be chemically ready to reactwith the composite.

3 0 COLOR ATLAS OF PORCELAIN LAMINATE VENEERS

Fig. 3-17

By comparison to enamel, the porcelain/composite interface seems much simpler.Unetched, unglazed porcelain presents a mi-croscopic surface that is somewhat porous.This figure shows unetched/unglazed dentalporcelain at a magnification of 200X.

Fig. 3-18

Magnified to 2,400X, it has this appear-ance.

Fig. 3-19

The application of hydrofluoric acid to thissurface not only widens the pores present onthe surface, but also cleans away small bits ofmaterial from the openings. Here is a sampleof dental porcelain that has been etched andmagnified to 200X.

The "cleaning" effect of the acid is evenmore apparent in these two views taken at2,400X (Figs. 3-20, and 3-21).

Fig. 3-20

Fig. 3-21

One might think that the thin fragile projections of porcelainthat cover the surface of the etched porcelain would not havesufficient strength to serve as an anchorage of attachment infusing. It should be remembered, however, that each of theseprojections will be completely surrounded by resin.

As with enamel, there is an optimal period for etching theporcelain. After the optimal period, there is a decrease in themass of the porcelain, but no improvement in the retentivity ofthe surface. The optimal time for etching is dependent upon theconcentration and mixture of acid used as well as the formula ofthe porcelain.

Experience has shown that the optimal time for etching mayeven be partly dependent upon the exact conditions used to firethe porcelain. Fortunately, the bond strength to etched, si-lanated porcelain is so high that even a substantial variation fromthe ideal will still yield results beyond those required by thetechnique. Any bond strength between the composite andporcelain in excess of that between the composite and enamel isunused..

One porcelain manufacturer has specifically formulated aporcelain with components that etch out selectively in order tooptimize the etching technique. Etching provides the mechani-cally retentive portion of the fusing technique on both the toothand porcelain interfaces. The chemical attachment between theresin and both the etched enamel and etched porcelain isafforded through the use of coupling agents. In the case of theporcelain, the usual coupling agent is a silane. There are manybrands of silane currently available in the dental marketplace.Most use either gamma-methacryloxipropyltrimethoxysilane orgamma-Glycidoxypropyltrimethoxysilane.

In the case of the etched enamel, the coupling agent is one ofthe group of "dentin/enarnel bonding agents". Most of thepresent formulations incorporate esters of BIS/gma. Examples ofthis group are Bondlite, Scotchbond, and Sinterbond. Thesepresumably work by forming chemical bonds between the estersand the calcium or phosphate groups of the tooth structure. Thisgroup of coupling agents is extremely suitable for use withporcelain laminates.

On occasion, it becomes necessary to cover over exposeddentin. This could occur, for instance, during a maximum prep,or while covering over a cervical abrasion. While BIS/gma estersare useful for this purpose, several other materials also may beused. These include polyurethane based dentin adhesives, glassi onomer cements, "Bowen's formula" adhesives, GLUMA, andScotchbond2. As always, deep areas of dentin exposure must beprotected from composite resin. Calcium hydroxide is most oftenused for this purpose, since eugenol will inhibit setting ofcomposite resin.

The polyurethane based group is exemplified by DentinAdhesit and Restodent Dentin Bonding Agent. The polyure-thanes are generally created as a condensation polymer betweena polyol (from polyesters or polyethers) and a polyfunctionalisocyanate. The working assumption is that the polyfunctionalisocvanates are responsible for coupling to organic components ofthe tooth surface and composite resin. For maximum effective-ness, it is therefore necessary to have a dentinal smear layer. Ifone is not present during the adhesion process, then it should becreated. Note that since the polyurethane based dentin adhesivesrequire a dentinal smear layer for attachment, they are inappro-priate for use on etched enamel.

"Bowen's formula" adhesives (also known as the oxylate group)have been reported to achieve 1600 psi bond strength to dentin.This is a formidable tenacity, but is achieved only after multipleprocedures that take nearly five minutes to perform.

CHAPTER 3 FUSION: THE BONDING THAT MADE IT ALL POSSIBLE 3 3

Scotchbond 2, consists of a light curedmaterial ("Scotchbond 2") in conjunctionwith a primer ("Scotchprep") (3M, St. Paul,Minnesota). Neither the adhesive nor theprimer individually create any adhesion todentin, but when applied sequentially, theimmediate bond strength is in the region of1500 psi, with a 24 hr. strength of 2700 psi.This compares favorably with the strengthsattainable by bonding to etched enamel (Fig.3-23). One of the major attractions ofScotchbond 2 is its extreme simplicity andease of use.

Fig. 3-22

GLUMA (Columbus Dental, St. Louis, Mo.) is another ex-tremely interesting material for dentin bonding. The techniqueutilizes EDTA, glutaraldehyde, and 2-HEMA in successiveapplications. The bonding is usually explained by the glutaralde-hyde action on collagen in the dentin and copolymerization ofHEMA carbon bonds with the composite resin. One of the mainattractions of GLUMA is the fact that the material and techniquehave been reviewed in the literature since 1984 with consistentlyimpressive results. It was available in Europe for several yearsbefore first becoming available in the United States late in 1988.The clinical technique is simple and reliable.

For cervical abrasion, many operators find it useful to fill in thedefect with glass ionomer cement prior to preparation for thelaminate. Later, when the veneer is seated, the glass ionomer istreated as if it were enamel, with the exception of adjusting theetching time to 20 seconds. While glass ionomer does notproduce as high bond strengths to dentin as Scotchbond2,GLUMA, or the oxylate systems, it does have the decidedadvantage of slowly leaching fluoride to the adjacent toothstructure.

REFERENCES

1. McLaughlin, G.: Porcelain fused to tooth -a new estheticand reconstructive modality. Compend Cont Educ. 5(3):430-436, 1984.

2. Eames, W.B., and Rogers, L.B.: Porcelain repairs: retentionafter one year. Operative Dentistry, 4:75-77, 1979.

3. Nowlin, T.P., Barghi, N., and Norling, B.: Evaluation of thebonding of three porcelain repair systems. J Pros Dent.46(5):516-518, November, 1981.

4. Buonocore, M.A.: A simple method of increasing the adhe-sion of acrylic fillings to enamel surfaces. J Dent Res.34:849-853, 1955.

5. Sebor, Raymond J.: Restoration of class IV lesions andfractures with acid-etch composite. Compend Cont Ed inDentistry. 4(6):510-516, 1983.

6. Calamia, J.R.: Etched porcelain facial veneers: a new treat-ment modality based on scientific and clinical evidence. NYJDent. 53:255-259, 1983.

7. Horn, H.R.: Porcelain laminate veneers bonded to etchedenamel. Dent Clin North Am. 27:671-684, 1983.

8. Horn, Harold R.: A new lamination: porcelain bonded toenamel. NY State Dental journal. 49(6):401-403, 1983.

9. Chalkley, Y.M., and Jensen, M.E.: Enamel shear bondstrength of a dentinal bonding agent. J Dent Res. 63(SpecialIssue A):320, [Abstr. # 1342], March 1984.

10. McLaughlin, G.: Porcelain fused to tooth-a new estheticand reconstructive modality. Compend Cont Ed in Den-tistry. 5(3):430-436, 1984.

11. Gwinnett, A.J.: Normal enamel. 1: Quantitative polarizedlight study. J Dent Res. 45:120, 1966.

12. Ripa, L.W., Gwinnett, A.J., and Buonocore, M.G.: The"prismless" enamel surface-microscopy with polarized light.Dent Radiogr Photogr. 40:38, 1967.

13. Ripa, L.W., Gwinnett, A.J., and Buonocore, M.G.: The"prismless" outer layer of deciduous and permanent enamel.Arch Oral Biol. 11:41-48, 1966.

14. Yedid, S.E., and Chan, K.C.: Bond strength of threeesthetic restorative materials to enamel and dentin. J ProsDent. 42:573, 1980.

15. Young, K.C., et al:ln vitro studies of physical factors affect-ing fissure sealant to enamel. In Silverstone, L.M. andDagon, I.L., editors: Proceedings of the International Symposium on the Acid Etch Technique. St. Paul, Minn., 1975,N. Central.

16. Bergman, G.: Microscopic demonstration of liquid flowthrough human dental enamel. Arch Oral Biol. 8:233, 1963.

17. Hardwick, J. L.: Isotope studies on the penetration of glucoseinto normal and carious enamel and dentin. Arch Oral Biol.4:97, 1961.

18. Dawes, C., Jenkin, G.N., and Tonge, C.H.: The nomencla-ture of the integuments of the enamel surface of teeth. BrDent J. 115:65, 1963.

19. Miura, F.,Kakagawa, K., Ishizaki, A.: Scanning electronmicroscope studies on the direct bonding system. Bull TokyoDent Med Univ. 20:245, 1973.

20. Gwinnett, A.J.: The scientific basis for the sealant proce-dure. J Prevent Dent. 3:15, 1976.

21. Shey, Z., Houpt, M.: The clinical effectiveness of the DeltonFissure Sealant after forty five months. Abstract 642. J. DentRes. 59:428, 1980.

CHAPTER 3 FUSION: THE BONDING THAT MADE IT ALL POSSIBLE

22. Galil, K.A.: Scanning and transmission electron microscopicexamination of occlusal plaque following tooth brushing. JCan Dent Ass. 41:499, 1973.

23. Taylor, C.V., and Gwinnett, A.J.: A study of the penetrationof sealants into pits and fissures. J Am Dent Ass. 87:1181,1973.

24. Pus, M.D., and Way, D.C.: Enamel loss due to orthodonticbonding with filled and unfilled resins using various cleanuptechniques. Am J Orthod. 77:269, 1980.

25. McLaughlin, G.: Direct bonded retainers-the advancedalternative. pg. 13, J.B. Lippincott, Phila., 1986.

26. Schneider, P.M., Messer, L.B., and Douglas, W.H.: Theeffect of enamel reduction in vitro on the bonding ofcomposite resin to permanent human enamel. J Dent Res.60:895, 1981.

27. Black, J.B.: Morphological effect of enamel reduction onbonded veneers. NYS Dent J., 644-646, 1985.

28. Silverstone, L.M.: Fissure sealants. Caries Res. 8:2-26,1974.29.

29. Mardaga, W.J., and Shannon, I.L.: Decreasing the depth ofetch for direct bonding in orthodontics, J Clin Orthodont.16:130-132,1982.

30. Brannstrom, M., Malmgren, O., and Nordenvall, K.J.:Etching of young permanent teeth with an acid gel. Am JOrthodont. 82:379-383, 1982.

31. Barkmeier, W.W., Shaffer, S.E., and Gwinnett, A.J.: Ef-fects of 15 vs 60 second enamel acid conditioning on adhesionand morphology. Oper Dent. 11:111-116, 1986.

32. Oliver, R.G.: The effects of differing etch times on the etchpattern of unerupted and erupted human teeth examinedusing the scanning electron microscope. Br J Orthodont.,14:105-107, April, 1987.

Fig. 4-2

Hypocalcification. The so-called white"discoloration", these spots can be as per-plexing to the patient and dentist as staining.

Fig. 4-3

Diastemas. These are frequently seen inpatients whose jaw and teeth sizes do notmatch. The mandible may be too large, orthe teeth may be too small, or possibly acombination of both. There may be anteriorspacing due to early loss of the posteriorteeth and the subsequent drifting.

Fig. 4-4

Peg laterals. These malformed incisorsoccur relatively frequently, often being seenin patients who have congenitally missingteeth and the related problems of diastemas.Peg laterals are hereditary, and if a patient isaffected, it is likely that his siblings willrequire treatment also.

CHAPTER 4 PORCELAIN VENEERS: INDICATIONS AND CONTRAINDICATIONS 39

Chipped teeth. This kind of breakdown

may be attributable to external influences,

such as sports or fights, or to intraoral forces,such as bruxing, grinding, and clenching.

r ig. 4-5

Rotated teeth. These teeth erupt or grow

incorrectly, often as a result of crowding

during the mixed dentition period. Their

cosmetic treatment will sometimes include

the use of orthodontics.

Fig. 4-6

Lingual position. These malpositioned

teeth are most often corrected orthodonti-cally, but can be treated with porcelain ve-

neers as well.

Fig. 4-7

Fig. 4-8

Stained restorations. Composite restora-tions may be acceptable dentally, but notesthetically. For patients who smoke, ordrink coffee or tea, replacing these with newcomposites is often at best a short termsolution.

Fig. 4-9

Foreshortened teeth. Some patients haveworn away some part of their incisorsthrough clenching or grinding. Once theproblem of decreased vertical dimension hasbeen attended to, these anteriors can beesthetically restored.

Fig. 4-10

Malpositioned midlines. In cases wherethere is a moderate amount of midline dis-placement, especially when this is associatedwith diastemas, porcelain veneers may be adesirable treatment modality.

Toothbrush abrasion. The non-invasivenature of veneering, and the resistant surfacepresented after treatment, make porcelainveneers the restoration of choice.

Fig. 4-11

Worn acrylic veneers. There are manypatients who have preformed plastic veneersbonded to their teeth. Unfortunately, pre-formed plastic laminates have a relativelyshort esthetic lifetime in the mouth. Whenthe positive esthetic effect of the plasticveneer is lost, these patients become idealcandidates for porcelain laminates.

Fig. 4-12

Bonding to existing bridges. Silane fusionallows dentists to bond veneers to both por-celain fused to metal and acrylic veneerbridges. Porcelain laminates thus can beutilized to replace worn or chipped facings onexisting bridges. At present, this use is con-sidered a compromise to replacing the entirebridge and should not be considered a per-manent solution.

Fig. 4- 13

Fig. 4-14

Missing lateral incisors. This commonproblem is often solved by disguising thecuspid as a lateral incisor. Since the facialaspect of the premolars exhibit caniniformanatomy, the result can be esthetically dra-matic.

CONTRAINDICATIONS

There are also a few contraindications for the use of porcelainlaminates. These contraindications include the following:

Fig. 4-15

Insufficient fusible substrate. The tech-nique used to attach porcelain veneers toteeth has always been most effective withetched enamel. Adequate attachment alsohas been effected over roughened composite.In the past, the bond strength to dentin hasnot been considered high enough to warrantthe placement of a veneer in the absence ofenamel. With the current emergence of thenewer dentin bonding agents such asGLUMA (Columbus Dental, St. Louis, Mo.)and Scotchbond II (3M, St. Paul, Minne-sota), this contraindication may already havebeen eliminated.

Labial version. Teeth that are positionedlabially to the arch contour beyond the rea-sonable depth to which preparation can betaken traditionally have not been veneered.The anticipated bond strength to dentin hasalways remained below acceptable levels forthis technique. As already indicated, it ishoped that with the new generations of den-tin bonding agents this restriction will belifted. Until such time, however, we wouldcontinue to recommend that whenever pos-sible such cases should be treated orthodon-tically.

Fig. 4-16

Excessive interdental spacing. This typeof situation does not allow full closure of thespaces without creating another estheticproblem-oversized looking teeth. Porcelainlaminates can still be used to improve theesthetic situation, but the experienced Cos-metic Dentist will leave some interproximalspace.

Fig. 4-17

Poor oral hygiene. The lack of home careis a contraindication to any type of majordental restorative work, including veneers.

Mouthbreathing. When mouthbreathing is present, there is arelatively poor prognosis for the case due to both the eventualdecay under the veneers and the potentially shortened lifespan ofthe materials themselves. The materials experience greaterstresses when they are constantly wetted and then desiccated.The dentist, therefore, has a duty to inform certain patients withhigh lip lines that they do not present ideal oral conditions forporcelain veneers, and the long term prognosis must be guarded.

Some contact sports. Chipped anteriors are sometimes theresult of playing various sports without a protective face ormouthguard. If the patient cannot be induced to change hishabits, or to at least protect his teeth, veneers are not indicated.

Clenching or bruxing. Clenchers and bruxers are sometimespoor candidates for porcelain veneers for a perhaps surprisingreason. Porcelain veneers that extend over onto surfaces whichcome into contact with the opposing dentition may fracture, butit is more likely that they will wear down any opposing naturalteeth creating accelerated wear.

Extreme midline deviation. In those few cases where one ofthe upper central incisors actually straddles the midline, lami-nate veneering is not a good solution to the problem. Sinceveneering cannot create an embrasure or interdental space in themiddle of a tooth, it is not reasonable to undertake laminatetreatment where esthetic results are unlikely to be achieved.

THE SMILE ANALYSIS

Obviously, the first step in the fabrication of porcelain veneersmust be to establish the need for this kind of restorative work andthe conditions upon which ultimate success (or failure) will bepredicated. If all that is being considered is a single tooth, thereis no need for a complete smile analysis. In such cases, theporcelain laminate must be designed to fit harmoniously with theexisting dentition. When restoration of a larger section of thedentition is considered, however, the initial evaluation should bethe smile analysis. This should be done to help both the dentistand patient examine the general problems that exist and thepotential for their solution.

Perhaps in the field of cosmetics more than in any other areaof dentistry, it is easy for the dentist to misinterpret the desiresof the patient. The patient has little or no knowledge of dentistryand is thus often unable to clearly define his dental goals, orsometimes even what is currently disturbing him. Therefore, theauthors suggest regular use of a short but comprehensive ques-tionnaire to help identify and isolate both the problems and themost acceptable treatment goals.

Our questionnaire has been designed with two convergentareas: patient and dentist objective considerations, and patientand dentist subjective considerations. In the former, the dentistis more important because he is the one trained to observe andanalyze oral conditions. In the latter, the patient's concerns areparamount because he will be wearing the final product.

OBJECTIVE EVALUATION

The objective evaluation is begun by comparing the shape andthe size of the teeth in relation to the shape and the size of thehead. Current esthetic standards lead us to expect a visualcorrespondence between these two structures. For example,today's cosmetic standards lead us to expect long, narrow teeth tooccur more frequently in dolicocephalic patients (and, con-versely, we would also expect that someone with a wide, roundface is likely to possess wider, less angular teeth). This perceivedcosmetic relationship is particularly important for case planningwhen multiple spaces are present, since in such cases the dentistcannot use any existing anterior teeth to estimate the requireddimensions.

There is a readily available method ofquantifying this analysis in a reproduciblemanner, which is in turn easy to transmit toa laboratory. A number of years ago, theDentsply Company created the TrubyteTooth Indicator (L.D. Caulk Co., Milford,Delaware). While this system was intendedto help select properly proportioned anteriorteeth for dentures, it can guide the choice ofboth shape and size in the veneer reconstruc-tion of a smile. An added benefit of utilizingthis system is that laboratory technicians,already familiar with denture tooth selection,can readily comprehend and duplicate thetype of appearance requested by the dentist.

Fig. 4-19

It is important to remember that this system is but a guide.The dentist must always exercise artistic control in order toachieve the maximum improvement in esthetics.This systemclassifies faces into four basic typical forms: Square, SquareTapering, Tapering, and Ovoid (See Fig. 4-20).

There is a further modification of the first four categories by anadditional Ovoid influence (See Fig. 4-21). A basic assumptionbehind the tooth indicator is that if the face and teeth are inharmony, then a more pleasing esthetic condition results. Thereis no intention here to indicate that the teeth are, or even shouldbe, always related to the proportions of the face. However, if theresult of this type of evaluation leads to a more pleasing visualimpact, then it cannot be ignored in dental cosmetics.

43 COLOR ATLAS OF PORCELAIN LAMINATE \ I \I

The plastic plate is placed in front of apatient's face, with the nose poking throughthe specially provided triangular space . Theeyes are lined up in the special slits provided,and the mouth is centered. Then, lookingfrom straight ahead, the dentist can deter-mine the shape of the face. It is helpful at thistime to utilize the vertical guidelines in theplastic face plate. Because these lines clearlydelimit various portions of the face, they areparticularly useful in trying to decide border-line cases. In short, the face plate helps tofocus the dentist's attention on the details heis seeking and tends to eliminate most of theextraneous input that might make this eval-uation more difficult.

r ig. 4-22

The shape of the face also tends to influence the ideal relativeconvexity (or concavity) of the maxillary central and laterals. Thisis an area often overlooked by both dentists and technicians, andwhile such an oversight is not a glaring error, it certainly can haveenough of an effect on porcelain veneers to make them appearless lifelike.

The facial shape should be entered on the Smile AnalysisForm. Combined with later data on the mesio-distal and verticalspace available, the shape will assist in the generation of thespecific personalized "mold" to be fabricated.

Fig. 4-23

The number of teeth exposed to view onsmiling will indicate how far distally thedentist should be placing veneers. While it isgenerally accepted that in order to ade-quately improve the smile, at least the ante-rior six maxillary teeth should have veneers,this is plainly not enough for someone whoshows the second bicuspid. All the maxillaryteeth that are apparent on a regular smileshould be treated. While this may sound likea make-work suggestion, the dentist mustconsider the final result. A patient who hashad his six anteriors covered with porcelainveneers may find that his untreated firstbicuspids, now particularly unesthetic incomparison with the treated teeth, stand outmuch more than previously when he smiles.

In a case where one of the bicuspids islingual to the arch, for instance, placing aveneer on the adjacent cuspid will increasethe apparent malposition of the bicuspid.Therefore, if possible the bicuspid should becovered as well.

Fig. 4--24

For patients seeking partial or incomplete treatment, thisproblem must be pointed out, or they will be very disappointedin the results. In fact, the dentist should allow the patient, withthe help of a mirror, to actually select just how far back theveneers will be done. It is likely that the patient will opt for moreteeth than the dentist might have chosen.

The next point of observation is the maxillary high lip line. Afull or even a lower than normal lip is of no great importance, buta raised high lip line may lead to many difficulties. In these casesthe location and the finishing of the gingival margins of theveneers is even more critical than usual. The slightest imperfec-tion or incomplete masking will be readily visible, especially tothe patient's eye. Sometimes the only method available to correctan irregular set of gingival margins is with surgery.

With normal lips, these areas are usually hidden, exceptingthose instances where extreme muscular movements occur. Inthe high lip line patients, the gingival margin of the upperanteriors is often the visual focusing point. In any case, it is vitalthat this observation be made before starting the case. A mistakein planning at this point cannot be compensated for after the caseis fused in place.

Fig. 4-25

Another major concern in these patients isthe shape and the size of the interproximalspaces. These are the hardest areas to finishveneers in such a way that they both coverthe underlying tooth completely and areesthetic and anatomically correct in theirown right. A mistake often made by thosejust beginning to work with porcelain ve-neers is to make the teeth quite square, andthereby close off much of the interproximalspaces. In a high lip line patient this can bedisastrous; the teeth look enormous and un-natural, the so-called "horse-teeth".

Another consideration found with somehigh lip line patients is that there is often anassociated tendency toward mouthbreathing.

Fig. 4-26

Misaligned teeth may or may not hinderthe placement of veneers, depending on thedirection and the degree of misalignment. Alateral incisor in slight linguo-version caneasily be built out to the arch contour with aslightly thickened veneer assuming there isadequate mesio-distal clearance (Figs. 4-26,4-27).

Fig. 4-27

CHAPTER 4 PORCELAIN VENEERS: INDICATIONS AND CONTRAINDICATIONS 5 1

But a mandibular cuspid in crossbite oftenlimits treatment. If the tooth to be treated isin crossbite, orthodontics may be requiredprior to cosmetic restoration.

In certain orthodontically classified condi-tions, such as a bimaxillary protrusion, or aClass II malocclusion, where the maxillaryanteriors are already positioned too far labi-ally, adding the bulk (however minimal) of aporcelain veneer will cause a more accentu-ated esthetic problem. Obviously, this char-acteristic must be discovered and discussedwith the patient at this time.

Fig. 4-28

Some patients' teeth may have wear facetsor even chipping. While these conditionsmay be minor and not contribute greatly tothe esthetic problem, they may be indicativeof underlying situations that contraindicatethe placement of veneers. Both wear facetsand chipping can be the result of a loss ofvertical dimension in the posterior region. Ifthis loss cannot be corrected first, then it isunlikely that veneers will succeed in the longterm, for they will be subject to the intenseand continuous occlusal forces that broke thenatural teeth initially.

Fig. 4-29

Any chipped or broken teeth should be noted at this time, aswell as the reason for the breakage. If the cause for thedestruction cannot be alleviated or at least modified, then thereis little hope the porcelain laminates will survive.

Finally, the dentist must evaluate the color and staining of theteeth. This is important for the dentist to understand thedifficulty of the ensuing project. The ideal situation for porcelainlaminates occurs when the color does not have to be changed.The next most desirable category occurs when the colors of all theteeth have to be changed equally and not greatly. As the tint hasto be lightened more, the work becomes more difficult. Thehardest situation is one in which the teeth are various differentdark shades and they all have to match in the final product.

When determining the final shade for the maxillary anteriors,the dentist should take into consideration the shade of themandibular anteriors. If the difference in shade between the twoarches is too great, the esthetic result will not be pleasing; adecision must be made either to veneer the lower anteriors aswell, or to make a less dramatic alteration in the maxilla.

Natural characteristics of the patient's own dentition, such astranslucency and shade gradation, should be incorporated intoveneers whenever possible and desirable. Such qualities cangreatly enhance the final appearance of a veneer. In order toinsure harmony with the remaining unlaminated teeth, thedentist should make several observations about the naturalteeth's shading. What is the degree of incisal graying (translu-cency)? Is the degree of coloration near the cervical a normalamount? Are there any unusual characterizations present, such ascraze lines, hypoplastic areas, maverick colors, etc., which wouldbe desirable in the final laminate? A conscientious dentist,working with a competent laboratory technician should have fewproblems including the above features. (see chapter 7)

Mesio-distal Space Analysis

Once the operator has established the facial factors that willgovern the overall shape and size of the anterior teeth, it remainsto be established that the required space is available and that theveneers can be placed in such a manner as to ensure an estheticresult.

The first guiding figure is the total suggested space for the sixmaxillary anteriors, determined by using the Trubyte BioformSystem of Face and Tooth Form Harmony. This "ideal" width iscompared to the space actually available in the mouth, usingeither the distals of the cuspids or the mesials of the firstbicuspids as a reference point. These measurements will enablethe dentist to determine the need for larger or smaller teeth.

Fig. 4-:30

Under certain circumstances, the operatorcan physically alter the size of the teeth (bymaking the veneers wider, for instance),while in other cases he has to rely on thetechnician's capacity for creating illusions inthe porcelain laminates.

CHAPTER 4 PORCELAIN VENEERS: INDICATIONS AND CONTRAINDICATIONS

The second factor that is important in this analysis is the"ideal" width of the central incisor in proportion to the width andcontour of the face. The dentist might need to increase the widthof the central (and then the other interiors correspondingly), andthis measurement will indicate just how wide the tooth can bemade before it will look out of proportion with respect to the face.An analysis of this type will indicate, before treatment is begun,whether the diastemas should be closed completely.

It is very important in terms of cosmetic appearances toestablish the correct location of the midline. The midline,between the two upper central incisors, has two reference points:the midline of the facial features (eyes, nose, lips), and themidline of the lower anteriors. When the maxillary midline ismalpositioned, the entire face seems to be unbalanced. It istherefore, very important to respect the existing midline if it is inthe proper location, and if it is not, to recreate an estheticappearance by placing it correctly. The maxillary and mandibularmidlines should be aligned, and both, in turn, must follow thefacial lines.

A difficulty arises when the facial and mandibular dentalmidlines do not coincide. The dentist is faced with a dilemma;whichever alignment he chooses will leave a partially unestheticappearance. The solution is not to place the maxillary midline inan intermediate position, as this would only compound theproblem. The maxillary midline should always be aligned withthe facial midline, as these are the two most readily visiblelandmarks.

Placing the maxillary midline out of thefacial midline will often give the patient anunidentifiable (by non-dentists) but never-theless skewed appearance. In contrast, themalpositioned mandibular midline will behidden by either the lower lips or the maxil-lary teeth most of the time. In this situation,obviously, a compromise solution must beemployed.

Fig. 4- 3 1

It is sometimes preferable for the patient to have orthodontictreatment to align his teeth. Naturally, this solution requirestime and the willingness of the patient to wear orthodonticappliances. Unfortunately, many patients seeking cosmetic treat-ment are also seeking to avoid intraoral appliances. Sometimes,however, acceptable esthetics simply cannot be obtained withoutsome tooth movement, and the use of orthodontics and porcelainlamination act in symbiotic fashion to achieve the patient'sdesired esthetic results in a minimum amount of time.

Fig. 4-32

Symmetry in a smile goes beyond havingthe right number of teeth on each side of themidline. Generally, the corresponding teethon either side of the arch are similar in size.Any divergence from this balance is observedas an unesthetic feature. Prior to treatment,the dentist must evaluate whether the con-tralateral teeth are dimensionally balanced.In the case that they are not, he must makesure that there is enough spacing available torestore this balance. If the mesio-distal spac-ing is unavailable, it should be created by aminimum amount of judicious preparation.

Rotated teeth present a problem in veneering only to theextent that they protrude from the arch contour and presentmesio-distal size discrepancies when viewed from the labial. Anyportion of the rotated tooth that is labial to the normal facialcontour of the arch should be reduced; otherwise, the coveringporcelain veneer will protrude in an unappealing manner. Caremust be taken to ensure that this preparation does not removeexcessive tooth structure; if the reduction involved is very deepinto the dentin or the pulp, then obviously this treatmentmodality is not the one of choice.

If a lateral is rotated 90 degrees with no spaces present on themesial or distal, then, by virtue of the dimensions bucco-linguallybeing less than those mesio-distally, there will be inadequatewidth to place a normal looking lateral veneer. If there is nospace available in the arch, then either preparation of theadjacent teeth or illusion creating techniques must be employedto correct this feature (see chapter 9).

Another possible problem of rotation is a cuspid in a similar 90

degree position. Here the problem is reversed. The bucco-

lingual dimensions of the cuspid are greater than the mesio-distal

ones. Therefore, the veneered cuspid will appear too wide. Thiscannot be corrected by the reduction of the cuspid's dimensions

because this kind of preparation would destroy the interdental

contacts and upset the occlusal harmony of the entire mouth.

Fortunately, by adjusting the labial prominence of the cuspid

more mesially or distally, the apparent size can be controlled (see

chapter 9).

Vertical Space Analysis

Once the dentist has analyzed the facial form and the mesio-

distal influences that contribute to the porcelain veneer design,

there remains one additional dimension that requires parameter

definition before the procedure can be started.

The Bioform Tooth Form System gives a reading for the

approximate vertical height of the central incisor. This figure, in

millimeters, refers to the enamel portion of the crown from the

incisal edge to the cervical dentino-enamel junction at the

mid-point of the tooth. This dimension, along with the previously

established central incisor width and facial outline form, gives atotal picture of a tooth (and hence the entire anterior region) that

is in esthetic harmony with the patient's face.

If there is adequate vertical space to allow the required length

for the incisors, then the fabrication of the veneer is straightfor-

ward. Should the necessary space be lacking, the laboratory will

have to resort to lengthening the teeth (or shortening them, as

the case may be) through illusion (see chapter 9).

Many patients would like a younger ap-

pearance and this is often one of their mainreasons for seeking Cosmetic Dental treat-

ment. One important method for achieving

this is to make the central incisors slightly

longer than the maxillary lateral incisors.

Fig. 4-33

Fig. 4-34

Generally, older teeth look worn at theincisal edge and have been ground down to aflat plane. The easiest method of reversingthis is to lengthen the centrals (provided thisdoes not interfere with excursive and protru-sive movements).

Occlusal interference with the lower incisors could be verydamaging. The porcelain of the veneers will abrade the enamel ofthe mandibular teeth if they are in excessive contact, particularlyif the glaze has been removed from the porcelain during finishingprocedures. The dentist also must evaluate the potential forexcessive contact in extreme protrusive movements. While this isnot a likely excursion for the patient, even a single occurrencecould fracture a veneer that has too little vertical clearance and aweak incisal edge. Under usual circumstances there should be nohesitation in allowing normal occlusion on the porcelain, includ-ing porcelain that is brought over the incisal edge.

Subjective Evaluation

Once the dentist has had a chance to evaluate all of the above,he will want to find out what the patient's overriding concernsmight be.

People are most concerned about the color of their teeth.Often even perfectly healthy, esthetic teeth are deprecated fornot having the "Hollywood Look". Due to many years ofreinforcement by television advertising, most patients think theirteeth are too yellow. Therefore, the first question asked to thepatient often should be "How do you feel about the color of yourteeth?". The manner and content of the patient's answer will givethe dentist important clues as to the potential for successfultreatment. The less realistic a patient's self-evaluation, the morelikely that he will be dissatisfied with treatment, no matter howgood the result may be. The pickier he is with minor, non-contributory details, the harder he is going to be to please. Thecloser that he holds the mirror to his mouth before treatment, thecloser his inspection after treatment.

The dentist must also determine whether the concern with thecolor (or appearance) of the teeth is the genuine problem. Itmay be the outward manifestation of some deeper psychological

CHAPTER 4 PORCELAIN VENEERS: INDICATIONS AND CONTRAINDICATIONS

difficulty. While most dentists have inadequate analytical knowl-edge to determine this accurately, they usually have enough"people skills" to sniff out unsuitable patients.

Many people view diastemas as undesirable, so when diaste-mas are present, this should be another area of discussion. Thepatient will answer very readily whether or not the spacesbetween the teeth bother him. Most often the response will beaffirmative; the spaces make him feel less assertive or lessconfident, or unwilling to open his mouth to smile. Since thisparticular dental problem is relatively easy to eliminate withveneers, the long term prognosis is excellent unless the diaste-mas are unusually large.

The size and the shape of the teeth are also of concern. Onecommon problem is the peg lateral. In such cases all the teeth arewell formed and positioned except for two right in the front of themouth. Obviously this situation is often distressing, and thepatient should be encouraged to express his feelings on thesubject. Many people also complain of disproportionately smallteeth, since these result in the formation of spaces. Thankfully,these situations are often ideal for porcelain veneers.

Finally, there are a series of points to make to the patient withregards to his appearance that will firmly clarify in his mindwhether there is a need for treatment.

First, ask the subjective question: "Would you feel moreconfident if your smile was improved?". Of course almost anyonecan answer "yes" to this question. In answering, a patient usuallywill reveal where he hopes his improved appearance will have itsgreatest impact. This can help the dentist to tailor the treatmentmore specifically.

Next: "What appearance would you like?". By specifying theultimate goal, the patient is focusing both the dentist's and hisown attention on a reproducible model. Thus guided, the dentistcan attempt a close approximation, resulting in less frustration forhim and greater patient acceptance. Ideally, the patient canbring in a picture of how he would prefer to look. This commu-nication can be augmented through the use of diagnostic wax-upsto be discussed shortly and computer imaging (chapter 8).

It is very important at this stage to involve the patient activelyin goal selection and treatment planning. As an informed patient,he will cooperate and appreciate the treatment much more thana patient who is not at all involved with his own smile analysis.

The Diagnostic Wax Up

The importance of communication simply cannot be overem-phasized. If the dentist does not clearly understand the patient'sobjectives, then it will merely be by chance alone that theexpectations are fulfilled. Many times, words will suffice to createa full communication between the parties-but in many caseswords are simply not enough. The dentist and patient often donot share a common language when it comes to the details ofteeth. In these situations, more is needed.

Three devices have been used to help bridge the gap. Photo-graphs are often used to allow the patient to see what the dentistis describing and to allow the patient to show the dentist what hewants. (This modality is more thoroughly discussed in chapter 8.)

Photography can pass from a static to a dynamic tool whencombined with the power of computers. This mix can beespecially powerful, since the anticipated changes in the patient'ssmile can be seen as if in final form, including the full face of thepatient. (This exciting modality is also discussed in chapter 8.)

Still, as tantalizing as the photographic possibilities are, theimages remain only two dimensional. At present the onlythree-dimensional tool we have at our disposal is that of thediagnostic wax-up. In certain cases, dentists may find it necessaryto use diagnostic wax-ups for their own planning purposes. Whilewith time and experience, most practitioners will be able tovisualize the final esthetic result, the dentist, the technician, andthe patient can all benefit from the foresight and clarity ofcommunication provided by pre-treatment wax-ups.

In the end, the patient has the most to gain. He has the leastcapacity of anticipating both the advantages of treatment and thelimitations that exist in his particular case. A verbal explanationby the dentist may create, in the patient's mind, an entirelydifferent picture from what the dentist is trying to convey.Similarly, the patient's description of the desired results can bemisunderstood by the dentist. A pre-treatment consultationincluding a wax-up will demonstrate exactly what is possible andwhat is not. The patient will have realistic expectations for thetreatment, and this alone may avoid subsequent dissatisfaction.Since the patient has an opportunity to preview the treatment,he may have some very important contributions of his own tomake. There often are aspects of esthetics that may be of greatconcern to the patient, and yet, due to the fact that they may beof little dental consequence, the dentist may not be sensitive tothem. Here, a word to the dentist will allow him to change thebothersome features, thereby ensuring a more acceptable out-come. In addition, making the patient a part of the treatmentprocess lets him feel more positive about the final result.

By utilizing the diagnostic wax-up, the dentist will have had anopportunity to evaluate both the approximate final result and theproblems that may arise. It may be decided on the basis of thewax-ups that more space is required and that more toothstructure will have to be reduced, or that it is impossible to closethe existing diastemas without enlarging the teeth beyond nor-mal mesio-distal proportion. The practitioner may find that thepatient's requests are unreasonable, in which instance it may beadvisable to drop the case if the demands cannot be modified toan acceptable level.

In addition, communication with the laboratory technician isnot always one hundred per cent clear, and it is much better forthe dentist to find the gremlins at this stage of treatment thanwith the final porcelain. In short, problems are much more easilyhandled in wax than in veneers.

Wax-ups also can be a boon to the technician. Since there is avery clear model of what is desired by both the dentist and thepatient, the element of guesswork is eliminated. The laboratory-fabricated porcelain veneer is ideally fused on to the tooth withminimal adjustment and polishing; therefore, if the techniciancan create a very close to ideal veneer based upon the correctedwax-up, the dentist will have a much easier procedure intra-orally. Of course the number of remakes is considerably reduced.

The wax-up can be prepared by either the laboratory or thedentist. If the technician does the work, there will be an addedcharge, but this is negligible with respect to both the total pricecharged for the veneers and the number of problems that can beeliminated.

The wax-up should be done in tooth col-ored wax.

Fig. 4-35

While dental professionals may be able toappreciate a blue, green, or multi-hued waxtooth, it is unlikely that the patient will sharetheir appreciation. A dentist who doespresent a case in such a colored wax may findhimself explaining for extended periods howthe final porcelain will be tooth shaded andnot blue.

Fig. 4-36

One area that cannot be previewed with a wax-up is the colorchange that may be effected with porcelain veneers. The patientmust be told repeatedly that the color is only that of thediagnostic wax and that the porcelain will be much more true tolife.

Interestingly, while the diagnostic wax-up is intended to be acommunication tool, it also seems to act as a motivator. Theauthors have noted that in some cases when the patient wasconsidering treatment but was not yet fully committed, wax-upshave had the effect of tipping the scales in favor of treatment.

Fig. 4-37

This patient, for instance, was not sure thatveneers could help her appearance, and shewas afraid that the teeth would be too big.She initially asked for veneers only on thecentrals.

Fig. 4-38

Models were taken and sent to the labora-tory for diagnostic wax-ups. The technician,following the guidelines from the dentist,began to reshape the teeth. Before showing itto the patient, the diagnostic wax-up shouldbe clean and free of any extraneous wax ormaterial that will detract from the clarity ofpresentation.

The before and waxed-up models were shown to the patient.The dentist evaluated the esthetic result and considered theinput from the patient. On examining the wax-up, this patientchose to have four veneers instead of two. The dentist made thenecessary adjustments in the wax-up model and then proceededwith tooth preparation. Then the impressions and wax-ups wereboth sent to the laboratory.

This finished case demonstrates what is insome aspects a compromise treatment. Butsince the patient was aware of the limitationsbeforehand, she was pleased with the results.

Fig. 4-39

Fig. 5-1

Most of these rules are fully self-explanatoryand thus need no further clarification. Rulenumber eight, however, is perhaps the onemost often neglected. It is extremely com-mon to place veneers that seem to cover allvisible areas when viewed directly from thefront of the tooth, but which fall short of themark when seen from an angle. Such is thecase in this example. The laminate on theright lateral incisor covers most of the facialareas adequately, but the proximal areas nearthe gingiva are exposed. Often these areasare adequately hidden with composite at thetime of fusing, but after a few years the errorin design becomes glaring.

Fig. 5-2

This pitfall can be avoided easily enough,but it requires an acute sensitivity to theproblem during preparation and fabrication.Before preparation, the dentist must makesure that there is a path of insertion free fromundercuts that allows porcelain to cover allareas visually accessible from any angle. Thisrequires careful observation of the tooth be-ing laminated from various extreme angles todetermine which areas of the tooth are opento view. Only then should the dentist beginany preparation of the tooth. A mistake at thisstage cannot be rectified later. Similarly, afailure in the design stage by the laboratory isuncorrectable later. In some cases the inter-proximal design must be as aggressive asshown here.

CHAPTER 5 TOOTH PREPARATION FOR PORCELAIN LAMINATE VENEERS 65

VENEER MARGIN PLACEMENT

Because of the requirements of crown and bridge technique,we have become used to routinely locating margins subgingi-vally. While it is readily accepted that this placement is lessdesirable from a hygienic point of view than a supragingival one,the demands of esthetics are respected. As procedures have beenmodified, and as new techniques have been introduced, dentistshave clung to certain habits without questioning their currentvalue. It is obvious that porcelain laminates are quite different inmany respects than conventional crowns. We must thereforeapproach the question of margin placement of porcelain veneerswith an open mind, unclouded by what we have learned for otherrestorative procedures.

When dealing with margin placement, thefirst consideration is the micro-environmentof the margin.

Fig. 5-3

There is, ideally, some gingival enamel that, through the useof a composite bonding agent and a silane coupler, is fused to aknife-edge porcelain margin. The enamel certainly has no poten-tial for gingival irritation, and porcelain has shown itself to bevery bio-compatible. The only potential problem in this micro-cosm is the composite bonding agent. The thickness of this layeris kept to an absolute minimum through the use of preciseimpression, laboratory fabrication, and seating techniques. Butno matter how careful the operator is, there will be a narrowband which could potentially cause gingival irritation and subse-quent recession. The only method which can minimize theseharmful periodontal effects, is the supragingival placement of themargin. Where the composite bonding layer cannot come intointimate contact with gingiva, it will not cause irritation.

66 COLOR ATLAS OF PORCELAIN LAMINATE I :l I

This solution raises the question of esthetics. After all, mostpeople treated with porcelain veneers are seeking, above all,cosmetic help.

The reason given by some operators for subgingival placementof porcelain laminates is to conceal the margin of the laminatefrom view. In fact, concealment is not a problem for most teeth.Since the gingival margin of the veneer can be made with a knifeedge, the supragingival veneer margin is blended into thegingival enamel with a color gradient. As the porcelain becomesthinner and thinner toward the gingival margin, its capacity tomodify the underlying inherent color decreases. Since thecomposite bonding materials have a minimal shade maskingeffect in their ideal thickness, their contribution to color at thegingival area is negligible.

Fig. 5-4

Thus we have a gradual, lifelike, colorgradient readily established. The margin willnot be noticed, even in full view, becausethere is not an abrupt change. While on closeinspection, the gradient can be seen, theactual position of the well-finished margin ishidden.

In cases in which maximum hiding of the natural tooth shadeis necessary, this gradual blending of shade is not desirable. Insuch situations, the dictates of esthetics demand gingival prepa-ration. Fortunately, this is not the usual situation.

Another problem inherent with subgingival margins is thedifficulties in creating a dry field for fusing in the gingival sulcus.While it is theoretically possible to do so, from a purelypragmatic point of view, this goal is rarely attained. If fusing isattempted in a wet field, it is doomed to failure, inevitablyresulting in leakage and staining under the gingival margin of thelaminate.

The choice of the supragingival margin makes taking animpression an easier and more predictable phase of the proce-dure and allows the laboratory that much more ease in thecorrect fabrication of the veneer.

It is, of course, desirable to maintain thenatural emergence angle of the tooth as muchas possible. If the contour of the facial aspectmust be changed, the further from the gin-giva that this change occurs, the less likelythat food will become trapped and causeirritation.

Fig. 5-5

The important point to remember here, however, is thatwherever the laminate ends, the requirement for patient hygienemust not be violated. The ability or inability of the patient toclean the gingival sulcus is the final criterion as to the acceptableemergence angle. In some cases, due to the angle and position ofthe veneered tooth, it is possible to create a large change in theemergence angle without compromising the cleansability of thesulcus. In these cases, the periodontal health of the surroundingtissues will be maintained.

PREPARATION TYPES

With these factors in mind, here are the six basic preparationtypes:

Type I. Minimal Preparation. This prep-aration type is well described by its name. Ina minimal preparation, no tooth reduction isundertaken except for that necessary to pro-vide a path of insertion that is free fromundercuts. Often this means that no prepa-ration is necessary.

Fig. 5-6

Fig. 5-7

Provided that the increased prominence ofthe veneered tooth is not a problem, thetooth need not be reduced at all.

Fig. 5-8

Often, however, some slight preparation isneeded to create a proper path of insertion.Such is the case when gingival recession hasuncovered the interproximal tooth structure.Since many teeth display a slight concavityon their proximal surface, it is often neces-sary to slightly reduce the proximo-facial lineangle near the gingival margin. (Note: In allthe schematics used to illustrate the prepa-ration types in this chapter, the areas withstripes indicate places where reduction of thetooth surface may be desirable. The stippledareas represent porcelain.)

Fig. 5-9

This results in a veneer which comes to aknife edge on all its margins.

Such was the case for this patient who hadreceived preformed plastic laminates just twoyears earlier (see Figs. 2-11, 2-12, and 2-13).The plastic laminates were obviously of onlylimited success.

Fig. 5-10

Because of the position of the teeth, theirshade, and their contour, absolutely no prep-aration of the teeth was required to achievethis very pleasing result in porcelain. Theselaminates have served for over five years atthe date of publication of this text.

Fig. 5-11

70 COLOR ATLAS OF PORCELAIN LAM I \ A I E N h:\EERS

Fig. 5-12

Another typical case requiring minimal orno preparation is shown here (Figs. 5-12,5-13)).

Fig. 5-13

Four veneers were used, and the onlypreparation required in this case was toslightly reduce the prominence of the disto-incisal corners of the two central incisors( Figs. 5-14, 5-15).

Fig. 5-14

Fig. 5-15

Type II. Incisal Preparation. On occa-sion, for reasons of shade control, it is advan-tageous to have a greater thickness of porce-lain at the incisal edge than at the knife edgedfinish line provided by the Type I prepara-tion. In these cases, it is suggested that thedentist cut into the incisal edge in such a wayas to allow for an even thickness of porcelainas the incisal edge is approached. This iseasily achieved with a cylindrical instrument,such as a 556 bur or a diamond cylinder. Thedentist should be aware of the direction ofthe enamel prisms to avoid undercuttingthem.

Fig. 5-16

72 COLOR ATLAS OF PORCELAIN LAM IN ATE ENEERS

Fig. 5-17

As in the Type I preparation, the dentistmay find that slight judicious grinding at thegingival third of the facio-proximal line anglewill be helpful in creating an undercut freepath of insertion.

Fig. 5-18

A clinical example of the Type II prepara-tion is shown in the next three figures. Hereis how the teeth looked before preparation.

Fig. 5-19

In this figure the two central incisors havebeen prepared for the laminates: Normally,the Class III restorations would have beenreplaced with bonded restorations prior topreparation. In this case, however, the ClassIII restorations were replaced at the time offusing.

CHAPTER 5 TOOTH PREPARATION FOR PORCELAIN LAMINATE VENEERS 7 3

The two laminates were fused into place atthe next visit, and this photograph was takenimmediately after fusing. Notice that there isno tissue blanching at the gingival margin,despite the fact that there was no toothreduction in that area.

Fig. 5-20

Type III. Over the Incisal Edge. In this design, the porcelainextends beyond the incisal edge. If the tooth is already short-ened, then all that is needed is to ensure that there are no sharpangles protruding from the tooth in the areas where the veneeris to be placed (including the inciso-proximal angles) and to becertain that the path of insertion is free from undercuts. Inaddition, the margin of the veneer should terminate on enamel ifat all possible. Often this means a slight reduction of the lingualaspect of the incisal edge to make room for the porcelain.

Seen from the facial, the preparationwould look like this.

Fig. 5-21

Fig. 5-22

A cross-section of a tooth with a Type IIIlamination in place looks like this.

The path of insertion for a Type III prep-aration is usually not truly inciso-gingival.Instead, it is usually a hinged path. This factis of clinical significance. If the path of inser-tion were to be inciso-gingival, the normalbulge at the gingival third of the facial surfacewould have to be reduced.

Fig. 5-23

Fig. 5-24

Here is an example of a clinical case usinga Type III preparation.

This patient arrived in the office with aworn and discolored plastic laminate. Afterremoving the plastic, the tooth appearedboth shortened and darkened at the incisalthird. The tooth was vital, but the discolora-tion came from an earlier placement of pins.The incisal edge was rounded (Fig. 5-24) anda porcelain laminate was fused in place (Fig.5-25).

Fig. 5-25

As the occlusal view shows, the laminateextended over the incisal edge to end on thelingual enamel.

Fig. 5-26

In cases where the tooth is not alreadyshortened, the dentist should reduce theincisal edge as shown in this clinical case inwhich the patient had fractured the incisaledges of both central incisors.

Fig. 5-27

Fig. 5-28

After adjusting the incisal edges, and afterslightly reducing the proximals near the gin-giva, an impression was sent to John Morri-son of Mid Kent Dental Laboratories (Sev-enoaks, Kent, England).

Fig. 5-29

The processed laminates were then re-turned and fused into place.

One concern with the Type III preparation is the amount ofunsupported porcelain at the incisal edge. It is too early in thedevelopment of the porcelain laminate technique to be certain,but it is currently believed that the limit will be the same as forporcelain fused to metal restorations. In the latter procedure, itis undesirable to have the porcelain extend more than 2 mmincisally past the metal framework. Extension well beyond thislength is believed to invite fracture through the incisal porcelain.Such is probably also the case with porcelain laminate veneers. Itis with cases such as this one that we shall perhaps learn thelimitations of the porcelain laminate.

In this case the patient had fractured theircentral incisor.

Fig. 5-30

A porcelain laminate was fused into placeto create a restoration with excellent esthet-ics. The restoration was conservative, andthe appearance was beautiful. It is only withtime that we will begin to know whether thisrestoration and others like it are overextend-ing the technique (Figs. 5-31, 5-32).

Fig. 5-31

Fig. 5-32

78 COLOR ATLAS OF PORCELAIN LAMINATE \F\ RS

Fig. 5-33

Type IV. Over the Incisal Edge with aLingual Ledge. The Type IV preparation isvery similar to the Type III preparation.They both extend past the incisal edge of thetooth and wrap around to the lingual surface.In fact, from the facial, the two preparationtypes are identical.

Fig. 5-34

The difference is found in the gingivalmargin of the lingual porcelain. In the TypeIII preparation, the laminate ends in a knifeedge. In the Type IV preparation, the gingi-val porcelain on the lingual is a deep chamferor even a shoulder. Theoretically this in-creased bulk is designed to provide increasedstrength in situations where the fusingstrengths are expected to be below optimal.

Fig. 5-35

A clinical example of such a use is shownhere.

This patient exhibited severe wear of theplastic facings present on the pontics of thisetched metal bridge. The teeth were pre-pared by lowering the incisal edge of thepontics being repaired, reducing the bulk ofthe plastic on the facial

. . . and cutting a ledge on the lingual.Fig. 5-37

True fusing was not possible here, butstandard cementing was used to adhere thefacings in place.

Fig. 5-38

Fig. 5-39

Type V. Maximal Preparation. The TypeV preparation consists of a general reductionof the entire labial surface of the tooth to beveneered. In addition, it is usual with a TypeV preparation to include some sort of cham-fer finish line at the gingival. This prepara-tion type is used whenever maximum bulk ofporcelain is desired for masking out underly-ing discolorations, or whenever any increasein labial bulk must be minimized. Suchwould be the case when treating an individ-ual tooth that is correctly aligned with theneighboring teeth, as seen in these views, orwhenever the teeth to be laminated arealready in slight labio-version (Figs. 5-39,5-40).

Fig. 5-40

One area of concern with a Type V preparation is the gingivalchamfer. It must be recognized that in the adult any such finishline will routinely end in dentin. This brings with it severaldisadvantages, perhaps the most obvious one being patientdiscomfort during preparation. Clearly, drilling into dentin mustbe considered a less comfortable procedure than drilling intoenamel.

Fig. 5-41

The second disadvantage is the potential for difficulties ofadhesion onto the dentin. It is generally considered unwise toplace composite resin directly onto exposed dentin for fear ofcreating hypersensitivity. Because of the precision fit of thelaminate, there is insufficient space between the tooth andlaminate to allow for a layer of a liner such as glass ionomercement covered by a layer of composite. Experience to date hasshown that these chamfers are so shallow as to permit placementof composite directly on the dentin without untoward effects.

Another advantage of the Type V preparation is that it makesthe least change in the labio-lingual thickness of the tooth, andthe increased thickness of porcelain is believed to lead to agreater control of the final color of the tooth.

Since the porcelain laminate technique is primarily an estheticone, color is almost always of absolute vital importance. Unfor-tunately, however, control of the color of porcelain laminates alsocan be one of the greatest esthetic challenge the dentist may face.

Color control is never a problem in cases where the veneer isto match the underlying tooth color. In those cases it is merelynecessary to use both a porcelain and composite of a shade thatmatches the tooth. Difficulty arises when the finished product isto be a very different shade than the underlying tooth becausethe porcelain laminate must be translucent. If the laminate wereto be made fully opaque, it would have a lifeless appearancecompared to natural teeth.

In order to have a natural appearance, it isnecessary to have light penetrate at least ashort distance into the porcelain before beingreflected back. This creates the optical illu-sion of depth. In a restoration in whichporcelain is fused to metal, the dentist ac-complishes this by painting a layer ofopaquer over the metal, and then by cover-ing it with a generous layer of translucentbody porcelain. One millimeter of porcelainand opaquer often is used to create thelifelike restorations to which we have becomeaccustomed.

Fig. 5-42

Carrying this approach to the veneers, the ideal situationwould be for the laminate to have a micro-thin layer of fullyopaque material on the intaglio, with the main body beingcomposed of translucent material. At present, due to the thick-ness required by the opaquer, such a fabrication technique hasnot been developed.

Fig. 5-43

Perhaps the most challenging clinical situ-ation of them all is when two or more teeth ofextremely different coloration need to bematched to the surrounding dentition. This isnot a very difficult problem with porcelainfused to metal, but with porcelain laminatesit calls to the fore all of the dentist's artisticand technical skills. In such cases, a knowl-edge of the esthetic qualities of the materialsand the requirement of a trained eye areimportant. In addition, this situation has ledto an intense search for methods to preciselycontrol the shade of the finished veneer. Thissearch has resulted in the development of theClass VI preparation.

Fig. 5-44

By 1984 it was clear that some preparationtypes give the technician greater control,while others put more control in the hands ofthe dentist. This figure shows a wax "set-up"made using denture teeth. One central inci-sor has been removed and used to make amold. Two models of the incisor were madefrom this mold out of dark brown plastic.Specks of red and other colors, as well as astainless steel wire, were also mixed into theplastic. The result was two "teeth" identicalin shape to the original denture tooth, butdramatically darker and discolored.

Then each of the two models (dies) wereprepared. One of the dies was given a minoramount of preparation. It was a "Type V"(maximal) preparation, but only about .4 mmof die was removed. The second die wasgiven a much more aggressive Type V prep-aration, in some places cutting nearly .9 mminto the die.

Fig. 5-45

These two dies were then placed into the wax-up, and animpression was taken of each of them. Cosmetic Concept DentalLaboratories (Calgary, Alberta, Canada) created a porcelainveneer for each die. The laboratory technique and materials wereidentical for both veneers. The resulting veneers differed bynearly 100 percent in maximum thickness. The first veneer withthe shallow preparation had a maximum thickness of .5 mm, andthe deep preparation resulted in a veneer with a maximumthickness of 1.0 mm.

Side by side on the workbench, the ve-neers look nearly identical. Only by usingcalipers is it possible to realize that theveneer on the left is twice as thick as the oneon the right.

Fig. 5-46

Fig. 5-4 7

When lit from behind, however, the dif-ference in thickness becomes apparent. Un-der these circumstances, the thicker veneerappears slightly darker than the thinner ve-neer because the former transmits slightlyless light than the latter. It is easy to see thatthe thicker veneer will do a better job ofhiding underlying discolorations than thethinner veneer. Perhaps even more impor-tantly, it is also easy to see that even withsuch a very aggressive preparation, the dif-ference in hiding power will be small .

Placed on the dies without the lutingagent, the veneers still appear identical.With the luting composite, however, a slightdifference becomes discernible. As expected,the thicker veneer (on the left) does a per-ceptibly better job of hiding the underlyingdiscoloration than does the thinner veneer.

Fig. 5-48

In the mouth, the thicker veneer matchesthe surrounding teeth more accurately thanthe thin one does.

Fig. 5-49

CHAPTER 5 TOOTH PREPARATION FOR PORCELAIN LAMINATE VENEERS 8 5

Thus in cases of slight discoloration, a thickveneer can be used to mask the underlyingdiscoloration with little difficulty.

Fig. 5-50

When the porcelain itself is not sufficient to mask the discol-oration, as in our extreme example, the dentist must find someway to deal with the color chairside. In freehand compositeveneers, it is common to neutralize the unwanted color first andthen to add the desired color. This is a very effective way tohandle the situation for freehand veneers, but it is completelyinappropriate with the porcelain veneers.

Color can be "neutralized" by adding its complementary color(see chapter 6). For example, we can take a yellow sample andneutralize the yellow by adding violet. When we do this, theyellow becomes greyish.

What does this mean clinically? It means that we haveremoved the offending yellow but have also changed the value(brightness) of the sample substantially in the process. This is animportant concept. Since brightness is more important to the eyethan color when shade matching, we have taken a bad situationand probably made it worse.

When "freehanding" veneers this is not a problem, but it is aserious complication for porcelain laminates. If this were to be afreehand composite veneer, the "neutralizing layer" of pigmentwould then be covered with a layer which would bring up thevalue to what we desired. Unfortunately, when using the porce-lain laminates. the amount of space for the composite luting agentis minimal, and does not not allow for multiple layers ofpigmentation within the luting agent. It also is important to notethat the thickness of the luting composite for preparation typesI-IV remains the same whether the tooth has been conservativelyor aggressively prepared.

The result is that the most predictable results occur whenusing the luting composite either to modify the underlyingdiscoloration slightly or to simply mask over it. One commonmethod used to mask minor discolorations is to coat the inside ofthe veneer with an opaquer composed of titanium dioxide andresin. This layer is painted on, but not cured prior to insertion,because if it were to have puddled in any of the internal angles ofthe veneer the hardened resin would prevent accurate place-ment. In addition hardening this layer before placing the veneeron the tooth often creates a thickened layer of luting composite,which in turn causes the veneer to be too physically prominent.Sometimes this effect is augmented with a layer of opaquer onthe tooth as well.

Fig. 5-51

To demonstrate the degree of opaqueingthat can be expected with this technique, wepainted both the thick and thin veneer anddie with opaquer, and then luted the veneersas usual. As can be seen in these illustrations,when the technique of painting the veneerand die with opaquer is used, the results areimproved. These figures also show the differ-ences that can be expected between the thickand thin veneer. Once again the thick veneer(Fig. 5-51) shows a greater masking effectthan the thinner veneer (Fig. 5-52).

Fig. 5-52

Even though these photographs show that the masking effectof the painted opaquer is slight, it is clear that in cases where themasking effect of the porcelain is not enough, the addition of alayer of opaquer can help.

A still greater blocking effect can be achieved by adding theopaquer directly to the luting composite. The most commonopaquers consist of either of pure titanium dioxide or a mixtureof titanium dioxide with a transparent filler. These materialsshould be used carefully. The addition of a slight amount oftitanium dioxide slightly increases the value of the luting com-posite, while making it more opaque. Any more than a tinyamount, however, causes the composite to become a densewhite. Sometimes this density is desirable, and other times it isnot. Clinical judgment on a case-by-case basis is important.

In the case shown here, there was a dis-tinct improvement in value when a densewhite composite was used. Unfortunately,the desired hue was not even approached bythis method. It is interesting to note, how-ever, that in this case the thin veneer dis-played the greater amount of change whencompared to the thick veneer.

Fig. 5-53

This occurred because the too white un-dercoating shows more easily through thethin veneer than the thick one.

Fig. 5-54

Fig. 5-55

It would seem logical that a thick veneerwill always mask stains better than a thin one,but this is not always true. When using veryopaque luting agents a thin veneer (on theleft) can be superior at masking.

Type VI. Double Preparation. This finding suggests themethod for maximum control of the final color by the dentist.Since the dentist has control of the density and shade of theluting agent, the thicker the layer of composite, the greater theamount of control he will have. As a direct result of thisobservation, in May 1987 McLaughlin published the sixth prep-aration category (Type VI),' called the "double preparation".

The double preparation is used when the dentist desiresmaximum change between the natural color of the tooth and thefinal shade. This preparation consists of two stages. In the firststage the dentist prepares the tooth using a Type I (minimal)preparation and then takes an impression. When the veneersarrive, and after they are tried on for shape and size, the areas ofthe tooth requiring maximum change in color are reprepared intoa Type V (maximal). preparation. This creates a gap between theveneer and tooth sufficient enough to place a totally opaquemasking layer of composite. Although the composite used shouldbe totally opaque, it must also be the final shade desired for therestoration (see chapter 7)

In our example, we took the die which hadreceived the more conservative preparationand deepened the preparation to equal thatof the other die. An opaque composite wasmixed, and the veneer was fused into placeusing standard technique. This photographshows that even severely discolored teethcan be masked using the double preparationand opaque composite.

Fig. 5-56

PREPARATION VS. NON-PREPARATION

The decision of whether or not to prepare a tooth prior to thefabrication of a porcelain veneer is dependent on three factors;the condition of the tooth, the reason it is to be laminated, andthe predisposition of the dentist.

In certain cases, such as a very darkly stained tooth, or a toothin labial version, the choices are limited. In order to create athick enough veneer to mask dark stains, some enamel may haveto be removed. Similarly, a tooth may be buccally positioned, afactor that certainly precludes the addition of an extra halfmillimeter to its labio-lingual dimension. A tooth may be rotatedto an extent that a mesio- or disto-proximal line angle protrudesfrom the arch. This protrusion should be eliminated prior tobeginning any cosmetic procedures. These are situations thatare, to a great extent, beyond the control of the operator.

Some practitioners do not feel comfortable adding anything toa tooth that has not been reduced. While this can apply to fullcrowns and bridges, in the area of Cosmetic Dentistry thisattitude must not be taken for granted.

It should always be an objective of Cosmetic Dentistry toenhance the patient's appearance as much as possible, whilekeeping tooth modification minimal. Whenever possible, Cos-metic Dental procedures should be planned so they are essen-tially reversible. If the patient tires of his new appearance, or ifa superior technique becomes available, it should ideally bepossible to return the tooth to its original condition. Obviously,if any preparation has been performed, this cannot be accom-plished.

Minimal or no preparation also is immediately desirable fromthe patient's point of view. It is easier to understand andsubsequently to submit one's self to a constructive procedurerather than a destructive one. When little or no reduction is

done, there also is no need for anesthesia. It is usual practice forthe entire minimal modification type of procedure, including thefusing process, to be done without the use of an injection. This iscertainly a desirable point that the dentist would want to bring tothe attention of the patient during the case presentation. The lackof a need for anesthetics also can be a boon in the treatment of theelderly, who may have complicating medical conditions, as wellas the young, who may be difficult to anesthetize.

In addition, anything more than minor preparation bringswith it further complications.

TEMPORIZATION

One of the greatest problems facing the dentist who doesundertake maximal preparation is that of temporization. Becauseso little (less than 1 mm) has been removed from the tooth, andbecause care has been taken not to leave any undercut areas,there is literally nothing for a temporary to hold on to withoutetching.

In all such cases the problems are the same. The dentist isfaced with the dilemma of choosing the strength with which thetemporary will adhere to the tooth. Too little strength, and thetemporary pops off the first time the patient sneezes. Too muchstrength, and the dentist literally has to grind the veneer offwhile attempting to leave the underlying topography of the toothunaltered -a tricky proposition at best. If too much is ground, itcould result in complications when seating the laminate, whiletoo little would guarantee that the laminate would not properlyfit. Additionally, if the original preparation went down to thedentin, anesthesia would probably be needed to grind away thetemporary. On top of all this, the temporaries often represent acompromise in esthetics.

The adhesion of the temporary has been addressed in severalways. Sometimes excess composite can be extruded between thecontacts of the adjoining teeth, and this can serve as a weak,albeit unhygeinic, attachment. Sometimes the temporaries are"spot welded" to the tooth by etching only one or two spots onthe labial surface of the tooth each about a millimeter indiameter. Neither system is very good, but they both work to afashion. Unfortunately, while either of these methods can holdthe temporary in place for a short time, they will sometimesdebond by themselves, causing embarrassment for the patient.

At the same time that the dentist is attempting to make atemporary that will not be inadvertently removed, but will easilypart from the tooth on command, still another consideration mustbe made. A serious problem on occasion has been the percolationthat occurs at the unetched margins of the temporary veneers.Although the time involved is too short for any major dentaldecay to begin, the presence of oral fluids in close proximity tofreshly prepared enamel and dentin can be uncomfortable.

CHAPTER 5 TOOTH PREPARATION FOR PORCELAIN LAMINATE VENEERS

That having been said, the authors have attempted a numberof methods of temporization: Preformed Mastique Tm acrylicveneers (L.D. Caulk Co., Milford, Delaware) have been tried.The esthetics of this method (considering the very short temporalrequirement of about one or two weeks) are relatively good.

Another method is to use somewhat flowing composite resinand "freehand" a quick veneer. This method is also serviceable.Still another method is to take a pre-preparation alginate impres-sion and use it as a mold to make either self-cure composite orplastic veneers, which are then adhered by either the "spotwelding" or "interproximal excess" methods.

As can be readily appreciated, temporary veneers take muchtime to fabricate and even so engender more problems than anyother aspect of the entire procedure.

Of course, the patient is better served when the preparation isrestricted as much as possible, or even eliminated altogether. Inthe past, dentists have measured their effectiveness by theamount of tooth structure they have replaced; in the future, wemust evaluate our success by the amount of tooth structure wecan preserve.

REFERENCES

1. McLaughlin, G.: Controlling color in the porcelain laminate.Compend Cont Educ. 8(5):362-371, 1987.

Prior to any enamel reduction, it should be decided whetherlocal anesthetic is required. It has been the authors' experiencethat most preparations can be comfortably accomplished withoutthe need for a local anesthetic.

For all preparation types, the operator must constantly keepthe desired final result in mind throughout the preparationphase. He also must keep in mind the space available in the archfor the veneers and the intended path of insertion.

Fig. 6-2

Instrumentation for the Type I-MinimalPreparation

The Type I (minimal) preparation oftenrequires a slight reduction of the facio-proximal region near the gingiva in order toprovide a path of insertion that is free fromundercuts. For this purpose a torpedoshaped instrument, such as the Robot 835Fdiamond, will do the job nicely. If a slightremoval of surface irregularities (i.e. ridges)is required, then the same tip can be used togently smooth the labial surface.

If only enamel polishing is needed, then a polishing cup, suchas the Quasite cup, will remove the plaque or other foreignmaterial on the surfaces of the teeth. A prophylaxis paste orlaboratory pumice may be utilized in conjunction with the cup.As a final step for the Type I preparation, the contact pointsbetween the veneered tooth and its neighbors should be checkedto verify that an interproximal mylar strip can be placed duringthe fusing process. If the contacts are too tight, they should berelieved using a polishing strip.

Instrumentation for the Type II-Incisal Preparation

As described in the previous chapter, it is often desirable tocreate along the incisal edge a thickness of porcelain greater thanthat afforded by the Type I preparation. Such a situation calls fora Type II preparation. Because of the great similarity betweenthe Type I and Type II preparations, the technique for the TypeII preparation is exactly the same as for the Type I, except thata reduction of the facial enamel on the incisal I to 2 millimetersof the tooth is necessary. This reduction is accomplished by usinga torpedo shaped diamond bur such as the Robot 835F. Thus theentire Type I and II preparations can be accomplished with onlya single diamond.

CHAPTER 6 CLINICAL PROCEDURE FOR PORCELAIN LAMINATE VENEERS 95

Instrumentation for Types III and IV-"Over the Incisal Edge" and "Over theIncisal Edge With a Ledge" Preparations

The dentist may decide to shoe the incisaledge completely, as in the Type III or TypeIV Preparations. In such cases a coarserdiamond, such as the Robot 835, is used onthe incisal edge, since more tooth structuremust be removed than in the delicate Type Iand II preparations. On the lingual surface,many dentists find a football shaped diamondsuch, as the Robot 883F, is handy for creatinga nice knife-edged margin for the Type IIIpreparation.

Fig. 6-3

If a lingual ledge is desired (Type IV), then the usual instru-ment used on the lingual surface is a cylindrical or torpedoshaped diamond, such as the Robot 835F.

After adjusting the incisal edge, the more refined adjustmentsto the proximal areas along the gingival can be made using a finerdiamond, such as the Robot 835F. In addition, the areas cut bythe coarse diamond should be smoothed using the finer diamondas a finishing step. In fact, when any coarse diamonds are used forpreparation, it is useful to finish the tooth with a fine diamondprior to taking the impression, since any striations of the toothsurface can complicate the laboratory procedure.

Instrumentation for the Type V-MaximalPreparation

If a Type V Preparation is indicated, then acoarse diamond such as the Robot 835 shouldbe utilized, taking care to leave as muchenamel intact as possible. This is especiallyimportant along the borders of the prepara-tion.Leaving intact enamel serves two pur-poses: first the tooth will be less sensitivefollowing the procedure; and second, bond-ing agents currently exhibit significantlyhigher bond strength to enamel than to den-tin.

Fig. 6-4

96 COLOR ATLAS OF I ;

Since it is highly desirable to refrain from penetrating theenamel during preparation, many dentists prefer to use a depth-limiting or depth-marking diamond such as the Lasco DC4(Lasco Diamond Products, Chatsworth, Ca.). It should be re-membered, however, that the proper depth of enamel reductionis not consistent over the full surface of the tooth. Thinnerenamel in the gingival regions, for instance, dictates that theenamel reduction be limited or even curtailed in this region.Still, many dentists find the depth-marking diamond to behelpful in visualizing the proper depth of enamel reduction.

Fig. 6-5

In all cases, the enamel reduction shouldnot be carried past the contact points me-sially and distally, since this could place themargins in a less accessible area for cleansingand might create undercuts (considering thelabial approach of the veneer placement). Inaddition, the loss, of proximal contact wouldallow for tooth movement during the fabrica-tion of the veneer. Where inciso-lingual re-duction of the enamel is desired, a footballshaped diamond, such as the Robot 883F,will remove the excess tooth structure.

IMPRESSION TAKING

Following the preparation phase, the ap-propriate impressions need to be taken. Therequired records are an accurate model of theprepared teeth and their neighbors, acounter model, and a bite registration.

The impression materials of choice are thepolyvinylsiloxanes, such as Mirror 3, (KerrManufacturing Company, Romulus, Michi-gan) and Express (3M, St Paul, Minnesota) orthe polyethylethers, such as Impregum(Espe-Premier, Norristown, Pa.).

If taken separately, the bite registration

material should be a putty or silicone type.

When these materials are used, the labora-

tory has the option of cutting away part of theregistration material to see the interdentalrelationships better. Wax wafers may be

used, but they do not have as reliable arigidity as the first two substances.

Fig. 6-7

There are two slightly differing techniques

of taking impressions for veneers. One is the

standard full tray system that dentists arefamiliar with from use in crown and bridge

procedures. An anterior sectional impression

is usually more than adequate. Only those

teeth to be veneered and the adjacent two

teeth on either side are of any consequence

unless the contralateral tooth is being used

for reference.

Fig. 6-8

The common method is to place the putty

in the tray . . . ,

98 COLOR ATLAS OF PORCELAIN LAM I\ \l'!: \ I \(:I H

Fig. 6-10

and to inject the tip-mixed light body directlyonto the teeth, along the cervical margin andinterproximally.

Fig. 6-11

The putty filled tray is then compressedover the arch.

Fig. 6-12

The resulting impression will show themargins, the labial surfaces, and the inter-dental areas clearly, so the laboratory tech-nician will have a clean model upon which tofabricate the veneers. The pressure of theputty will force a small flash of light-bodymaterial subgingivally, demonstrating to thetechnician both the space available and thenature of the free gingiva.

Another, and perhaps easier, technique forimpressions is the use of the Anterior TripleTray (Espe-Premier, Norristown, Pennsylva-nia). This is a single-step procedure thatutilizes putty on both sides of the tray gauzeand light body on the teeth to be veneered.The light body is spread on the appropriateteeth, and the patient is asked to bite into theputtied tray.

Fig. 6-13

The final impression, the opponent, andthe bite are all ready within seven minutes.

Fig. 6-14

If retraction cords are used, the subgingival areas will be morevisible, but the laboratory will have no idea of the location of thegingival margin, and will have to guess the cervical finish line forthe veneer (unless a cervical finish line has been incorporated inthe design). Perhaps as a carry-over from full coverage types ofpreparations, some dentists insist on using retraction cords intaking impressions for porcelain veneers. While the authors ofthis text do not subscribe to this idea, the choice remains a matterof personal preference.

Once the impressions and occlusal records have been taken,the shade is established, the laboratory prescription written (seechapter 7), and everything is sent to a laboratory. When theveneers are returned, the internal aspect of the veneers willalready have been etched at the laboratory. The dentist needonly clean the teeth being veneered before the placementprocedures can begin.

Fig. 6-15

PLACEMENT

The veneers are tried on to establish theirfit, length, and mesio-distal dimension. Allthe veneers to be fused must be placedsimultaneously in order to accurately observetheir interrelationships and esthetic impact.At this time, the dentist is primarily con-cerned with verifying that all areas of toothneeding coverage will be adequately coveredby the veneer and that all veneers will beseated properly. At this try-in, the dentistshould place the veneers on the teeth in theorder that he will be fusing them. This isdone to discover if any veneer interferes withthe seating of its neighbor.

Fig. 6-16

Should any adjustments be necessary atthis stage, they may be carefully undertakenwith a high-speed diamond, such as theHybrid T&F 0931 or the 0935 in a concentrichandpiece. This step must be very gentlyaccomplished because the unsupported por-celain is very fragile and can break even withmedium finger pressure. Generally, littleadjustment is needed at this stage if thelaboratory has taken care in the production ofthe veneers.

Fig. 6-17

ATTACHMENT OF THE VENEERS

Many manufacturers make kits for fusingporcelain veneers to teeth. Each has itsproponents and detractors. In the end, thechoice of kits is a personal decision. Theauthors have chosen to demonstrate the Por-celite Kit (Kerr Manufacturing Company,Romulus, Michigan) because of its complete-ness (all the items needed for this phase ofporcelain veneers are included) and becauseits composite shades are well suited to mostcases without further alteration. It is logicallypackaged, allowing the operator to visualizethe sequence from left to right. There areseparate modules for etching, fusing, andcolor modification.

CHAPTER 6 CLINICAL PROCEDURE FOR PORCELAIN LAMINATE VENEERS

After the initial contouring is complete,the etched concave surfaces of the veneersare treated with an orthophosphoric etchliquid.

Fig. 6-18

This is essentially a degreasing step toremove any materials that may have col-lected on the veneer's laboratory-etched fus-ing surface.

Fig. 6-19

After one minute, the etchant is washed offwith water.

Fig. 6-20

Fig. 6-21

A second application of liquid etchant isplaced, and this is not washed off.

Fig. 6-22

Then the Kerr Porcelain Primer (the si-lane) is applied. It can be seen displacing thelayer of etchant on the veneer.

Fig. 6-23

Alter one minute, the veneer is thoroughlyrinsed . . .

and then gently air-dried.Fig. 6-24

The teeth that are to be veneered are thencleaned again with pumice . . .

Fig. 6-25

and rinsed.Fig. 6-26

The teeth are then isolated from each other by mylar strips(and wedges if necessary). The. lips are retracted from theoperating area by means of cotton rolls or lip retractors. Thefollowing fusing procedure is then followed, completing onetooth at a time.

Fig. 6-27

The teeth are etched with an orthophos-phoric acid etchant ...

Fig. 6-28

very thoroughly rinsed (Fig. 6-28), andgently air dried. The properly etched toothsurface should exhibit a frosty appearance.

The Kerr Bondlite is mixed for about tenseconds in the special dish provided.

Fig. 6-29

Approximately one drop each of the acti-vator and resin per veneer is required. TheBondlite is then applied in a very thin layerto both the etched tooth surface . . .

Fig. 6-30

and the bonding surface of the veneer. Agentle stream of air should be used to spreadthe Bondlite into as thin a layer as possible.Do not light cure at this time.

Fig. 6-31

Fig. 6-32

If needed, a Porcelite Shade Modifier isselected. These are pastel-like colors thatprovide a moderate amount of shade modifi-cation. It is provided in the six followingshades: untinted, universal, yellow, yellow-brown, gray-brown, and opaquer.

Fig. 6-33

Esthetic requirements often dictate thatno one particular shade modifier be used onits own; rather, a gradient of color is created,more dark-yellow toward the gingival,brighter in the main body of the tooth, andmore blue-gray translucent at the incisal.Shading requires clinical judgment and theability to readily visualize both needs andresults. This, of course, improves with prac-tice. There is no need to blend the shades atthis point. Even if the shade modifiers areplaced on the veneer in separate spots, thepressure of placing the veneer onto the toothsurface tends to blend the various modifiersinto an esthetically pleasing gradient.

Fig. 6-34

The veneer is then filled with the propershade of composite cement, being careful toavoid entrapping any air bubbles. Place theveneer against the tooth and apply gentlepressure until the veneer is seated. Theveneer should not be exposed to strong lightuntil the position and appearance has beenverified.

The veneer is now examined for position,color, success in stain masking, and its rela-tionship to the other teeth or previouslyplaced veneers. For the first veneer, thepatient should be consulted at the time ofcolor modification. If the resulting appear-ance is the desired one, the veneer is againchecked for position on the tooth with lightfinger pressure, and then the cure is begun.

Fig. 6-35

If the color is incorrect, the veneer is carefully taken off thetooth. Both the luting-composite and the shade modifiers can beremoved from the veneer and the tooth by a brush or cotton swabdipped in Bondlite. Then different color modifiers are selected,and the process is repeated. In particularly difficult cases, thisstep may have to be done a number of times. There is no specificnumber of trials; when the color is correct, then the dentist cancontinue.

If further, or more distinctive color characterization is re-quired, then this may be accomplished with the Command ShadeModification Kit (or any other similar kit) as described in chapter7.

Light curing is a prerequisite modality when dealing withporcelain veneers. Self cure materials, even if available, couldnot give the type of temporal latitude that is required in theplacement of laminates. Although most curing lights may be usedin this procedure, the ideal unit would incorporate a very strongoutput (because the light must pass through a half millimeter ofporcelain before it reaches the composite), a low heat output (forpatient and operator comfort during this often long treatment),and, if possible, a readily interchangeable wide-diameter andcurved wands.

Fig. 6-36

Since different units provide lights of dif-fering intensities, we will describe the appro-priate times using one particular light: theEFOS 35 (Engineered Fiber Optic Systems,Mississauga, Ontario).

Fig. 6-37

When the operator is ready to cure theveneer, he begins by shining the light on theincisal edge for a period of five seconds usingthe curved wand tip. Generally, while this isbeing done, it is a good idea to keep a veryslight finger (or instrument) pressure on thelabial surface of the veneer to prevent it fromaccidentally lifting away at the gingival.

Fig. 6-38

The excess composite all around the ve-neer (proximal, gingival, and lingual) will stillbe in a plastic stage at this time, and shouldbe gently removed with an explorer or ascaler. The emphasis is on "gently" here,without nicking the periodontal tissues. It isclearly desirable to avoid any gingival bleed-ing at this point in the placement procedure.The wetness of bleeding can weaken or de-stroy any subsequent fusing as well as causediscoloration and formation of voids.

When the flash elimination is completed,the labial surface of the veneer should becured with the wide-diameter wand for 40seconds. Following this, the veneer is curedfrom the inciso-lingual direction for 20 sec-onds with the curved wand.

Fig. 6-39

The interproximal flash is again removed,and the fit of the adjacent veneers are re-checked at this time. If there is any change inthe seating of the unfused veneers from theprevious try-in (before the current veneerwas fused), the offending area must be iden-tified and removed. This flash removal can bedone with a high-speed diamond such as aHybrid T&F 0937 or with metal polishingstrips such as G-C Metal Strips (G-C Inter-national Corporation, Scottsdale, Arizona). Ifthe seating of the remaining veneers is notverified each time a veneer has been placed,there might be a discrepancy that will inter-fere with the fusing location of the adjacentveneer. This error could become cumulativeand result in a situation where the last veneermay be distally displaced by up to one milli-meter.

Fig. 6-40

The order of veneer placement is a matter of personal prefer-ence, but most practitioners seem to prefer placing one of thecentral incisor veneers first, followed by the other central incisor.This is then followed by a lateral incisor, then the other lateralincisor, and so on. Once the general color scheme has beenestablished, all the teeth being veneered will be shaded accord-ing to that pattern. The experienced practitioner will often shadethe lateral incisors slightly different from the centrals (usually abit darker), and the cuspids slightly different yet again (usuallysomewhat yellower). Any pattern of veneer placement is accept-able, but it is usually- easier for the dentist to keep track of thespecific variations in shading and highlighting if he does thecorresponding teeth on either side one after the other.

POLISHING

After the veneers are all fused into place, the polishing processcan be initiated. Some operators prefer to polish each veneer andits margins before the next veneer is placed; but the authors feelthat this tends to increase the possibility of gingival bleeding and,therefore, may make the remainder of the veneers much moredifficult to place.

Using a thin, pointed, high-speed instru-ment such as the 0937 (Fig. 6-41), all theremaining interproximal composite excessmust be removed from both labial and lingualaspects. As much as possible, it is importantto blend the porcelain margins to the toothsurfaces and thereby eliminate any potentialtraps for bacteria or food. If there are anymarginal voids, composite can be added atthis stage to fill them.

All lingual flash is removed with a fine,football-shaped diamond or stone, such asthe 883F. The veneer must always be con-toured to the tooth lingually and checked forunwanted occlusal interferences. The 883F isused for selective removal of lingual porce-lain, composite, or opposing tooth structure,until the desired occlusal harmony isachieved.

Fig. 6-42

Very often the porcelain and the lutingcomposite form a cervical ledge either at orslightly gingival to the free gingival margin.This ledge at the cervical margin of theveneer must be removed to ensure a com-pletely smooth transition between the toothand the veneer. If possible, the finish lineshould be supragingival. l This reduction ofthe porcelain margin is done with the 0931

Fig. 6-43

. . . or the 0935 and the contouring is carriedinterproximally as far as the areas that werefinished with the 0937.

Fig. 6-44

Fig. 6-45

When all the excess composite has beenremoved and all the margins are smooth, afinishing stone, such as a Dura White Point

Fig. 6-46

. . . or Dura White Wheel is utilized to createa continuous transition that is not detectableby passing an explorer from the tooth to theveneer. The White Wheel RE1 0229 is suit-able in open, accessible areas, while theWhite Point FL2 0223 is especially suited forinterproximal and gingival marginal situa-tions.

Impregnated silicone disks, such as theCeramiste' Discs, polish the embrasure areasto a high luster. They should be used bothlingually and labially and are often employedto polish the cervical margins. The Ceram-iste' Discs come in three textures: the discwithout yellow lines-0252 is to be usedfirst, . . .

Fig. 6-47

then the disk with the single yellowline - 0255,

Fig. 6-48

. . . and finally the disk with the doubleyellow line-0258, which has the finest grit.

Fig. 6-49

Fig. 6-50

Similarly, the lingual margins, and anylabial parts of the veneers that have beenadjusted, are polished with the impregnatedwheels such as the Ceramiste' Wheels-0253,0256, 0259. The three textures are used inthe same sequence as the disks (Figs. 6-50,6-51, 6-52).

Fig. 6-5 1

Fig. 6-52

The time spent polishing each tooth should

be limited so as not to cause undue heating of

the pulp, and should be done in a wet field if

possible.

If the facial aspect of the porcelain has

been altered, the final lifelike sheen is im-

parted through the use of polishing cups suchas Quasite Cups, 0295. These are used in thesame manner as prophylaxis cups-, ensuring

that all surfaces are buffed.

Fig. 6-53

It is important to go slightly subgingivally

in the cervical areas of the teeth to be certain

that these margins are particularly smooth

and that all the minute remaining particles of

composite or bonding agent are removed

from these particularly irritable locations.

Fig. 6-54

Fig. 6-55

The Quasite Cups may be used wet or inconjunction with a diamond or compositepolishing paste, such as Command UltrafineLuster Paste (Kerr-Sybron, Romulus, Mich-igan). Again, to prevent overheating, thepolish should be restricted to several secondsper tooth (Figs. 6-55, 6-56).

Fig. 6-56

POST-OPERATIVE INSTRUCTIONS

As with all dental procedures, the patient who has receivedporcelain veneers needs to be taught the proper maintenance ofhis new teeth, as well as what to expect from them in the future.To prevent misunderstanding or misinterpretation, the authorssuggest that the post-operative instruction sheet on page 118, oran information sheet similar to it, be given to the patient aftercompletion of the porcelain veneer procedure. The reader isinvited to copy the page included in this text if he so desires.

Of short term concern to the patient will be that his lips mayfeel full for several hours. This results not only from the increasedlabial dimension of the veneers, but also from the fact the the lipshave been packed with cotton rolls or held in an extendedposition by a lip retractor for an extended period of time toensure the dryness of the operating field.

If the incisal lengths of the anterior teeth have been increased,the patient may have temporary difficulty articulating the soundsof D and T. The tongue will acclimate within hours, though, tothe new reality, and this problem will quickly disappear. Thepatient should be warned, however, so he will not assume this isa permanent condition.

The patient should realize that the veneers are there to beenjoyed. While there are some restrictions with the veneers,they are virtually the same restrictions that should be observedwith natural teeth. The new veneers should not be used forchewing on pens, pencils, ice cubes, or chicken bones. Thepatient should avoid trimming his fingernails or cutting nylonfishing lines with his restorations. He should be made tounderstand that the gentler he is with the veneers, the longerthey will last.

Although these rules are self-explanatory, for many patientsthey will involve the changing of habits established over manyyears, and the process may be much more difficult than thedentist realizes.

The patient also should be advised to avoid having fluoride gelplaced on the veneers in subsequent dental recall appointments.The free hydrofluoric acid in the gel can etch the surface of theporcelain, gradually eliminating the highly esthetic glazed sur-face.

As the literature indicates that the silane bond increases instrength for the first 24 hours after fusion, the patient should beadvised not to chew gum or any hard or sticky foods for one day.Beyond that, he can consider the veneers as normal functionalparts of his natural dentition.

In addition to listing what the patient should avoid, there mustbe a very clear indication to the patient that he must not onlymaintain his regular regimen of oral hygiene at home, butperhaps should improve it. Brushing and flossing of the teethmust not be discontinued.

Finally, the patient should be asked to return approximatelyone week post-operatively for a quick check of the cosmeticresults and an evaluation of the gingival response. If anything hasbeen missed during the fusion appointment, the dentist will havean opportunity to correct it at this stage.

REFERENCES

1. Silness, J.: Periodontal conditions in patients treated withdental bridges. 111. The relationship between the location ofthe crown margin and the periodontal condition. J PeriodontRes. 5:225-229, 1970.

POST-OPERATIVE INSTRUCTIONS

Your porcelain veneers have been designed and created for optimal beauty andstrength. Even though they are composed of fine porcelain, they have great strengthdue to their powerful attachment to the underlying tooth structure. Still, there area few points which you should observe to minimize the chance of breakage.

Fig. 7-2

While this created some organization ofthe color perception experience, it was only abeginning. At the time of its discovery, thecolor circle seemed to describe some basiclaw of physics, but it turns out that theorganization of color into a color circle hasmore to do with the physiology of the eye andpsychology of the observer. It does, how-ever, form the basis for several of our presentday workable systems of color.

Fig. 7-3

In 1905 A. Munsell, an artist and artteacher, further modified the color circlefurther, devising a system of color organiza-tion which centered around three uniqueaspects of color: Hue, Chroma, and Value.Using these three aspects, Munsell was ableto construct a three dimensional color wheel.

CHAPTER 7 COLOR AND THE PORCELAIN LAMINATE

The Munsell system is not unique. Numerous other colorwheels are available. Each is of different national origin, withversions from Britain, France, Germany, Argentina, and Swe-den. Naturally enough, each system finds its greatest usage in itscountry of origin.

Unfortunately, while such systems provide a good way todescribe color, they actually do little to teach us how tomanipulate and control color in a clinical situation. In otherwords, rather than the Munsell system being a method which weuse to control color, it merely serves as a relatively precise"language" to verbalize what we are doing. In fact, it is even oflimited value in describing tooth color, since it is primarilyinvolved with surface reflection. It does not make any distinctionbetween one color that is relatively translucent and one that isopaque.

Differences in surface texture also are not addressed by such asystem. All dentists have seen the differing appearance ofporcelain crowns and plastic temporaries of the same color.Subtle differences in appearance can even be discerned betweenvarious brands of porcelain, variations that can transcend thequalities of hue, chroma, and value. Obviously, then, there aredimensions to the appearance of tooth shade beyond that ofmerely color. This situation is not unique to dentistry.

As a method of recreating the appearanceof real objects on canvas, van Eyck in thefifteenth century developed a system ofpainting which he called the "wet" system.With this method, paintings consist of mul-tiple layers. Different details o£ the paintingsare placed in different stratum over the can-vas. The layers of paint toward the outsideare usually increasingly translucent, creatingthe illusion of depth and vitality which wouldbe impossible if only opaque paints wereused. Sometimes as many as 30 layers areused to create maximum effect. This is notthat different from the technique a masterdental technician uses when different shadesof porcelain are employed to imitate thedentinal and enamel layers along with flecksof inlaid color.

Fig. 7-4

Thus in some respects we are not much farther along than theartists of the Renaissance in our ability to control the chromaticappearance of our work. Nonetheless, there are several princi-ples that guide us.Today's dentist must understand that there areseveral completely unique systems for understanding and manip-ulating color, and while each of them provide a workableframework for our understanding, they also may often seem tocontradict the teachings of the other systems.

The Additive System

For instance, many textbooks discuss three primary colors ofred, green, and blue. They teach that all other colors are madeup of combinations of these three unique or "primary" colors.

Fig. i-5

Knowledge of this system (the so called"additive" system of color) has enabled thecreation of such devices as the modern colortelevision. Using only three phosphors, eachbeing of one of the three primary colors, thecolor television is able to produce a seem-ingly unlimited range of shades. One suchtelevision monitor boasts of a palette of16,777,216 colors available on the screen.

Fig. 7-6

In using the additive system, white is thebalanced mixture of all the colors, and blackis the absence of color. Yellow is a balancedmixture of red and green.

CHAPTER 7 COLOR AND THE PORCELAIN LAMINATE 123

The Subtractive System

Since the additive system of color doessuch a laudable job of organizing color, it mayseem that there would be no need for anyother approach. Those involved in art, how-ever, tend to emphasize yet another arrange-ment. In this system, the so called"subtractive" system, the three primary col-ors are red, yellow, and blue.

Fig. 7-7

In the subtractive system, black is theresult of a mixture of the three primaries, andwhite is the absence of color. This system ispopular because it is perhaps the easiest touse when dealing with pigments.

Fig. 7-8

There are other systems as well. Each color system has its ownstrengths and deficiencies. Yet despite the apparent contradic-tions in the various color schemes, each popular system ofanalyzing color is correct within its own framework. Since wework with pigments when we deal with porcelain veneers, theeasiest system for us to use as clinicians is the subtractive system.

The subtractive system is not only theeasiest for us to use, but also the one withwhich we may be most familiar. The subtrac-tive system is the one we have used since wefirst used crayons. We all know that if we mixred and blue, for instance, violet is the result.

Fig. 7-10

This system works the way it does becausethe pigments within the crayons absorb cer-tain parts of the spectrum and reflect others.Thus the pigments are "light traps". Redpigment, for instance, absorbs all parts of thelight spectrum except red.

If pigments displayed perfect efficiency,the mixture of any two primary colors wouldresult in the production of black. If in ourexample one crayon absorbed all the spec-trum except red, and the other one absorbedeverything except blue, there would be noth-ing left over. Normal pigment concentra-tions, however, are notoriously inefficient inthis regard and are almost always thinned outto create a relatively low saturation.Thus ared crayon selectively absorbs certain wave-lengths, and reflects those centering aroundthe 700 nm (red) range.

Because of our familiarity with the rudiments of this system,and because of its easy applicability to the dental situation, all ofour discussions of color throughout this chapter will take placewithin the framework of the subtractive system of color.

In the subtractive system, when the threeprimary colors are arranged in the traditionalcolor wheel, diametrically opposed colors arecalled complementary colors. Yellow and vi-olet, for instance, are complementary colors.The mixture of two highly saturated comple-mentary colors results in the elimination ofcolor and the production of black. Since thepigments we use are poorly saturated andimperfect, the mixtures of our stains usuallyproduce some shade of grey instead of black.

Fig. 7-12

PROBLEMS INHERENT TO MATCHING THESHADES OF TEETH

There is a list of difficulties the dentist must overcome whentrying to make a perfect match of a tooth's color. Not the least ofthese problems is discovering the actual color of the tooth beingmatched. As every dentist knows, this sounds easier in theorythan it is in practice.

The apparent color of a tooth will beaffected by the color of the incident light. Forexample, in full-spectrum light a tooth mightnormally have a reflectance curve such asthat shown here.

If the source of light changes, however,the apparent color can change dramatically.Here is a normal transmission curve of atypical incandescent light bulb.

And here is a normal transmission curve ofa fluorescent light tube.

Shown here are the two different reflec-tance curves our tooth would display underthese two different sources of light. Evenwith a constant source of light, the lightwhich actually reaches the tooth can be af-fected by the colors in the environment at themoment. A dark shade of lipstick, or anintensely colored outfit can easily effect theavailable spectrum for reflection by thetooth.

In addition, there are variations in opera-tor sensitivity. Color blindness is no smallproblem. It is a fact that nearly one in tendentists in the United States suffers fromsome degree of color deficiency in thered/green areas. If other color deficienciesare also included, the percentage of visuallydeficient operators goes up even further. Thechances of a male dentist being color defi-cient is more than ten times that of his femalecounterpart.

12S COLOR .ATLAS OF PORCELAIN LAMI\ ATE V EAEERS

Fortunately, most of these operators are not color "blind" butonly color deficient. Unfortunately, this means that most of themare not even aware of their handicap. In most situations, such adeficiency is of little importance, but in the case of estheticdentistry, even minor weaknesses in color perception can com-promise the intended results.

Obviously, then, it would be to each dentist's advantage to betested for color sensitivity. Even if a minor deficiency is found, asimple solution may be to have another staff member who is notcolor deficient confirm all color choices.

Even when the dentist's natural color sensitivity is found to beoptimal, however, there is still no guarantee he will makeconsistent color judgments. The eye can suffer from a decrease insensitivity from nerve fatigue, the same as any other sensoryorgan. For this reason, it is important to avoid staring at the toothand shade guides when taking a shade. Instead, short glancesshould be employed, with the first impression being consideredthe most accurate.

One other important point should be made here. During thefusing procedure, the area is isolated. If many laminates arebeing fused in place, the isolated teeth will have time to begin todesiccate. After only a few minutes of drying, the appearance ofthe teeth begins to change. The dried tooth becomes markedlywhiter, and its surface more opaque.

Fig. 7-18

To demonstrate this, we took a patientwith perfectly matched anterior teeth andplaced a rubber dam, exposing the maxillaryright central incisor for 20 minutes. Whenthe rubber dam was removed, the differencein appearance was clearly evident.

Obviously, any shade decisions must be made while thenatural teeth have not desiccated. On more than one occasion, alaminate has been placed in the mouth, and although the shadecreated in the laminated tooth was perfect, the neighboring teethhad lightened by the time the procedure was completed. If thisis anticipated, the patient should be warned in advance that thelaminated tooth will appear a bit dark for one day, but that it willmatch when the unlaminated teeth re-hydrate.

METAMERISM

Most evidence points to the fact that theeye is a tristimulus colorimeter. Like thecolor television, which is capable o£ produc-ing thousands of colors from only three basiccolor phosphors, the eye can discern a nearlyinfinite range of color using receptors for onlythree wavelengths. Also like the color televi-sion, these three receptors seem to havetheir greatest sensitivity around the colors ofred, green, and blue. While this design maybe conservative for the number of requiredreceptors for color vision, it does lead di-rectly to the problem of metamerism.

Metamerism is the effect that is achievedwhen two samples of color appear to match inone type of light, but do not match in an-other. Simply put, the eye is incapable ofdistinguishing between certain combinationsof light stimuli. Both spectral curves shownhere are perceived as yellow-green. So underfull-spectrum lighting, the surface which re-flects light centered around 540 nm would beindistinguishable in hue from one which re-flects two loci of reflectances with one cen-tered around 490 nm and the other around650 nm.

When the lighting source changes, how-ever, the perceived color of the objects alsochanges. Sunlight on an average day pro-duces a spectral distribution similar to theillustration here.Contrast this with the curveshown on Figure 7-14 for typical tungstenlight. As can be seen, when our sample isilluminated by a tungsten source, there isvery little light in the 490 nm range availablefor reflection. When that happens, the sam-ples no longer match. The sample repre-sented by curve A appears red-yellow intungsten light, while sample B continues toappear yellow-green.

This example is by no means unique. Anearly infinite number of combinations canbe computed which create metameric pairs.This pair, for instance, demonstrates one ofthe many pairs that would appear to be blueunder full-spectrum light, but which wouldnot match under other light sources. In thiscase, we have a metameric pair because theeye cannot distinguish between a pure bluehue at 475 nm and the combination of 440 nm(reddish blue) and 490 nm (greenish blue).

The pair shown here would be seen asyellow. Unfortunately, metamerism is a com-mon illusion in our field. One factor thatcomplicates this even further is the fact thatour vision is most acute in the yellow colorrange a color range of particular importancein dentistry. In other words, not only are weunable to accurately determine a non-metameric color match, but our eyes havebeen uniquely designed to be most sensitiveto this error in the yellow range.

Fig. 7-23

Still another type of metameric pair can becreated as a result of the fluorescent nature ofteeth. It is well recognized that when naturalteeth are exposed to ultraviolet light theyseem to glow. Figure 7-23 shows a modelunder natural full-spectrum lighting. Thesame teeth are seen in Fig. 7-24, but thistime the source of light is an ultraviolet bulb.

The apparent glow of the teeth is due totheir own natural fluorescence. Early at-tempts to achieve natural looking fluores-cence in porcelain involved the inclusion ofsmall amounts of radium into the porcelainmixtures, but that practice is no longer used.Instead, certain fluorescing rare earths areincorporated into the porcelain.

Tooth fluorescence is not uniform across allshades. Early this century, when severaldentists made a careful study of the fluores-cent properties of teeth, it was noticed thatcertain teeth were more fluorescent thanothers. Usually teeth with the lighter shadeswere the most fluorescent. This led directlyto the development of dental porcelains withvariable fluorescing properties. One suchexample is found in Austenal's MicrobondNatural Ceramic.

Fig. 7-25

This figure shows the various shades ofMicrobond Natural Ceramic under ultravio-let light. The bottom row shows the variousincisal porcelains, the next row up shows themain body porcelains, the next row showsopaquers, and the top row shows the actualshade guide used when taking shades. It isclear that an effort has been made to matchthe degree of fluorescence of the porcelain tothe anticipated natural fluorescence of theteeth.

These findings are of direct importance toporcelain laminates. This figure shows a pa-tient with non-fluorescent porcelain coveringboth maxillary central incisors. The photo-graph was taken in natural light. Clearly, thedentist and laboratory technician have done acreditable job of creating a natural appear-ance, and the match between enamel andporcelain is good.

Fig. 7-26

When this same patient is exposed toincreasing amounts of ultraviolet light, how-ever, the shade match falls apart, and thedistinction between the natural teeth andthose covered by porcelain becomes obvious.You can judge the quality of light in thisphotograph by the skin tones. Obviously thelighting used in this example could easilyoccur both in natural lighting, such as duringa hazy day, or in man-made lighting, such asin a disco, on stage, or in front of a cameraflash.

Fig. 7-27

When under extreme ultraviolet condi-tions, the porcelain covered teeth actuallyseem to turn black.

Fig. 7-28

c( OLOR ATLAS OF PORCELAIN LAMINATE VENEERS

Fig. 7-29

This type of metamerism is easily avoided.When a fluorescent porcelain is used in placeof the non-fluorescent one, the shade matchcan even carry over to situations with intenseultraviolet light. Here we see a model innatural light with porcelain restorations cov-ering the maxillary left central and lateralincisors.

Fig. 7-30

When seen even under extreme concen-trations of ultraviolet light, the shade matchwith the natural teeth continues. Clearlythere is a distinct advantage to creating theporcelain laminate veneers out of a variablefluorescing porcelain. There also can be someadvantage to using a luting agent that dis-plays variable fluorescence.

SOLUTIONS TO THE PROBLEMS OFDETERMINING THE CORRECT SHADE

Some have suggested that the solution to perfect shadematching (i.e. eliminating the creation of a metameric pair) lies inthe use of a full-spectrum light source during shade selection.Unfortunately, this is simply insufficient. As can be seen in Figs.7-19 through 7-22, it is not uncommon to create metameric pairswhich match perfectly in full-spectrum light, but which do notmatch when the lighting changes.

Further, even so called "full-spectrum" lights can vary in theamount of ultraviolet light produced. Once again any singlesource of light used during shade selection will not insure aconsistent color match when ultraviolet light is present in varyingdegrees.

The advantage of a full-spectrum light is that with it the dentistcan be sure that light from all parts of the visible spectrum arepresent during the shade matching. Ideally, this light can serveas a sort of median for all the possible emissive spectra from allthe possible light sources. As such, it may minimize themetameric discrepancies that our patients will experience.

Perhaps a full-spectrum light, combined with a few partialspectrum lights could provide a solution. If a shade matcheswhen under a full-spectrum light, as well as under two or threewidely divergent light spectra including an ultraviolet band, thenat least to a human eye it is highly unlikely that the color matchwill be metameric.

Another possibility is to use a colorimeter. For simplicity inmanufacturing, the colorimeters in the past have mostly been ofa tristimulus variety. This may seem charming at first. After all,if the colorimeter sees exactly the same way that the eye does,then it will surely be able to tell if the color match is metameric.Unfortunately, this is only partly true. A tristimulus colorimeteris only capable of measuring color in the same method used bythe eye. In some light it cannot distinguish between some colorpairs, while in others it will readily detect the difference. Inshort, a tristimulus colorimeter is fooled as often as the eye. Atristimulus colorimeter, used to take at least four readings of ashade using four light sources of varying wavelengths, includingultraviolet, might perhaps eliminate metameric pairs. Unfortu-nately, there is no such unit available today.

136 COLOR ATLAS OF PORCELAIN LAM

Perhaps an easier solution would be a full-spectrum colorim-eter, one which can determine the exact reflective spectra of thetooth being matched. Such a machine is being developed byBertin and Cie. of France under the direction of Dr. FrancoisDuret. It is designed to work in conjunction with a microcom-puter.

Fig. 7-3 1

It consists of a portable sensor for measur-ing the color of teeth, a fiber optic link, aprinted circuit board for an IBM PC, andsoftware.

Fig. 7-32

Shade is taken by placing the sensor tipagainst the surface being measured while thesensor shoots out a bright flash of full-spectrum light. The computer than analyzesthe reflectance and presents a read-out asshown here.

Through the computer software, a shadematch is then obtained for various manufac-turer's porcelains and pigments.

Fig. 7-33

Even this sophisticated equipment, however, does not atpresent analyze the fluorescence of the tooth, nor does itmeasure other qualities, such as the perceived translucence ofthe tooth. It is possible to build a machine capable of thesethings, but for now it is up to the dentist to become sensitive tothese aspects of shading and color matching so as to best createthe intended effect.

FURTHER PROBLEMS IN CREATING PERFECTLYMATCHED SHADES

Even with a perfect understanding of color and its manipula-tion, a few color problems still remain for the dental operator.These are centered primarily around the physical properties ofthe materials. Unfortunately, there are shade variations betweendifferent batches of the same porcelain, and the porcelain fromwhich the laminates are made is usually not even the sameporcelain used for the shade guide. Usually the shade guides usea high fusing porcelain, while the veneers are made from amedium fusing porcelain. In addition, there can be variations inshade between two copies of the same shade guide.

On top of this, changes are sometimes made in the shadeguide, so that a given shade number one year, may be differentthan the same shade number in another year.' Even then, theshades the porcelain manufacturers present do not cover the fullrange needed to perfectly mimic the shade of teeth, oftenexhibiting deficiencies in the red-orange range. 2

The problems are not confined to the porcelain, however,since it is common to have slight variations in shade betweenvarious batches of the same composite. Age also can change theshade of a single batch. Therefore, the shade numbers ofcomposite resin must serve only as a guide to the shade of thecomposite contained within the tube.

Then, too, the shade of the composite coming from the tube isnot the same shade it will be after it is cured. Thus if a porcelainlaminate is placed on a tooth with the composite luting agent inplace, and even if the shade match is absolutely perfect, itprobably will not match exactly when it is cured. The followingfigure shows eight brands of luting composite disks that havebeen fully cured.

On each disk a small amount of the originalcomposite has been placed, but in the un-cured state. As you can see, the shade changewhich occurs from curing is different frombrand to brand not only in magnitude, butalso in direction.

Fig. 7-34

The result is that the dentist needs to learn the color charac-teristics of each material being used. Since the shade of thelaminate fused into place will change during the curing process,the dentist must develop a feel for the direction and degree ofchange so this change can be anticipated in the shade selection ofthe luting agent.

CLINICAL TECHNIQUE FOR SHADE MATCHING

With all these problems, it may seem that taking an accurateshade is a virtual impossibility. Actually, the procedure is quitesimple. The dentist merely needs to be aware of the potential

CHAPTER 7 COLOR AND THE PORCELAIN LAMINATE 13 9

problems and to try to minimize their effect. Since the lightsource is one of the major potential problems, the dentist shouldtry to take shades in a room free from wall coverings anddecorations highly saturated with color. If the patient is wearingbright colors, they should be offset by using a relatively neutralcolored apron. Perhaps the best choice would be a pale blueapron, since this color has been shown to be most restful to theoperator's cones. Obviously, the patient's lipstick should beremoved as well.

During shade matching, it is best to utilizeseveral light sources to minimize the chancesof metameric pairs. At least one of thesesources should be "balanced" full-spectrumlighting such as the Esthelite Shade Match-ing Unit (Efos, Inc., Mississauga, Ontario)( Figs. 7-35, 7-36).

Fig. 7-35

Fig. 7-36

In addition, just as the incorporation of varying light sourcescan improve the final match, so can multiple viewers. Thedentist, the assistant, and the patient should all collaborate on afinal shade evaluation. Dentists must remember to remove alltinted glasses before matching colors. It also is important to notethat having looked into the composite curing light, the orangeprotective glasses, or shields, will disrupt a dentist's colorperception for quite a few minutes.

Remember, of course, that teeth rarely consist of a singleshade throughout. The commercially available guides are merelythat, guides to assist in the evaluation and description of a tooth'stotal color. Teeth should be observed on the basis of layers ofcolor with pockets (or islands) of characterization.

The minimum evaluation should describe at least three layers(gingival, body, and incisal), each with its particular shade andspecific demarcation lines. It should be noted at this time that indoing six anterior veneers, it is unlikely that each tooth will beshaded identically; the dentist should therefore take an extramoment to describe the individual shade patterns for each toothseparately though contralateral teeth may be mirror images.

CONTROLLING COLOR DURING ENAMELFUSION OF THE PORCELAIN LAMINATE

Once the porcelain laminate is returned from the laboratory,there are two basic methods for controlling the final color of therestored tooth. One technique utilizes translucent pigmentmixtures and involves a two-step system that neutralizes un-wanted shades and then adds the wanted shades. The secondtechnique is more direct and involves masking unwanted shadeswith opaque pigments of the desired shade. Both techniqueshave their place. The neutralization/addition technique is prop-erly used when the shade of the porcelain laminate itself is notexactly correct, while the "cover-up" technique is more effectivein adjusting the shade of an overly dark tooth.

Neutralization / Addition

When adjusting the shade of a tooth, knowledge of the natureof complementary colors can be extremely useful. If, for instance,the porcelain laminate appears a bit too bright at try-in, all weneed to do is to paint the inside of the veneer with a bit of itscomplementary color.' This will have the net effect of slightlydarkening the veneer.

This same technique is used for the selective removal of colors.If a veneer is too yellow, for instance, we can remove the yellowportion of its shade by adding violet.

The one thing complementary color pigments cannot do ismake the shade brighter. The addition of a complementary coloralways decreases the total brightness of the veneer.

We also can augment the existing colors in the veneer byadding pigment on the inside of the veneer. This process is oftenreferred to as characterization. The ability to add this color underthe translucent shell of the veneer is one of the characteristics ofthe porcelain laminate that allows us to create restorations withtremendous vitality. Unlike conventional porcelain crowns,which have to be stained on the surface, any chairside stainingwill increase, rather than decrease, the lifelike appearance of therestoration.

In the following example, we have taken aset of normal shaded laminates and appliedadditional pigment in the intaglio.

Fig. 7-37

The pigment in this case is normal labora-tory stains that have be mixed with a silaneand allowed to dry. The silanated pigment isthen picked up by a brush which has beenbarely moistened with unfilled light-curedresin. If the brush is too moist, the pigmenttends to flow uncontrollably on the laminate.More commonly, premixed characterizingstains such as Porcelite Shade Modifiers( Kerr, Romulus, Michigan), or Durafill ColorVS (Kulzer, Irvine, California), are used.

Fig. 7-38

In this example, an extreme amount ofpigment has been placed into the intaglio ofthese veneers in order to show the degree ofvariation that is possible using this character-ization technique.

This view shows the external appearance ofthe laminates after this characterization.

Fig. 7-40

Fig. 7-41

While such a drastic change in appearanceis not usually the object of our characteriza-tion efforts, this illustration dramaticallyshows the inherent power in this coloringtechnique.

Along a more practical line, let us showyou the amount of staining which normalcharacterization involves. Here is a normallooking laminate placed on a tooth. Now letus begin to characterize it.

Fig. 7-42

If the dentist wanted to give the tooth amore youthful look, he could accomplishedthis by creating an illusion of greater incisaltranslucency. This is done by adding a thinband of grey along the incisal edge.

Fig. 7-43

This thin band of grey is then seen throughthe laminate as a shadowy translucent effect.

Fig. 7-44

In contrast, a look of increased age couldbe created through a slight increase in colorat the gingival margin. This is usually ayellow or, preferably, orange band.

Fig. 7-45

Fig. 7-46

If the facial aspect of the laminate appearstoo flat, it is possible to accent the variationsin the thickness of the laminate by addingeither grey or orange stripes.

Fig. 7-47

Grey would be used if the dentist merelywanted to increase the perception of thesurface contour without giving an appearanceof increased age. If the desired effect was tosimultaneously age the tooth, then orange orbrown should be used.

If the dentist wants an increased appear-ance of separation between the teeth, grey ororange should be applied to the lateral as-pects of the veneer. Similarly, areas thatmock decalcifications, stains, cracks, andother effects can be readily created throughthis method.

Fig. 7-48

The "Cover-up" Technique

At times, the porcelain laminate is exactly the correct shade,and yet when it is placed on the tooth with a luting agent, theunderlying color of the tooth shows through. This could becorrected with an intensely opaque laminate. The trouble withthis approach, however, is that the final restoration will lack theappearance of vibrancy and vitality of enamel. A much bettermethod is to use a translucent laminate and to cover the toothshade with opaque composite.

In chapter 5 we have described an experiment that was used todetermine the most effective method of handling this situation.In the experiment, the Type VI (double preparation) techniquewas employed to mask a tooth whose entire shade was vastly outof range of the desired result. A modification of this techniquecan be used for smaller areas that are darkened or discolored.

If a tooth is basically the correct shade, with a small butextremely dark or discolored area, two distinct methods are oftenemployed to control the final result. Both techniques use thedouble preparation technique.

In one method, the tooth is prepared normally in whateverpreparation type the dentist feels is appropriate. The impressionsare then taken and a laminate prepared. At the time of fusing, thestained area of the tooth is then further reduced, and an opaqueluting agent is used to fuse the veneer.

When this procedure is followed, the luting agent should beboth opaque, and the desired ultimate shade for the tooth. Oftenthis will mean modifying the basic set of luting composites byadding shade modifiers and opaquers. Several products havebeen specifically formulated for such an occasion. Kerr PorceliteShade Modification Kit and Kulzer Durafill Color VS ShadeModifiers are examples of two such products which work wellwith this technique.

Alternatively, the tooth could be prepared as usual, and beforethe impression is taken the discolored area could be slightlyfurther reduced. The discolored area could then be bonded overwith an opaque mixture of lightly filled resin to bring thediscolored area up to the value of the surrounding tooth. Animpression can then be taken, and the procedure can continue.

An important thing to remember here is that it is not necessaryto make the opaqued area exactly the shade of the rest of thetooth. It is more important to make it of approximately equalvalue because the entire facial surface will be covered withporcelain, modifying and blending everything underneath. Sincethe eye is more sensitive to value than hue or chroma, differencesin value will be most easily seen in the finished case.

Since the eye cannot see color in dim light, it is easy toclinically separate the quality of value from that of hue andchroma. This can be accomplished by squinting the eyes untilcolor perception is lost. At that point, any spots on the toothexhibiting a large difference in value from the neighboring areascan be easily discerned.

REFERENCES

1. Miller. L.: Organizing color in dentistry. DADA (SpecialIssue):26E-40E, 1987.

2. Sproull, R.C.: Color matching in dentistry. Practical applica-tions of the organization of color. J Prosth Dent 29(5):556-566,1973.

3. McLaughlin, G.: Controlling color in the porcelain laminate.Compend Cont Educ. 8(5):362-371, 1987.

The teeth should be as close to the idealarch position as possible. None of the ante-rior teeth should appear malposed at thisstage. The two sides, on either side of themidline, should correspond within narrowlimits of tolerance.

Fig. 8-2

Fig. 8-3

The margins of the restorations must beinvisible, not just from a front view, but alsofrom the sides. No segments of the underly-ing tooth should be visible, and unlike thisfigure, there should not be any compositefusing material in view.

If there has been an effort made to rejuvenate the patient'ssmile, the plane of occlusion should reflect this; rather than areduced flat plane, it should be a slightly convex indicator ofyouth.

Most importantly, the major concerns of the patient, whetherthey be diastemas, tooth shape, or tooth shade, must have beenovercome and visually eliminated.

TACTILE STANDARDS

Our concerns with the marginal adaptation of porcelain ve-neers are similar to those with any restorative procedure. Themost important difference with respect to most other types ofrestorations is that any defects can usually be quickly and easilycorrected.

CHAPTER 8 CLINICAL EVALUATION 149

All the margins, whether located inter-proximally, gingivally, or inciso-lingually,must be flush and sealed. There can be noexplorer catches anywhere. Any shoulders orledges must be eliminated and polished to anacceptable emergence angle and confluentemergence profile. Even the slightest incon-fluity in the marginal areas will allow foodand bacteria to build up and result in caries,periodontal destruction, or both.

Fig. 8-4

The least visible, and hence the easiest to miss, is the lingualmargin, but this is also the location of the greatest patientsensitivity. If there exists the slightest irregularity, or a minisculegap in the bonding composite, the patient's tongue will find itand constantly return to it, causing irritation. Therefore, after thedentist has evaluated the lingual margins to his own satisfaction,he should ask the patient to make sure the restorations arecomfortable to the tongue.

During placement or polishing, flecks of composite materialmay have lodged themselves subgingivally. These tiny pieces cangreatly irritate the periodontium and within days begin to creategingival destruction. Most dentists who have done compositerestorations are familiar with this type of problem. The solutionis to check subgingivally with an explorer for any bonded or loosechips of excess composite and eliminate them immediately.

Some composite, furthermore, may havebecome attached to the labial aspect of theveneers. Often composite is found by tactileand not visual means, as its color tends toblend in with that of the veneer. Simplypassing a scaler over the porcelain surfaceswill identify the location and extent of thesecomposite excesses. The scaler may be usedto flick the composite off. Utilizing a sharpscaler is preferable to repolishing the area, asthe latter method may damage the laboratoryfired glaze of the porcelain.

Fig. 8-6

The veneered teeth should be cleansableinterproximally with dental floss. Any catchon the floss should be eliminated with fin-ishing strips. There should be functionalocclusal harmony with all existing teeth. Aspreviously mentioned, there is no contrain-dication to locating contact points on porce-lain, but it stands to reason that the operatorwill not wish to have porcelain prematurities.Its presence can be evaluated by the use ofarticulating paper.

If the veneers do contact the lower anteri-ors during protrusive movements, it is pref-erable that this be an even, multi-tooth rela-tionship.

It is predictable that a sole high contact point will cause theeventual fracture of either the laminate or the natural tooth. Thelocation of prematurities also should be identified in lateralexcursive movements, even the most extreme ones, and elimi-nated.

The choice of structure removal for occlusal harmony is at thediscretion of the operator. Each case will be different and shouldbe judged on its own merits. As a general rule, it is preferable toremove the excess from the restoration, except when thisinterferes with the esthetics. In practice, the dentist oftenremoves a small amount from both the restoration and the naturalopponent.

PHOTOGRAPHIC ANALYSIS

Over the last few years, Cosmetic Dentistry has taken greatstrides forward. The esthetic awareness of both patients anddentists has been heightened. In the past, dentists often com-plained that no patient could appreciate the artistry of his skills.Today, the patient can not only see the cosmetic changes inducedby the dentist, but also demands very high standards.

As appearance has become more important, the photographicrecording and evaluation of dental procedures is coming to beregarded as part of the practitioner's normal armamentarium.

It is becoming absolutely necessary to have "before" and"after" records of the dental appearance for legal purposes. Apatient who expresses his dissatisfaction by the means of a lawsuithas the upper hand unless the dentist can demonstrate clearlythat an esthetic improvement was made. Two factors can con-tribute to a patient's lack of appreciation. First, he may forget justhow bad he looked before treatment. Without reminders of theoriginal state of the teeth, he may feel that the dentist's fees areunjustified. Patients are notorious for becoming accustomed to

CHAPTER 8 CLINICAL EVALUATION

better esthetics. Second, cosmetic treatment often involvescompromise. The patient who was expecting to look like a moviestar and ends up only greatly improved may resent this perceivedfailure on the dentist's part. Should litigation ensue, the dentist'sonly means of protection is the photographic record.

Close-up photography (macro-photography) is also essential inself-evaluation. Just as many dentists use loupes to improve theirvision in the micro-environment that is modern dentistry, so theclose-up slide projected onto a wall screen affords the magnifi-cation that will reveal the smallest of mistakes. By examining hisown work, each dentist can pinpoint his weaknesses in prepara-tion or finishing, and thereby attempt to eliminate them. In thismanner, the success (or failure) of shade matching, characteriza-tion, and the creation of illusion are highlighted.

Slides vs. Prints

Both slides and prints can provide a pho-tographic record. However, because of theirspecific limitations, each has a definite use indentistry.

Fig. 8-7

Print film has more grain than slide film, and as a result, printsare always less sharp than slides. Well exposed slides offer morebrilliance, contrast, and color saturation than can be expectedfrom photographic prints.

Slide film has a lower tolerance for varying colors of light, andis thus able to reproduce colors more faithfully. During theprinting process, colors may be partially lost or unintentionallyintroduced; with slides this cannot happen.

Slides can easily be blown up on a screen for presentation atlectures or for self evaluation. Due to the extremely fine grain ofslidefilms like Kodachrome 64, even large magnifications arepossible without distortion.

Slide film also is less expensive and easier to store than printfilm. Obviously, the current medium of choice for the photo-graphic storage of dental images is that of color slides.

Standardization

The objective of "before" and "after" records is to demonstratea changed condition. Thus it is necessary to have some standardswhereby the manner of recording does not influence the ob-served outcome; the conditions under which photographs aretaken have to be similar. Film, camera, and lighting shouldalways be the same for comparative images. A single dentist willusually use the same camera and flash unit for an extendedperiod. He must be sure to use the same film as well.

The developers of photographic film realize that photographsare taken under wide variations of lighting conditions. They havetherefore created different types of film for varying circum-stances. There is, for instance, film created for use with tungstenlighting which compensates for the uneven spectrum of colorgiven off by tungsten bulbs. When this film is used in full-spectrum lighting, the color rendition no longer seems true.

Fig. 8-8

The authors consider Kodachrome 64 thebest standard for dental film. Manufacturedunder very stringent guidelines throughoutthe world, it is developed only by Kodakunder rigorous temperature and chemicalcontrols. Kodachrome 64 also can be used tocompare work that is both geographically andtemporally separated, thus providing a reli-able and standardized comparative evalua-tion of cosmetic and esthetic dental proce-dures (Figs. 8-8, 8-9).

Fig. 8-9

If a dentist wished to "cheat" on his slides,in order to embellish the esthetic effects ofhis work, he would photograph the "before"with Kodachrome 64, showing all the yellow-/brown/red staining of the teeth. Followingtreatment (or no treatment at all), he wouldphotograph the teeth with Ektachrome 64 forthe "after", highlighting the blue and whitetones. The difference would be remarkable.The "after" teeth would appear brighter andwhiter. The improvement would be due onlyto the red filtering effect of the Ektachrome,not any dental amelioration (Figs. 8-10,8-11).

Fig. 8-10

Fig. 8-11

Camera and Lens

There are numerous camera manufacturers and each of themproduce many different camera systems. The most ubiquitoustype of system is the 35mm\ format, a logical choice for a standardformat because of its extensive availability of bodies and suitablelenses.

There are several types of camera bodies, but the best ones forour purposes here fall into the "single lens reflex" (SLR) cate-gory. This mean that the camera has been made in such a waythat when the user looks through the viewfinder, he is lookingthrough the actual camera lens and sees the exact image that willbe projected on the film. In addition, the ideal camera bodywould have an automatic exposure feature with "through-the-lens" (TTL) metering, which is coupled to the flash unit. The

flash-coupled TTL metering effectively becomes a governorsystem that reads the amount of light reaching the film from thesubject and then terminates the flash output as soon as the filmhas been adequately exposed. This innovation has made dentalphotography much less of a mystery to most dentists, since thefilm exposure is fully automated.

The lens should be a good quality 100mm macro-zoom. The"macro" means close-up, and the "zoom" indicates that there aredifferent levels of magnification available. Automatic camerashave correspondingly coupled automatic lenses; an automaticbody with a non-automatic lens works the same way as a totallynon-automatic system.

Fig. 8-12

Typical of this type of camera is the PentaxDental System, although it is only one ofmany fine systems on the market today. Thissystem includes the "Super Program" body.It has programmed into the body six different"modes" of operation, including the auto-matic capacity for interacting with the lens aswell as a flash unit.

The lens shown here is the Pentax Dental Macro A100mmF4.0 macro/zoom. The "A" denotes that the lens can be coupledwith the automated camera body. "100mm" is the focal length, ora measure of the ability of the lens to magnify objects. "F4.0"indicates the widest the lens can open to let in light. The term"macro" is used to differentiate between similar focal lengthlenses for telephoto (far away) work and macro (close-up) pho-tography. "Zoom" is a feature that allows the dentist to changethe magnification of the object without losing his focus. In otherwords, once a tooth is clearly sighted, if it takes up too much (ortoo little) of the frame, the dentist can adjust the size of the imagewithout having to refocus.

There is a direct relationship between the size of the " F stop"number and the depth of field focused in the picture. For ourpurposes, we can consider that the higher the number for theF-stop, the more of the image that is in focus. This depth of fieldbecomes most critical in close-up work, so the dentist almostalways wants as high an F-stop as possible. In dental photogra-phy, a wide open lens, such as F4, will show perhaps one toothin focus, and the rest will be blurred. To avoid this situation, ahigher number F-stop, such as F11 or F16, can be used. Thesewill put most or all of the teeth framed in the slide into sharpfocus.

One way of expressing how close up a lens can take a pictureis to cite the ratio of the size of the image on the film to the actualsize of the object. For instance, many macro lenses of 100mm willpermit a maximum image size of 1:2. On the film, the greatestdimension of the tooth will be 1/2 of the actual life size. This isgood for dental demonstration, but not always adequate. ThePentax system includes add-on close-up lenses that clip ontothe tip of the Al00mm lens and allow 1:1 and 2:1 reproductionratios.

The 1:1 is the most commonly used, butthe 2:1 gives excellent close ups of marginsand finish lines.

Fig. 8-13

The color coded hash marks on the top ofthe lens specify to the dentist exactly whichmagnification he is using. This is particularlyhandy when he wishes to create a standardmagnification of a particular subject at differ-ent times.

Fig. 8-14

Fig. 8-15

In normal focusing operations, the photog-rapher sights his object, and then adjusts thelens to fit the distance. In dental macro-photography, it is the magnification that ispreset, and the dentist physically movescloser to, or farther from, the object until heestablishes the correct focus. Though some-times a bit awkward, this procedure is readilylearned and adaptable to each practitioner.

Along with magnification and focusing,framing is a very important element of dentalphotography. Obviously, the dentist wishesto avoid as much extraneous material aspossible. Cotton rolls, retracting fingers, anddrooping lips tend to detract from the clarityand the neatness of an image. Ideally, onlyrelevant subject material should be includedand this should be centered in the photo-graphic frame. In practice, it is hard to isolateintra-oral subjects from adjoining structures.Therefore, we must use certain framing tech-niques to encourage a viewer's eyes to focuson those subjects of interest (Figs. 8-16,8-17).

Fig. 8-16

Fig. 8-17

Fig. 8-18

In general, there tends to be a visualconvergence on the center of an image. Thusthe subject should be as close as possible tothe center of the frame. When the dentistwishes to point out a condition of a singletooth, that tooth should take up most of theframe; this will result not only in an adequatemagnification for demonstration, but alsotend to exclude any irrelevant material thatmight hinder the viewer's attention Figs.8-18, 8-19).

Fig. 8-19

Fig. 8-20

If a comparison is being made of opposingsides of the jaw, however, both sides shouldbe clearly visible, and, preferably, the mid-line of the teeth should occur at the horizon-tal midpoint of the film.

Where the dentist is showing a smile com-prising both upper and lower teeth, then theentire anterior segment (cuspid to cuspid, orbicuspid to bicuspid) must be visible and infocus. The intermaxillary line should be atthe vertical midpoint of the image and paral-lel to the horizontal edges of the film. Avisually tipped plane of occlusion does notcompliment the esthetics. The means of re-traction, whether with fingers or plastic labialexpanders, do not form part of the necessarypicture, and thus should be eliminated.

Fig. 8-21

The "zoom" is especially handy for thisaspect of intra-oral photography; if there istoo much peripheral material, the dentistneeds simply to move in and thus narrow thefield of vision of the camera. When the visualcoverage is inadequate, one can easily"zoom" out to pick up more perspective(Figs. 8-22, 8-23).

Fig. 8-22

Fig. 8-23

Flash Units

Now that we have a means to record an image and thestandards whereby such a slide is comparable, we still have oneproblem: illumination.

The oral cavity, as every dentist knows, is inherently dark. Theonly way to ensure that the resultant images are bright and clearis through the use of flash units.

In regular photography, a single light source flash unit iscommonly used. While the illumination is adequate, certainshadows will appear, depending on the source direction. Shad-ows are often desirable in portraits, but usually not in dentistry.Some manufacturers have added a second light source to theapparatus. When these are properly deployed (at 180 degrees toone another), they can eliminate most of the shadowing, but notall.

Fig. 8-24

The best flash for dental photography isthe ring flash. This apparatus, which is usu-ally placed at the tip of the macro lens, givesoff a truly circular, 360 degree illumination.All the potential shadow areas are eliminatedand a clearer, more objective, image is pro-duced.

At other times, such as in full-face photographs, some shad-owing is desirable in order to eliminate a flat, featureless look.Thus many dental flash units combine a ring flash with a standardflash unit, with a switch to choose which unit is to be used at anygiven time.

Both flash units should be of the thyristor type, so if less thanthe full charge is utilized, the remaining energy can be applied tothe subsequent recycling sequence. This feature provides a muchquicker re-energizing phase and longer lasting batteries.

Both the flash unit and the camera should have compatiblecoupled TTL monitoring systems. Rather than rely on the oldertrial and error method of devising proper illumination, or on theelaborate calculations based upon film speed, lens aperture, andbackground light, coupled with the technique of "bracketing"(taking 3 or more slides of the same situation to ensure that atleast one of them would be correctly exposed), the dentist simplypresses the shutter release, letting the camera microchip readthe light entering the lens. This control will automatically cut offthe flash as soon as enough light has reached the film plane. Asa result, a dentist can expect to achieve close to 100 percentsuccess with his exposures, whereas 50 percent would have beenconsidered an enviable situation not long ago.

Intraoral mirrors

From time to time, one would like tocapture on film a view that is not visibledirectly to the outside observer such as thebuccal and lingual aspects of molars, and thelinguals and incisals of anteriors.

Fig. 8-25

Fig. 8-26

Various sets of intraoral photographic mir-rors are manufactured to assist the dentistfaced with this problem.

Fig. 8-27

With practice, the practitioner can becomeadept at utilizing these to capture interest-ing, but not readily visible, conditions.

Instant Dental Photography

Not all dentists are inclined to become involved with 35mmphotography, and for this group of practitioners, an instantsystem might be suitable for legal protection. The quality of theprints of an instant camera and film are not as diagnostic or asdetailed as 35mm prints, but because they can be ready in oneminute, they can be an invaluable part of the dental photographicprocess.

The role of the instant photograph in Cosmetic Dentistry ismore geared to internal marketing and patient education than topersonal or peer evaluation, or presentation and publication.These prints are easily made in the dental chair prior to andimmediately after cosmetic treatment. They are then often givento the patient. In the aftermath of a positive esthetic dental

procedure, the patient may show his friends the change andunderscore the description with "before" and "after" photos. Themarketing value of this type of photographic testimonial canhardly be overestimated.

For the dentist, taking instant photographs is much easier thanpulling the appropriate slides, having them printed, and thenforwarding them to the patients. Besides, by the time thiscumbersome procedure is completed, the patient will be accus-tomed to his improved appearance and less likely to show thepictures to his friends.

Unfortunately, the instant photography field has historicallybeen more in tune with family snapshots than with dentalclose-ups. Recently, however, a number of different productssuitable for dentistry have come on the market.

Now there are several complete dentalunits available. One that gives consistentlylifelike results is the Polaroid CU 5 (PolaroidCorporation, Cambridge, Massachusetts).

Fig. 8-28

The CU 5 consists of a camera body, a 75mm lens/shutter, anelectronic ring flash (with a power pack that recycles in about 5seconds), and magnification multipliers. The regular CU 5 bodyachieves a print size:tooth size ratio of 1:1. With the addition ofa magnification multiplier, the ratio becomes 2:1; that is, theapparent size of the teeth on the print is two times their actualsize.

The use of the CU 5 is very straightforward. The appropriateplastic anterior extension is placed against the patient's chin, thecamera is centered, and the photo taken. Both the exposure andthe focusing are predetermined, thereby eliminating any guess-work. The flash functions automatically, but the output can bemodified if necessary. Auxiliary staff can be readily trained to usethis system.

The only difficulty lies in the process of framing. The operatordoes not see the image that he is photographing (as in SLRcameras) and thus has to guess the angulation and left-rightorientation of the unit. With practice, this uncertainty is mini-mized. In any case, since the print is ready within one minute,the dentist can easily retake an exposure that he does notconsider adequate.

These prints also can be used to enhance laboratory prescrip-tions. When appropriate, by giving the technician a visualinterpretation of the the pre-operative condition, the dentist canimprove his communications.

Fig. 8-29

ELECTRONIC IMAGING

Recently, yet another "high tech" instru-ment has entered the field of cosmetic den-tistry. Known as an imaging computer, it canbe used to help plan and communicate pro-jected cosmetic changes. The basic unit con-sists of a video camera and a digitizing padconnected to a desktop computer. Often theunit also comes with a printer or an instantcamera.

The unit was designed to be used as a planning and commu-nication tool. In the normal mode of operation, a still picture ofthe patient is taken using the video camera and the image is sentto the color monitor. Once on the screen, the image can bemanipulated in many ways. Spaces between teeth can be filled,teeth can be lengthened or shortened; tooth shade can bechanged; teeth added or removed. In short, any esthetic changesthe dentist or patient can imagine can be shown on the screen.The images can then be printed on paper or even saved on a diskfor later recall.

The changes are made using a digitizer,which is a sort of electronic sketchpad. Itlooks like a thick plastic clipboard and isconnected to the computer by a wire. In itssimplest function the dentist "sketches" onthe pad using an "electronic pen", whichlooks like a pen with a nylon tip at the writingend and a wire coming out of the top.Wherever the "electronic pen" touches thedigitizer pad, a corresponding area of themonitor screen is drawn over. Thus the"pen" acts as a paintbrush painting the videoscreen.

Fig. 3-30

Colors can be chosen from a virtually unlimited supply. Acommon configuration allows over 16,000 different shades to beused, although if the dentist prefers, the choices of color can becondensed into those of any given standard shade guide. Thesecolors can be painted over the image in opaque or translucentlayers.

The machine is much more than a merepaintpad. While it is capable of painting overthe image on the screen with different typesof "brushes", ranging from opaque solid to a"spray paint can" of translucent water color,the program also allows much more sophisti-cated things to be done with the image. Forinstance, portions of the image can be mod-ified to widen teeth in order to fill in gaps.Individual teeth can be rotated on thescreen, or "orthodontically" moved. Multipleimages can even be overlaid, allowing thedentist to put the teeth of a celebrity, forinstance, into the mouth of his patient.

Fig. 8-31

Fig. 8-32

He can also superimpose x-rays over apicture of the patient.

Fig. 8-33

Here is an example of a sophisticatedapplication of the equipment using thePreView system (InstruMed, Carpintaria,Calif.). In this example, we are going to showone of the ways that the computer can closeup a patient's diastema. First, a "before" pic-ture is taken of the patient's teeth.

Fig. 8-34

Using one of the computer's built in func-tions called "taper polygon", a polygon shapeis superimposed on the screen around thenarrow central incisor.

Using the sketchpad, the polygon is movedto exactly outline the tooth (Figs. 8-35, 8-36).

Fig. 8-35

Fig. 8-36

Then the same method is used to move thepolygon to the shape the dentist desires ...

Fig. 8-37

Fig. 8-38

and the computer automatically changesthe shape of the tooth to the new outline(Figs. 8-38, 8-39).

Fig. 8-39

Fig. 8-40

Naturally, it is easy to zoom in on anyportion of the image to see the fine details,and then zoom back again. Marking facialmidlines, demonstrating the golden propor-tion, bleaching teeth, making darkened fill-ings match the teeth, and virtually any otherfeasible esthetic consideration can be dem-onstrated and visualized on the screen, sopatients can easily appreciate any limitationsof treatment before the work is performed.

In short, using the computer, it is possible to show the patientwhatever changes the dentist has in mind before the procedureis undertaken. Perhaps more importantly, the patient also canclearly communicate the changes that he has in mind. This allowsa more complete communication than ever before. In this waythe patient's expectations can be aligned with procedural reality.

In addition, the cosmetic dentist can include informationduring the consultation regarding the use of make-up to maxi-mize the effect of the teeth. On the screen, various shades ofmake-up can be applied and removed without ever touching thepatient. The patient can, for example, see the apparent toothshade changes that occur by simply changing lipstick. The patientalso can see how other facial distractors can be minimized, andthereby highlight the full beauty of their smile.

Using the same instrument, it also is pos-sible to create side-by-side comparisons ofvarious appearances. The screen can easilybe split into two or more sections. Often thistechnique is used to create before-and-afterpictures of the suggested changes so thepatient can appreciate the full impact of theanticipated changes.

Fig. 8-4 1

With an attached printer, whatever isshown on the screen can be printed into aPolaroid quality print in less than a minute. Italso is possible to combine the actual"before" picture with one that is taken afterthe completed treatment, as shown here.This can then be given to the patient orplaced in the patient's chart as part of hispermanent record.

Fig. 8-42

The major limitation of the video imager comes about becauseit provides only a two-dimensional image. It cannot be used, forinstance, to indicate to the dentist the limits of enamel reduction,or to automatically demonstrate the effect of the rotation of atooth. It also will not give the dentist or patient an appreciationof the thickness of the teeth after the bonding procedures.

Sometimes a given view of the patient will obscure certaindetails that are extremely pertinent to the treatment plan, butthis is not usual. It also is possible to do things on the screen thatare impossible in real life. It would take little effort, for instance,to place a third eye in the middle of the forehead. The operatormust, therefore, be constantly aware of what is possible inreality, making sure he does not overstep those limits.

Still, even with these limitations, it is usually possible toquickly see how good or bad a given treatment plan is withouthaving to go through the mess of working with wax on a plastermodel. In fact, in less time than it takes to take and pour animpression, the entire procedure can be finished with theimaging machine.

This has great implications for time planning, since it essen-tially allows the dentist to accomplish the entire data acquisition,analysis, planning, and consultation, all at the same visitsomething simply impossible by any other means.

Examination of the labial anatomy of thecentral incisor reveals two developmentalgrooves (lines) that run inciso-gingivally andthat divide the tooth into three usually equalsized lobes. These lobes are rarely obvious asindividual entities, though they do form anintegral part of the overall presentation of thetooth. When noticeable, they are most prom-inent at the middle third of the labial surface.

Fig. 9-1

To narrow the appearance of the central incisor, the develop-mental lines should be moved closer together. This decreases theamount of light reflected directly back at the observer (due to thelateral angulation of the tooth structure between the interproxi-mal contact point and the developmental line on the ipsolateralside). In fact, the angulated contour of the proximal surface tendsto deflect light, making this part of the tooth appear darker. Thischange serves to make the tooth appear more narrow sincedarker areas of tooth structure are usually perceived as beingsmaller than their true dimensions.

Fig. 9-2

The developmental lines can also be accen-tuated further toward the gingiva than usualto increase the "long" appearance of thecentral and to add further to the illusionbeing created.

CHAPTER .9 ADVANCED CLINICAL CONSIDERATIONS 173

Where the central should be widened, justthe opposite needs to be done. The develop-mental lines, and hence the lateral promi-nences, should be more widely separated.

Fig. 9-3

The creation of a relatively flat central area will increase theamount of light reflected directly back at the observer and this,in turn, will give the illusion of increased width of the tooth. Theangulated proximal surface will be concomitantly decreased inwidth, and therefore less light will be deflected laterally. Theproximal area will appear brighter and thus larger. To furtherhighlight the mesio-distal bulk of the tooth, the developmentallines should be shortened and restricted to the middle third ofthe labial surface.

The lateral incisor. There is generally a greater acceptance ofsize variability of lateral incisors than central incisors in dentalesthetics. Still, the dentist must on occasion deal with estheticillusions for this tooth. One common situation calling for estheticillusions of the lateral incisors is found where a patient has a verysquare face and large teeth and the lateral incisors are similar tothe central incisors in actual size .

It should be noted that when viewed in sagital section, thelabial aspect of the lateral incisor generally has more curvaturethan that of the central incisor, and there usually is a distinctabsence of developmental lines and prominences. Also, becauseof the roundness of the arch, the lateral incisor is usually notfacing directly forward, but is slightly rotated relative to thecentral incisor.

The seeming width and length of the lateral incisor can beeffected using the same techniques as for the central incisors,with the additional aspect of rotation to simplify the job. Tonarrow the appearance of a lateral incisor, we often wish toincrease the rotation in order to deflect more light away from the

observer. To widen the lateral incisor, the labial surface has to bemade to seem flatter or at right angles to the observer, and thusmore reflective. This illusion can be accomplished by creating aslight decrease in the degree of rotation relative to the centralincisors.

The cuspid and bicuspids. The labial surface of the cuspid issmooth and rounded. Crisp developmental lines, if visible at all,are faint and of little concern or use in the fabrication of veneers.There are, however, three developmental lobes, and the middlelobe is by far the largest. This produces a ridge on the labialsurface (the labial ridge), slightly to the mesial of the verticalmidline of the crown. Distal to the labial ridge, in the cervicalthird of the crown, there is often a concavity. It is the absence ofthis concavity that often gives cuspid veneers a "boxcar" appear-ance.

Fig. 9-4

The cuspid normally presents only its me-sial aspect to the frontal observer, althoughpeople with wide smiles and/or high lip lineswill exhibit the entire surface to view. Thus,while we are primarily concerned with theesthetics of the mesial portion of the cuspid,the distal can contribute to, or detract from,the overall cosmetic value of a restoration.

Fig. 9-5

To narrow the appearance of a cuspid, thelabial ridge should be moved mesially,thereby reducing the mesial proximal area.The decreased reflectivity of the diminishedarea will make the cuspid appear smaller.Since the proximal area is almost completelyperpendicular to the observer's line of vision,it is difficult to change the angulation andthus cause light deflection. Therefore, theentire illusory process depends on the reflec-tive surface area caused by manipulating theposition of the labial ridge.

CHAPTER 9 ADVANCED CLINICAL CONSIDERATIONS 17 5

If there is a need to visually widen thecuspid, the labial ridge is placed more to thedistal. This step increases the area availablefor light reflection on the mesial proximalsurface, thereby magnifying the apparentsize of the cuspid.

Fig. 9-6

The distances that the labial ridge should be moved are veryminimal, as even half of a millimeter in either direction willgreatly influence the perception of the size of the cuspid.

When veneering the bicuspids, a similar technique can beused to increase or decrease the apparent tooth magnitude, butin observance of the lesser frontal visibility of these teeth, evenless displacement of the labial ridge is required.

Illusions in the correction of the labial silhouette. In general,the accepted frontal view of cuspids and bicuspids indicates thatthe labial surfaces of these teeth are parallel. Rotated or mal-posed teeth can destroy this harmony and reduce the estheticvalue of a person's smile. On occasion, inadequate veneerplanning will create cuspids that are well related to the anteriors,but in total disharmony with the remaining posterior teeth. Inextreme cases, this can give the patient an edentulous appear-ance distal to the cuspids.

The laboratory, and ultimately the dentist, must ensure thatthis does not occur. The laboratory will therefore require impres-sions extending at least two teeth beyond the most distal veneer.The dentist should check for parallel silhouettes both on themodel and intraorally.

If a bicuspid is in a lingual position in relation to the arch, it isa relatively easy procedure to ask for a thickened veneer that willrestore the ideal outline. The same tooth in buccal version raisesa different type of problem. It might be easier to restore theother teeth to correspond to the one in slightly incorrect position,or perhaps there could be some labial reduction required of thetooth in question. The decision must be made by the practitionerin each individual case based upon clinical factors and theunderlying concept of maximal tooth conservation.

Illusions in the Inciso-gingival Dimension

The visual length of a tooth is as important to its appearance asits visual width. The apparent length, too, may be manipulatedutilizing light reflection. In this type of illusory procedure, thetechnique for all the anteriors is essentially the same, and thuswill be discussed together.

In order to shorten a tooth, we must reduce the amount ofreflected light that reaches the observer. There are severalmeans of achieving this.

Fig. 9-7 The labial contour of an anterior toothexhibits a certain roundness.

Fig. 9-8

The more accentuated this roundness, themore the gingival and incisal portions of theenamel (or porcelain) are likely to deflectlight rather than reflect it. The less labialsurface available for the direct reflection oflight, the smaller the tooth will appear.Therefore, placing the inciso-labial angle (theline nearest the incisal edge where the cur-vature of the labial surface takes a morepronounced lingual direction) further fromthe incisal edge tends to shorten the appear-ance of the tooth.

CHAPTER 9 ADVANCED CLINICAL CONSIDERATIONS 177

Similarly, locating the gingivo-labial angle (the line nearest thegingival margin where the labial curvature becomes more lin-gual) further from the gingival margin has the same effect asplacing the inciso-labial angle further from the incisal edge.

Teeth occasionally have faint gingivo-labial grooves calledperikymata. These wavy structures have the effect of deflectingincident light in every direction, thereby darkening the gingivalthird of the tooth. This darkening decreases the apparent crownlength and can be used very successfully in creating the short-ening illusion.

The flattening of the incisal edge of an anterior has the effect ofmaking it more square in appearance. This squareness tends tofocus the observer's eyes into the middle of the tooth, alsoimparting an illusion of decreased length.

It is more common, however, to desire that the maxillaryanteriors appear longer. Generally, longer incisors, particularlycentral incisors, are indicators of youth. (It is not to be inferredfrom this that areas in which periodontal surgery has exposedroot surfaces and made the teeth inordinately long are estheti-cally desirable; what is being described here as the ideal is theunworn, posteriorly supported, appearance of the late teens orearly twenties.)

In increasing the apparent length of inci-sors, the light-reflecting area must be maxi-mized. The inciso-labial line should beplaced as close to the incisal edge as possible,and the gingivo-labial line must be located asfar gingivally as the dental conditions allow.This positioning will effectively reduce thelabial curvature, directing more reflectedlight at the observer, and increasing theapparent size of the tooth.

Fig. 9-9

Minimizing or eliminating the perikymata also tends to createthe illusion of greater length. A smoother gingival third istherefore desirable in the lengthening illusion.

Lengthening the middle third of the incisal edge and roundingthe proximo-incisal angles slightly will make the tooth look morerectangular, and therefore will create a longer appearing tooth.

A combination of these illusion-creating mechanisms willresult in a longer or shorter appearing tooth, as the case may be,without actually changing the dimensions.

In most cases, techniques for both mesio-distal and inciso-gingival illusions will be used in concert, in order to achieve anatural, harmonious, and esthetic appearance in the fabricationof porcelain veneers.

DEALING WITH SPACES

Spaces due to misalignment

Fig. 9-10

It is common for the cause of a diastema tobe the misalignment of one or more of theteeth. When that is the case, the patientshould be encouraged to seek an orthodonticsolution. Unfortunately, the patient is oftenalready all too aware of the possibility oforthodontics, but has ruled it out because ofthe nature and length of treatment. If that isthe case, it may be possible to use porcelainlaminates to give the patient "instantorthodontics".

Fig. 9-11

In the case illustrated here, the patient hasa diastema because the maxillary left centralincisor is moved to the distal. To complicatematters, it is rotated over the mesial aspect ofthe upper right lateral incisor. The rightanterior segment is normal.

CHAPTER 9 ADVANCED CLINICAL CONSIDERATIONS 179

After carefully analyzing the case and mea-

suring the sizes, the maxillary left central and

lateral incisors as well as the left cuspidshould be trimmed back in the areas indi-

cated (Figs 9-12, 9-13).

Fig. 9-12

Fig. 9-13

After modifying the teeth, the new appear-

ance from the facial view will look like this.

Fig. 9-14

Fig. 9-15

From the incisal view, it is easy to see thatany overlap of teeth will thus be eliminated.

Fig. 9-16

Laminates should then be fabricated forboth the left central and lateral incisors togive an appearance of proper alignment. Bymaking the laminates thicker toward themesial aspect, it will make the teeth appearas if they are not rotated.

Fig. 9-17

The final appearance from the facial aspectshould look like this.

CHAPTER 9 ADVANCED CLINICAL CONSIDERATIONS

Spaces Due to Size Discrepancies

When the diastema is caused by teethwhich are simply too small for the spaceallotted, the usual solution is to widen theteeth. This is most easily accomplished bycreating laminates that cover the existingteeth as well as the spaces (Figs. 9-18, 9-19).

Fig. 9-18

Fig. 9-19

Fig. 9-20

In this case, five laminates were used tocover the upper incisors and the upper leftcuspid (Figs. 9-20, 9-21).

Fig. 9-22

Fig. 9-21

It is also possible, although far more diffi-cult, to successfully add only a sliver ofporcelain on the proximal surfaces of theteeth adjoining the spaces to fill in the void.Such was the technique used in this case.

The shape and position of the central inci-sors in this case were ideal for such a tech-nique. In addition, there was very littlevariation in the shading of the central incisorsfrom the incisal edge to the gingiva margin. Itwas therefore possible to create these"veneers" for the unprepared central inci-sors. A blend of porcelain with slightlygreater opacity than usual was utilized.

Fig. 9-23

The appearance improved dramatically af-ter the porcelain slivers were fused intoplace.

Fig. 9-24

It should be noted, however, that conditions are seldom soideal. The difficulties created by variations in shading over thesurface of the tooth can be perplexing. There are usually slightvariations in the apparent surface texture between the porcelain,composite luting agent, and tooth. In addition, the finish line ofthe porcelain is clearly visible on the labial surface of the finishedtooth. This can cause an immediate esthetic problem that willbecome increasingly more apparent. All things considered, whilethe apparently conservative nature of this approach is charming,it is usually a second-choice treatment alternative when usingporcelain.

OVERCOMING TETRACYCLINE STAINS

One of the greatest difficulties with tetracycline stained teethis that the tooth structure underlying the finished porcelainveneer is so highly variable in color. Often the operator's effortsat masking the darkly stained portions simply render the lighterareas far too bright and white for a truly esthetic result.

Obviously such a situation calls for a Type VI (double)preparation. In addition, the technique of external bleaching canbe utilized just prior to fusing the veneer. Under normalconditions, the external bleaching of vital teeth is often followedby a complete or partial color relapse, as the oral environmentaffects the cleansed enamel lattices, but such relapses requiresthe access of oral fluids to the bleached prisms. Where this accessis not possible, such as under the fused porcelain veneer, thebleached enamel remains stable.

Fig. 9-25

In the case shown here, the pumicedenamel was partially etched to provide betterpenetration of the bleach. The darker areaswere bleached for up to 5 minutes, thedarker areas being exposed for the longestperiods. Following this extra step, the fusingprocess was resumed from the beginning (theinitial etch). The only other departure fromthe standard veneer technique was the place-ment of an opaquer on the darkest enamelsurfaces during the fusing process.

Fig. 9-26

As can be observed, the resulting veneersnot only are an improvement on the origi-nally severe stains, but also have a verynatural, non-striated appearance, withoutbeing excessively bright or opaque. Theprisms are blocked by resin, and the dangerof color relapse has been eliminated.

RE-ESTABLISHING ANTERIOR OCCLUSALFUNCTION

Many of the early articles on the subject indicated thatporcelain veneers should not be placed in areas of occlusal stress.While it can be certainly stated that there must not be anyprematurities on the veneer, there is no contraindication toallowing full, normal occlusion on either single or multipleveneers. The thin porcelain veneer is a very fragile item.However, when it is fused to a tooth or baked onto a metalcoping, its strength increases dramatically.

One of the less indicated areas for theplacement of porcelain veneers is the loweranterior region. On occasion, however, cir-cumstances dictate that porcelain veneers beused, as shown in this case.

Fig. 9-27

Three porcelain laminates were placed tocover the patient's remaining three mandib-ular incisors. A Type III preparation wasused and the incisal edges of the laminateswere placed in full function.

Fig. 9-28

Fig. 9-29

After 18 months of constant occlusal stressand function, the veneer had neither delam-inated nor fractured. Instead, because of thefact that it was occluding against an unglazedsurface of a porcelain fused to metal fullcrown, the porcelain on both the laminateand the opposing crown showed wear. Theforces at work are evident from the amount ofwear that the mandibular central exhibits.

Fig. 9-30

This is a demonstration of just how strongthe clinical bond between the enamel andthe veneer is, showing that the veneer trulybecomes a physical and functional part of thetooth. Notice the complete lack of crazing orcracking of the porcelain in this extremeclose up view.

TRANSFORMING CUSPIDS TOLATERALS

For a patient congenitally missing laterals,the dentition first presents itself with spacewhere the missing laterals would normallybe. Traditionally, the dentist may take one oftwo orthodontic directions. One is to openenough mesio-distal space between the cen-trals and cuspids so a lateral pontic can beinserted. The other is to close the lateralspace entirely. This latter approach alwaysbrings with it certain esthetic liabilities: thecuspids are almost always larger, darker, andmore conical than lateral incisors. This is thesituation that this patient found herself fol-lowing treatment by an orthodontist.

Fig. 9-31

The only reshaping or preparation under-taken was the removal of the incisal 1/2 mmof the cuspids' points. Veneers were madewith a particular reference to the size of thecentrals. The laboratory was asked to addcertain hypocalcification spots on the lateralsto further aid in the camouflaging of theveneers. Note that these lines, if naturallyformed, will occur at similar levels on thelaterals, but on the centrals,' their positionwill be further gingival (corresponding to theearlier development of the central). The buc-cal aspect of the first bicuspids will recreatethe cuspid illusion, and thus the esthetics ofthe upper anteriors is restored.

Fig. 9-32

Naturally, if the patient is to wear a re-tainer, it must be fabricated to fit over theporcelain veneers on the labial surface .

Fig. 9-33

Two points of caution should be made here. The first is thatwhile it is possible to alter the shape and size of the crown usinglaminates, it is not possible to make the gingival margin of thetooth narrower, nor is it possible to move the gingival margin ina more incisal direction. If the gingival border of the cuspid iscorrect for a cuspid, it will not be correct for a lateral. It will bewider and more apical than that of an ideally placed lateralincisor. Sometimes the patient must be warned in advance thatthe final appearance of the "converted" crown will be imperfectat the gingival margin. Still the potential improvement inappearance is so great that few patients object to this imperfec-tion.

The second point of caution has to do with occlusal stresses. Itis not uncommon with missing lateral incisors for the lowercuspid to nestle just distal to the cusp tip of the maxillary cuspid.In such cases, if a porcelain laminate were used to create theshape of a lateral incisor, the disto-incisal corner of the laminatewould be placed in a position of undue stress where the porcelainwas unsupported by tooth structure.

In such cases, either the maxillary laminate must be madeshorter than the esthetic ideal, or the mandibular cuspid must beshortened.

MOVING THE MIDLINE

It is often necessary to do full orthodontic treatment in orderto realign teeth. This is particularly true in the case of centeringthe midline. If the discrepancy between maxillary and mandib-ular midlines is small, however, it may be aligned cosmetically.

Fig. 9-34

The patient shown here had two 7 year oldMastiques that had chipped and percolated.

The two central incisors required retreat-ment, and it was suggested that the lateralsbe veneered as well. This made it possible toextend the tooth size discrepancy over moreteeth and thus make it less visible.

Fig. 9-35

The maxillary midline was aligned withthat of the lower incisors (as well as that of theface), and the laboratory was asked to fabri-cate veneers with that starting point in mind.

Fig. 9-36

TOOTH/JAW SIZE DISCREPANCY

Often the orthodontist is called upon to correct malocclusionscomplicated by dental size discrepancies. Where the teeth aretoo large, treatments such as serial extraction or interproximalreduction may be undertaken to improve the dental appearance.

A far more difficult situation is that of microdontia. Typicallythe dentition and, in particular, the maxillary anteriors, are toosmall both in terms of facial size and arch width. In the past, theonly method of dealing with this problem has been to apply fullcoverage crowns. The amount of healthy dental structure thathad to be removed was an unfortunate but necessary sacrifice.

The treatment of microdontia by fused porcelain veneers is arecent and very welcome addition to the armamentarium of thedentist. This is a conservative and highly esthetic mode of dealingwith the problem of undersized teeth.

Fig. 9-37

As always, the first step in treating thisproblem is to evaluate of the appropriate sizeof the maxillary anteriors (as described inchapter 4). In the case shown here, themesio-distal space required for the centralsand laterals corresponded to the arch dis-tance available between the mesials of thecuspids.

Fig. 9-38

Next, establish the face-related shape ofthe central incisors. In this case, there was noneed for preparation of the teeth, and thusmaximum conservation was possible.

Fig. 9-39

These three views of the left lateral incisorare from the same case after the two centralincisor veneers had been fused in place.Notice that this tooth required absolutely nopreparation.

This view of the laminate prior to fusingshows the degree of extension required tocreate a tooth of correct size.

Fig. 9-40

This is a view of the tooth immediatelyupon placement of the veneer. Notice thateven though there was no tooth reductionalong the margins, the gingiva is undisturbedwithout any blanching. At the same time,notice the smooth, esthetic gingival marginpresented by the finished case.

Fig. 9-41

It also should be noticed that the shade selected is slightlylighter than the color of the cuspids. This is the most naturalcondition, and every attempt should be made to maintain it.

In the case just depicted, the face size/dental arch relationshipallowed the operator to close all the existing diastemas. For otherpatients this might not be possible. The dentist must thendecide, in consultation with the patient, where the interdentalgaps will occur, and then this information must be clearlycommunicated to the laboratory.

Fig. 9-42

PEG LATERALS

Peg laterals combine the two estheticproblems of undersized and incorrectlyshaped teeth. As such, they are ideal forporcelain lamination. Here is an example ofjust such a problem.

Fig. 9-43

The dramatic improvement in facial harmony which twoporcelain veneers can create is clearly evident in these two fullface photographs (Figs. 9-43, and 9-44).

Fig. 9-44

STAINED RESTORATIONS

Since the earliest days of composite restorations, dentists havefaced the prospects of temporal staining and deterioration. Part ofthe problem lay with the weaknesses inherent in the materialsthat were utilized, but most of the culpability was the patient's.Habits such as smoking, drinking coffee and tea, and poor oralhygiene were (and are) greatly responsible for the estheticfailures of anterior restorations.

It was frustrating to replace these fillings, knowing full wellthat the patient's habits were going to remain, and soon beginundoing these newer restorations. Staining and discoloration(staining is defined as the extrinsic diet and habit induceddarkening of composites while discoloration implies the internalyellowing that occurs due to chemical changes and reactionswithin the composite) have been reduced as better materialshave been developed, but they have not been eliminated.

When the restorations become an esthetic handicap and/or thepatient is unable or unwilling to control his habits, then oftenporcelain bonded veneers are the best solution.

It is important to replace all redecayed and greatly stainedrestorations before the placement of veneers. Failing this, theveneer could be undermined both curiously and cosmetically.The opacity of the veneer and fusing materials can eliminateminor color variations.

Both the phenomena of polymerization shrinkage and thecoefficient of thermal expansion are of sufficient concern whendealing with an attachment to teeth that they have been thesubject of numerous investigations. These investigations dateback to the early search to find methods of attaching materials totooth well enough to avoid leakage. This research has shown thatcomposite bonded to etched porcelain or etched enamel willattach with sufficient strength to avoid later degradation due tothe initial polymerization shrinkage or the subsequent thermalexpansion or shrinkage. When chemical attachment is added tothe physical attachment (the fusing process), the strengthsbecome even more formidable.

In the case of attaching materials to dentin, it is only with themost recent generations of dentin bonding materials that theinitial bond strength of composite to resin exceeded the forcescreated by polymerization shrinkage during cure. Thus, if attach-ment to dentin is required, not all "dentin bonding agents" willbe adequate for the job.

While not always necessary, the authors advocate the use ofthese dentin bonding materials whenever dealing with etchedporcelain over exposed dentin. Further, since porcelain fused toenamel exhibits markedly higher bond strengths than even thebest obtainable to dentin, the prudent dentist will always try toend all porcelain restorations on sound enamel.

Using this technique with porcelain laminates in place ofrepeated composite placements, the operator can now be assuredof color stability for a number of years. The porcelain does notstain or discolor with time. The underlying restoration is notopen to intraoral fluids; thus staining is eliminated as a potentialproblem. Discoloration may continue, but its pace is slow; theveneer's opacity tends to mask small changes.

Some concern has been expressed about having a thickenedlayer of composite beneath the porcelain veneer. These concernscenter around four main areas: compressive strength, tensilestrength, polymerization shrinkage, and coefficient of expansion.

In fact, none of these characteristics need be of great concernwhen dealing with composite resin that has been either bondedor fused to porcelain or enamel. The compressive strength (over34,000 psi) and tensile strength (over 5,000 psi) of compositeresin is sufficient for any proper application of etched porcelain.

Fig. 9-45

In the case depicted here, no unusualsteps needed to be taken. In some cases,however, the degree of enamel destruction isso great that dentin bonding proceduresmust be incorporated. This is simply accom-plished by using GLUMA, Scotchbond 2,glass ionomer cement, or some other similarmaterial under new composite restoration(Figs. 9-45, and 9-46).

Fig. 9-46

First, the patient's name is entered on a form which specifiesthe mold to be used as a guide in the fabrication process. Theguide mold details the general shape and size of the maxillaryanteriors (established in accordance with the Trubyte systemdescribed in chapter 4). This measurement helps the technicianunderstand the general shape the anterior veneers should take.

It has often been remarked that one major problem withexisting laboratory prescriptions has been that too little space isprovided to enter all the required information for a comprehen-sive cosmetic description. If all the details are described in thesmall area usually designated for this purpose, the result issometimes indecipherable.

It is for this reason that on the new form three separate areasare set aside for the various aspects that are to be incorporatedinto the final porcelain product-one each for shade, surfacetexture, and characterization. In this manner, clear instructionsabout the specific features of each tooth can be communicatedwithout the risk of misunderstanding.

The new form also provides a specific reference to the degreeof masking required to reduce or eliminate the existing stains onthe teeth. The form also draws attention to the presence of shortteeth and specifies which ones should be lengthened.

Porcelain veneers can easily correct diastemas, but the patientdoes not always want them eliminated. The form asks the dentistto indicate which spaces will be eliminated and which will be leftopen.

The next area of the prescription questions whether illusionsare necessary, and if so, for which teeth. This is deliberately keptseparate and distinct from the shading section. The final color ofthe veneers must correspond after all the other modificationshave been made. Thus, if there is any illusion creation, this mustnot affect the final cosmetic harmony of the anterior teeth.

The dentist also is required to indicate whether the labialdimension of any particular tooth is to be increased.

Depending on the type of preparation or non-preparation thathas been performed, the technician should be instructed whichteeth are to have incisal edges in porcelain.

There are at least two major theories that apply to the gingivalmargin of a porcelain veneer; some practitioners utilize a flame orknife-edged finish, while others prefer one closer to a butt joint.This, too, can be clearly indicated.

Perhaps the greatest asset of the suggested laboratory prescrip-tion is that it can serve to guide the dentist in the creation of adetailed and complete picture he might not otherwise alwaysprovide. All the information is necessary and important. In fact,this proposed form may be only a starting point, to which eachdentist will add his own specific notations and requests.

CHAPTER 10 THE LABORATORY PRESCRIPTION

Chapter 11 LABORATORYPROCEDURE FORPORCELAIN LAMINATEVENEERS

There are two basic approaches to the laboratory fabrication ofporcelain laminate veneers. The first and most popular of the twomethods utilizes an investment model onto which the porcelainis baked directly. After processing, the investment model iseroded away from the porcelain laminate using a sandblaster.This method was first proposed (and subsequently patented) byMcLaughlin. The second method uses a stone model of the teethagainst which platinum foil is swedged. The porcelain is thenbuilt up on the platinum foil much the same as when making aporcelain jacket. After the final porcelain firing, the platinum foilis removed from the intaglio of the veneer. This method was firstdeveloped and subsequently patented by Greggs.

Each of these two methods has its proponents and detractors.In the end it is a personal decision as to which laboratorytechnique is employed.

Regardless of the laboratory method selected, a detailedimpression including embrasures and sulci is always required.This should be accompanied by an accurate bite registration anddetailed prescription. From this stage on the two methods differmarkedly.

Fig. 11-1

INVESTMENT MODELTECHNIQUE

Andre Dagenais, R.D.T. and Carl L.Lee-Young

If the investment model technique is em-ployed, the technician first fabricates articu-lated, die-stone master models.

Fig. 11-2

The impression is then repoured using asuitable high temperature investment, suchas Whip-Mix VHT Investment (Whip Mix,Lexington, Kentucky), to produce a refrac-tory model. This model need only containthe teeth being veneered and their immedi-ate two neighbors.

Many laboratories believe that if the original impressionmaterial is other than a vinyl polysiloxane or a polyether, it ispreferable to make an index of the master model with a vinylmaterial to produce the refractory model. Problems can occur ifVHT or other similar investment material is used with a water-based impression material, such as alginate or agar hydrocolloid.

Next, the refractory model is degassed intwo steps:

Step 1: Hold the model in a regular burn-out oven at 600 degrees Celsius for 20 min-utes.

Step 2: Then place the model in a porcelainfurnace, and bring the temperature to 990degrees Celsius under full vacuum.

After cooling, the degassed refractorymodel should be soaked in distilled water fortwo to three minutes. Keeping the modelwet allows for easy application of the porce-lain.

Fig. 11-4

The margins may be marked with a ce-ramic pencil (Whip-Mix, Lexington, Ken-tucky). This marking will remain visible afterfiring and will help keep sight of the margin.

Fig. 11-5

A thin layer (0.2mm-0.3mm) of body porcelain is applied to thefull extent of the area to be covered and slightly beyond. This willserve as the base of the veneer. It is sometimes easier to visualizethe thickness of the porcelain if a drop of food coloring has beenadded to the porcelain before applying it to the model. Oncefired, the food coloring burns out leaving only the unadulteratedporcelain behind.

Fig. 11-6

The utilization of a sonic condenser, suchas the CeramoSonic (Shofu Dental Corpora-tion, Menlo Park, California) will give opti-mal results. When doing multiple units, becareful to establish adequate separation be-tween teeth before firing.

Fig. 11-7

Next, dry the model for five minutes infront of the open muffle of the furnace .

Place the model into the oven and fire it to985 degrees Celsius under full vacuum at arise of 45 degrees per minute. At 950 de-grees, release the vacuum and immediatelyremove the model to bench cool.

Once cooled, the base-bake will look like a"slurry" bake on a metal restoration . It willhave a high glaze and usually will exhibitsome cracking due to the porcelain shrink-age. The model should then be resoakedbefore further porcelain application.

Fig. 11-8

Next, the body porcelain is applied to thefull contour desired. The second layer shouldoverlap the first so as to end on the model.Failure to do this will often result in a peelingaway of the porcelain from the model alongthe margins.

Fig. 11-9

Condense well. When making multipleunits, cuts must be made between each toothbefore firing in order to keep the units fromfusing together.

Once again dry the model in front of theopen furnace muffle for five minutes.

Bake the porcelain at the manufacturer's recommended tem-perature at full vacuum. Release the vacuum 35 degrees belowthe peak temperature. Once the peak temperature has beenreached, immediately remove the model and allow it to benchcool.

The model should then be resoaked before adding any furtherporcelain. Correct the body shape with the addition of bodyporcelain where required. Again, any additions to the marginalareas should extend over the present margins and end oninvestment material. Correct the incisal areas with the additionof incisal porcelain as desired.

The final build-up is performed to ready the veneer for firing.The same firing cycle is employed as in the second bake, but atfive degrees lower.

The case' is allowed to bench cool. After thecooling, it is ready for separation and grind-ing.

Fig. 11-12

The finishing is begun with a diamonddisk. The general contours are imparted atthis stage.

Fig. 11-13

The finishing is continued with a greenstone. This step will reduce surface rough-ness and create the rounded features of thefinal product.

Fig. 11-14

Fig. 11-15

Fine diamond burs create the highlights,depressions, and grooves that characterizethe veneer and give it its lifelike appearance.

Fig. 11-16

The case is separated into single die unitsusing a slim separating disk (Figs. 11-16,11-17).

Fig. 11-17

Once separated, further finishing, particu-larly toward the proximal, may be readilyaccomplished.

Fig. 11-18

Small proximal discrepancies and contactsmay be adjusted by adding a mixture of 50percent body porcelain and 50 percent glaze.Natural glazing provides the best results.

Fig. 11-19

Fig. 11-20

The bulk of the refractory material is cut offusing rotary instruments (Figs. 11-20, 11-21,11-22).

Fig. 11-21

Fig. 11-22

The remainder is sandblasted with amicro-blaster using glass beads.

Fig. 11-23

It is important to be especially careful withthin areas on the veneer and with the mar-gins.

Fig. 11-24

The veneer is reseated on the mastermodel in order to verify the fit. The veneershould be checked for mesio-distal, facial,and inciso-gingival contour, as well as foresthetic integrity.

Fig. 11-25

Fig. 11-26

The lingual must also be checked for fit andadaptation. The incisal extension of the ve-neer is also evaluated at this time.

Fig. 11-27

Overextensions are removed with a dia-mond disk or small diamond burs.

Fig. 11-28

The final adjustments are accomplishedwith the fine polishing wheels, such as Ultrawheels and Ultra polishing wheels (ShofuDental Corporation, Menlo Park, California).It is important to support the veneer whiledoing adjustments. Mandrels must bestraight and vibration-free. At this stage, theveneers are quite fragile, and care must beexercised not to fracture them inadvertently.

The finished veneer is checked on themaster model.

Fig. 11-29

The finished veneer is placed on a plasticplate. Using a plastic eye-dropper, a drop of18 percent hydro-fluoric acid or a hydroflu-oric acid mixture is placed on the lingualaspect of the veneer. Depending on theporcelain used as well as the concentration ofthe acid used, the veneer should be allowedto stand approximately two and one halfminutes. Obviously, the technician must ex-ercise great care when handling the acid.

Fig. 11-30

With the help of a plastic instrument, theveneer is pushed into a container of waterand washed thoroughly.

Fig. 11-31

Fig. 11-32

The finished and etched veneer, alongwith the master model, is ready for delivery.

PLATINUM FOIL TECHNIQUE

Thomas Greggs, C.D.T

The laboratory fabrication of porcelain laminates using aplatinum foil technique necessitates the use of individual remov-able dies on a master model made of hard die stone.

The working model is poured using hard die stone leaving aminimum of 3/8 inches of working area between the gingivalmargin and the base. All the dies of teeth to be veneered, and theadjacent teeth should be pin indexed. A base is poured andallowed to completely dry.

Fig. 11-33

The outline of the labial gingival margins ofall teeth to be veneered are indicated with asharp red pencil. Other red lines are drawnfrom the embrasures to the model base onboth the labial and lingual surfaces to directthe sectioning of the base. The sectioninglines should be parallel to the dowel pins.(Film for Figs. 11-33 through 11-67 courtesyPVS System, Cercom International, Ar-monk, N.Y.)

The entire model is dislodged from its pinindexed base by selective tapping on thepinned model.

Fig. 11-34

The incisal edges of the pinned model areplaced on a base of soft white wax to serve asa cushion while the model is sectioned. Themodel is first sectioned in half by cuttingbetween the central incisors from the base upto the embrasure. When the saw bladereaches the embrasure, the saw should beremoved and the two model sections are thencarefully snapped apart. The interproximalsurfaces must not be cut with a saw. Thisprocess is continued for individual dies untilall dies have been separated.

Fig. 11-35

The marginal area of each die is exposedwith a #8 round bur, undercutting the gin-gival margin one quarter of the bur diameter.Proximal margins should be undercut withless depth; approximately 1/16 the bur diam-eter.

Fig. 11-36

Fig. 11-37

Unless a prepared gingival margin exists,the gingival undercuts are placed either atthe red outline, or 0.2mm beyond. A largebud bur should be used to trim the excessstone in order to create a smooth cylindricalshape for easy access to the labio-gingivalworking surface.

Fig. 11-38

All flaws and undercuts are filled withblock-out material to facilitate effective foilremoval. The dies should then be coatedwith surface hardener for increased durabil-ity.

The platinum foil matrix serves as a substructure for theporcelain veneer buildup, as well as a heat-conducting matrixthat brings the porcelain to a uniform maturity during the firingcycle. Platinum foil thickness commonly used for veneeringmeasures 0.00085 to 0.001 inches in thickness. Handling char-acteristics of each manufacturer's platinum foil may vary due todifferences in pliability and rigidity. To assure consistent han-dling characteristics and predictable results, platinum foil specif-ically designed for porcelain veneering procedures is recom-mended (Cercom International, Armonk, N.Y.).

Instruments of the highest quality are ex-tremely important in the proper placementof the foil. Suggested instruments includescissors with straight, delicate blades; mold-ing tweezers with a straight, pointed tip; foilremoval tweezers with a serrated tip for anoptimal grip during the removal of foil; andan orangewood stick for consistent burnish-ing results.

Fig. 11-39

The platinum foil is cut into the specifiedshape using a template designed for veneer-ing techniques. The platinum foil shouldthen be placed over the labial surface withthe tab portion below the gingival margin.Any excess foil mesial or distal to the prepa-ration is trimmed.

Fig. 11-40

Fig. 11-41

The foil is held firmly in place and wrappedaround the mesial and distal margins of thedie using the straight, pointed-tip tweezers.

Fig. 11-42

The platinum foil is folded over the labio-incisal edge and carefully burnished from itscenter toward the proximal corners using anorangewood stick. This will create little in-cisal "wings" in the foil.

Fig. 11-43

Excess foil is burnished diagonally fromthe incisal wings to the middle third of thetooth to create a labial ridge. The foil ridgeshould be creased using the straight,pointed-tip tweezers.

The triangular tab of foil which extendsapically and the gingival margins of the prep-aration are then burnished to secure the foilto the die.

Fig. 11-44

Excess foil at the incisal wings is cut usingscissors, leaving a 1 mm extension. Thestraight, pointed-tip tweezers should be usedto grip the edge of each incisal wing. Thetweezers are then turned 180 degrees, fold-ing the foil wing in half.

Fig. 11-45

Fig. 11-46

Next, the labial ridge is burnished towardthe center of the preparation, flattening theexcess foil into place. This procedure willstrengthen the labial portion of the foil.

Fig. 11-47

The foil is secured incisally by flatteningthe foil at a 45 degree angle from the incisalwings toward the lingual midline.

Fig. 11-48

All excess foil beyond the mesial and distalmargins and the lingual-incisal edge shouldbe cut using a #11 scalpel.

In order to remove the foil from the die,the tab portion must be gently lifted in ahinge-like movement from the gingival mar-gin toward the incisal edge.

Fig. 11-49

The completed foil matrix represents aduplicate of the shape of the die to which itwas applied. When all foil matrix proceduresare carefully followed, the matrix will notbend or change shape.

Fig. 11-50

The foil matrix is then held above a cone-shaped flame of a bunsen burner, or a verticaltorch flame until the foil is bright orange.This procedure decontaminates and annealsthe foil to a dead soft state.

Fig. 11-51

Fig. 11-52

The annealed foil matrix is placed on thedie by positioning the matrix at the incisaledge and carefully lowering it into placeusing a hinge-like movement. The foil shouldbe lightly re-burnished onto the die.

The foil is secured to the die with a dot ofsticky wax at the mesial, distal, and apicallocations on the tab portion of the foil. Thedies should then all be returned to thepin-indexed base for the porcelain buildupand evaluation.

Fig. 11-53

Fig. 11-54

Porcelain specifically formulated for ve-neering techniques is recommended for op-timum esthetic results. Body porcelain oneshade darker than the prescribed shade isapplied from the gingival margin to justbelow the middle third of the labial surface.The gingival porcelain should be extendedinto the proximal curvatures to create a visualtrapezoidal effect.

The prescribed shade of body porcelain isapplied, feathering it slightly over the darkergingival shade. The build-up procedure iscontinued from the middle third to the in-cisal third with feathering strokes. Threelobes of the prescribed body shade porcelainshould be placed to create a mammeloneffect. In both interlobular areas thereshould be a small amount of gingival porce-lain shade for visual contour.

Fig. 11-55

Incisal porcelain is applied to the desiredlength of the restoration. The incisal build-upshould extend over the incisal edge to thelingual-incisal line angle. The porcelainbuild-up should terminate at the lingual-incisal line angle unless the lingual surfacehas been prepared by the dentist.

Fig. 11-56

Enamel porcelain is selectively appliedfrom the incisal edge to the middle third ofthe tooth to create the translucent effectnaturally found in this area. Either a brush oran instrument is used to form the labialanatomy, and light vibration is carefully em-ployed to condense the porcelain.

Fig. 11-5

Fig. 11-58

The foil is then lifted by the tab portion atthe base of the die in a hinge-like motion,lifting it away from the labial surface of thedie, up and off the incisal-lingual edge.

After bench setting for five minutes on asaggar tray, the porcelain with the foil matrixis fired.

Fig. 11-59

This chart shows the firing instructions forPVS porcelain, by Cercom International,Inc.

Fig. 11-60

The porcelain is fired to its full maturity onits first bake and should have a lustrous,stippled appearance. Color definition andnatural translucency are readily visible as aresult of the four stage porcelain buildup.

Fig. 11-61

The foil matrix and the covering porcelainare returned to the die for finishing andcontouring. A medium grit sandpaper disk isrecommended for trimming the margins andcontact points. Further finishing should beaccomplished with microfine friction-grip di-amonds (15 to 45 grit) and a high speedhandpiece. Marginal areas are contouredwith sandpaper disks. Flame-shaped dia-monds can be used for facial contour.

Fig. 11-62

Each die is replaced in the master modelsuccessively, until all contact points are ad-justed.

Fig. 11-63

A slurry mix of glaze is applied in a thinlayer on the porcelain surface to seal micro-porosities and create a vital luster. Stainsmay be applied at this time to add definitionand character. Stains are allowed to dry priorto the final glaze firing (1700 degrees F).

The serrated-edge tweezers are used toremove the platinum foil. The foil is grippedand peeled from the inner face of the veneerrevealing a smooth, glass-like surface. Theinner surface of the veneer must be etched tocreate a surface suitable for fusing to thetooth.

Fig. 11-64

The veneer is placed on a Mortite strip. Asuitable etching gel is thoroughly spreadwithin the concave inner surface of the ve-neer for the manufacturer's recommendedtime.

Fig. 11-65

A neutralizing solution is prepared and theveneer with Mortite strip is submerged inthe neutralizer.

After the veneer is cleaned in a soapysolution, the veneer intaglio is air abradedwith aluminous oxide and cleaned again be-fore final placement on the master model.

Fig. 11-66

When all the steps are carefully followed,the resultant porcelain veneers rival tradi-tional crown and bridge prosthetics in esthet-ics, fit, durability, and longevity.

Fig. 11-67

Fig. 12-2

These teeth are readily visible in mostsmiles, and occasionally the amalgam-cladocclusal surfaces themselves contribute tothe overall lack of esthetics.

Fig. 12-3

Thus it is easy to see why porcelain inlaysand onlays are popular with patients. In thiscase, for instance, the procedure was strictlyan elective cosmetic process. The offendingamalgams were removed, taking care to con-serve as much enamel and dentin as possible.

The teeth were then temporized normallyexcept for the choice of cement. Duringtemporization it is important to avoid usingany cement which contains eugenol, sinceeugenol can interfere with the subsequentbonding procedure.

Fig. 12-4

In these photographs of the completedcase, the gray tone of the bicuspids has beenreplaced by a natural, healthy appearance.Also note the shade incompatibility on themesio-buccal of the second bicuspid. In thiscase, a variability of luting composite shadeswould have been very helpful.

Fig. 12-5

The occlusal surfaces of the inlays demon-strate the artistry that the laboratory techni-cian can and should apply in the fabrication ofthese restorations.

Fig. 12-6

The list of reasons to employ fused porcelain inlays and onlaysgoes beyond simple esthetics. Porcelain restorations are muchmore conservative than complete coverage of full crowns. In thecase of porcelain inlays/onlays, the only parts of the tooth thatneed to be removed are the decay and the access zone. In thereplacement of amalgam restorations, only the old amalgam iseliminated; if there is no recurrent decay, all the healthy enameland dentin can be maintained.

When composite resin is used as the complete filling materialfor posterior restorations, the overriding concern is that thecomposite will wear faster than the surrounding tooth structure.When porcelain is utilized, this is no problem. In fact, theporcelain wears more slowly than the adjacent dental structures.'

In many ways, the porcelain inlay is proving superior even tothe gold inlay. The major weakness of the gold inlay is found atthe margin; the cement is much weaker than either the tooth orthe inlay. With this weakness, the gold inlay often failed becauseof marginal leakage and recurrent caries. Though current ce-ments are much improved, none can match the integrity of aporcelain fused to enamel interface.

Additionally, evidence is mounting that a porcelain restorationwhich has been fused to the tooth structure increases the tooth'sresistance to fracture. 2

It may come as a surprise to some that, as with several of ourstate of the art "high tech" modern dental techniques, theporcelain inlay is not at all new. Porcelain has been used in ClassV inlays since the last century. These simple inlays were evenroutinely etched on their inner surface by hydrofluoric acid, butwere held in place with zinc oxyphosphate cement. The neededadditional retention was afforded by placing a groove in the axialwalls of the tooth midway between the pulpal floor and theenamel margin. A similar groove also was cut into the porcelaininlay.

But simply being able to produce a porcelain inlay was notenough. In a Class V facial restoration, not only must the cementfulfill all the usual requirements (such as low film thickness, highadhesive strength, lack of toxicity, etc.), but also it must havesuperior esthetic qualities. Clearly, the early use of zinc oxyphos-phate to cement porcelain inlays resulted in esthetic restorationoutlined by an unesthetic ring. In addition, the need for a cementof minimal solubility is much more stringent with porcelain thanwith a burnishable material like gold.

These two problems were so severe that the porcelain inlaynever really achieved widespread acceptance. Still, the potentialof a dental restoration composed of porcelain was clear, andseveral dentists kept the torch lit over the next century.

Accuracy in manufacturing was a crucial issue, since this wouldminimize the demands upon the luting cement. Many manufac-turing techniques were developed and discarded over theyears.` These included compressing porcelain powder into amold and subsequently firing the porcelain, injection molding ofmolten porcelain, platinum and gold foil used as a matrix,utilizing preformed blocks of finished porcelain cut from dentureteeth as a matrix, as well as other innovative approaches. Overtime, the approach which seemed to come closest to the idealinvolved the use of an investment model. Still, until recentlyeven this technique was not usable for Class 11, 111 or IVrestorations.

It was not until 1986, when McLaughlin patented a techniqueutilizing a full statue of the tooth made of refractory material, thatthe laboratory phase of porcelain inlays and onlays became aroutine procedure.' ° A second method has also been patented byGreggs. This second method uses a platinum matrix instead ofthe refractory model".

With the resolution of the laboratory difficulties, the remainingproblems with porcelain inlays and onlays centered around thecement. Since porcelain fusing with composite resin was sosuccessful in the anterior regions, it seemed an obvious step toutilize the same techniques to hold porcelain inlays and onlays inplace. As a luting agent, composite could easily solve themechanical and esthetic problems, leaving only the possibility ofpulpal damage from the luting resin and poor adhesion to dentinto be solved.

In addition, the ideal handling characteristics of a luting resinfor inlays still had to be delineated since they are different fromthose of veneers. Both chemical and light cured materials havesignificant drawbacks in this application. A self curing compositetakes about four minutes to set in the mouth. This length ofsetting time can create difficulties in keeping the inlay in placeand in assuring adequate moisture control. Furthermore, themargins cannot be finished until the set is complete, for fear ofdisturbing the seating of the restoration. If there is a significantquantity of excess composite interproximally, it can prove verydifficult to remove since the material is very hard and theinstrument access almost impossible. The color match betweenthe tooth/porcelain/composite is often so good that the flash maybe difficult or impossible to identify, at least until it has causedserious periodontal problems.

This would seem to indicate that light cured materials shouldbe utilized; the dentist can seat the restoration at his leisure,eliminate excess material, and cure when ready. Unfortunately,the light from the curing unit does not pass through porcelainvery easily. Even a thin layer (1-2 mm) of relatively non-opaqueporcelain can diffuse the light to an extent that its curing capacityis severely curtailed. While the readily accessible margins are

usually cured to hardness, the underlying floors of the cavitypreparation and the pulpal walls of any boxes will often maintainuncured composite resin. A similar situation exists at any gingivalfloor of the deeper parts of the preparation. As a result, therehave been a number of early failures with porcelain inlays andonlays, and many practitioners have lacked the confidence andclinical assurance to continue with this mode of treatment.

Fig. 12-7

Almost as soon as glass ionomer materialssuch as Shofu Glass Ionomer Cement FillingMaterial-Type II were discovered, it wasclear that they were suitable for use as a baseunder fillings in all but the deepest places. Inthe case of porcelain inlays, these materialsare utilized to replace all the dentinal struc-ture that has been removed by decay oraccess, as well as the filling of the boxportions of interproximal preparation areas.Glass-ionomers are well tolerated by gingivaltissue, 12 and will bond to dentin." Further-more, after setting, they can be acid etchedfor subsequent bonding procedures. 14,15

By utilizing glass ionomer cement as an etchable base, thepractitioner can minimize the thickness of the porcelain which isdesirable since unnecessary thickness can often frustrate properlight-curing. The glass-ionomer can be built up to within 1-2 mmof the required occlusal height, and the laboratory fabricatedinlay/onlay will complete the remaining vertical dimension.There is little doubt that the stronger curing light units willpenetrate this thickness of porcelain as long as it is relativelytransparent.

There are still limitations for this approach, however. Theseinclude the degree of color change that can be effected with therelatively thin porcelain, the difficulty in temporizing such asmall volume of missing dental material, and the extremetechnique sensitivity involved. In addition, the bond strength ofglass ionomer to dentin is less than that achievable with thenewer dentin bonding agents, such as GLUMA (ColumbusDental, St. Louis, Mo.) and Scotchbond 2 (3M, St. Paul, Minn.).

In general, therefore, the most suitable material for theplacement of porcelain inlays/onlays is a dual-cure material; thatis, a composite bonding material whose setting is initiated bymeans of a conventional curing light and continues until comple-tion through a self-curing process. These materials are oftenreferred to as "continuous cure" materials because of this uniquecharacteristic. When attaching porcelain inlays using a dual-curecomposite resin, the margins can be externally light-cured toeliminate the possibility of leakage, and once curing is thusinitiated, all the remaining internal composite fusing material (aswell as those margins that are inaccessible to direct curing) setwithin a short time. There are a number of these dual-curematerials available currently, but unfortunately, they all lack arange of shades that cosmetic dentistry absolutely requires.

Still, there appear to be some very promising materials on thehorizon. These combine the properties of dual-cure, multipleshade availability, and true dentin bonding. With their advent,the use of cosmetic inlays/onlays is sure to increase and becomea part of every dentist's repertoire. While the future willcertainly see changes in the technique for porcelain inlays andonlays, it will also most assuredly see increased utilization of thisfine technique.

REFERENCES

1. Grossman, D.G.: Processing a dental ceramic by castingmethods. A presentation made at the Conference on RecentDevelopments in Ceramic and Ceramic-Metal Systems forCrown and Bridge, W.K. Kellogg Foundation Institute Grad-uate and Postgraduate Dentistry, University of Michigan,October 10- 12, 1983.

2. Causton, B.E., Miller, B.,Sefton, J.: The deformation ofcusps by bonded posterior composite restorations: an in vitrostudy. Brit Dent J 159:397. 1985.

3. Petrie, M.: The construction of porcelain inlays without theuse of foil. The Dental Gazette, 443-7, 1940.

4. Ehleider, A.J.: New porcelain inlay technique requires noplatinum matrix. Dent Survey, 20(6):1019-1022, 1944.

5. George, R.K.: Porcelain inlays baked in investment matrix.Dent Digest, 549-51, 1956.

6. Kinzer, R.L., Bonlie, D., and Mertz, K.: Preliminary report:high heat investments in constructing porcelain restorations.J Calif State Dent Ass., 30(9):314-17, 1962.

7. Mosteller, J.H., Wells, H.R., and Johnson, D.L.: Clinicaland laboratory procedures for class V porcelain inlays. J AlaDent Ass, 4(49):27-37, 1965.

8. Rochette, A.L.: Prevention des complications des fracturesd'angle d'incisive chez I'enfant: reconstitution en resine ou enceramique dont la retention n'est due qu'a I'adhesion. Entre-tiens de Bichat, Odonto-stomat. Paris 1972. Expansion Scien-tifique Francais, p. 109-114.

9. Rochette, A:A ceramic restoration bonded by etched enameland resin for fractured incisors. J Prosth Dent, 33(3)287- 293.March 1975.

10. McLaughlin, G.: Fabrication of porcelain restorations. U.S.Patent number 4,579,530. Applied Nov 21, 1984, issuedApril 1, 1986.

11. Greggs, T.: U.S. Patent number 4,473,353. Applied April15, 1983, issued Sept 25, 1984.

12. Wilson, A.D., Prosser, H.J. Biocompatibility of the glassionomer cements. J Dent Assoc S Africa, 37:872-879. 1982.

13. Negm, M.M., Beech, D.R., and Grant, A.A. An evaluationof mechanical and adhesive properties of polycarboxylate andglass ionomer cements. J Oral Rehabil 9:161-167. 1982.

14. Garcia-Godoy, F., Malone, W.F.P. The effect of acid etchon two glass ionomer lining cements. Quint Inter 17:621-623. 1986.

15. McLean. J.W., et al. The use of glass ionomer cements inbonding composite resins to dentine. Br Dent J 158:410-414.1985.

Several groups and publications have sprung up to helpanswer the need for continuing education in the area of Cos-metic Dentistry. Organizations such as the American Academyof Cosmetic Dentistry can help both the neophyte and experi-enced practitioner by serving as a network that shares develop-ments in the field. The reader is encouraged to avail himselfof these opportunities.

The future holds promise for better methods of attachmentand improved formulations of ceramics. In addition, new appli-cations of the technology are already being developed. Bondedinlays, onlays, full crowns, all porcelain bridges, orthodonticapplications, and other even more innovative applications arealready being developed.

Doubtless, by the time this book reaches your hands some ofits content will already have been superseded by newer, bettermethods.

This is how it should be.It is an exciting time in dentistry.

CHAPTER 13 CONCLUSION--AND THE FUTURE 237

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