color atlas of laminate porcelain veneers.pdf

Alilogo 2

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.

Alilogo 2

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.

Alilogo 2

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.

Alilogo 2

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.

Alilogo 2

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.

Alilogo 2

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.

Alilogo 2

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.

Alilogo 2

Alilogo 2

COLOR ATLAS OF PORCELAIN LAMINATE VENEERS

The significance of the teeth to smiling andto the face in general should not be underes-timated. Teeth contribute an important partto 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

Alilogo 2

CHAPTER I THE DEMAND FOR COSMETIC DENTISTRY

3

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.

REFERENCES1. Nierenberg, G.I., Calero, H.H.: How to Read a Person Like

a Book, New York, 1971, Simon and Schuster.

8


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 theuse of these veneers for a time. But theincreased use of plastic laminates brought tothe fore certain inherent problems with thistreatment modality. The most serious draw-back was an inadequate bond formed be-tween the composite bonding agent and theplastic laminate7 . This gave rise to delamina-tion, chipping, and marginal percolation.

Fig. 2-6

The entire laminate would often just popoff the tooth, as it did for this patient's lateralincisor. Some of these failures were due to aweak 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 itsoriginal shape at some time after.

Fig. 2-7

Any pressure at the marginal areaschipped off sizable segments of the plasticveneer, leaving portions of the underlyingcomposite exposed. The subsequent differ-ential staining was one of the major causes ofcosmetic 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.

Alilogo 2

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

14


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 VENEERSMichael 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

16

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.


17

REFERENCESl. 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.

Alilogo 2


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 ATTACHMENTThe basic technique of micromechanical attachment has

changed 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 ATTACHMENTThe 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

27

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 seconds2829. 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.

32


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.

REFERENCES1. McLaughlin, G.: Porcelain fused to tooth -a new esthetic

and 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.

34


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

35

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.

Alilogo 2


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 breakdownmay 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 growincorrectly, often as a result of crowdingduring the mixed dentition period. Theircosmetic treatment will sometimes includethe use of orthodontics.

Fig. 4-6

Lingual position. These malpositionedteeth 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

42

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.

CONTRAINDICATIONSThere are also a few contraindications for the use of porcelain

laminates. 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.

44


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 ANALYSISObviously, the first step in the fabrication of porcelain veneers

must 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 EVALUATIONThe objective evaluation is begun by comparing the shape and

the 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

Alilogo 2

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 90degree position. Here the problem is reversed. The bucco-lingual dimensions of the cuspid are greater than the mesio-distalones. Therefore, the veneered cuspid will appear too wide. Thiscannot be corrected by the reduction of the cuspid's dimensionsbecause this kind of preparation would destroy the interdentalcontacts and upset the occlusal harmony of the entire mouth.Fortunately, by adjusting the labial prominence of the cuspidmore mesially or distally, the apparent size can be controlled (seechapter 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 parameterdefinition before the procedure can be started.

The Bioform Tooth Form System gives a reading for theapproximate vertical height of the central incisor. This figure, inmillimeters, refers to the enamel portion of the crown from theincisal edge to the cervical dentino-enamel junction at themid-point of the tooth. This dimension, along with the previouslyestablished central incisor width and facial outline form, gives atotal picture of a tooth (and hence the entire anterior region) thatis in esthetic harmony with the patient's face.

If there is adequate vertical space to allow the required lengthfor the incisors, then the fabrication of the veneer is straightfor-ward. Should the necessary space be lacking, the laboratory willhave to resort to lengthening the teeth (or shortening them, asthe 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 achievingthis is to make the central incisors slightlylonger 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 fin

color atlas of laminate porcelain veneers.pdf

Documents