Case Selection for Porcelain Veneers Ching Chiat Lim*

Case selection for porcelain veneers Ching Chiat Lim*

The options for correction of unesthetic teeth are numerotis: among these treatments, porcelain veneers have received substantial attention from the profession and patients. The increase in dental health awareness and advances in dental materials and technology, such as the acid-etching technique, improved physical properties of composite luting resin, and the use of silane coupling agents, have contributed to the success ceramic veneers enjoy today. However, no single material or technique is ivlthout its limitations. This article therefore aims to review the criteria for case selection and the limitations of porcelain veneers in restorative dentistry. (Quintessence Int 1995:26:311-3¡5.)

Introduction Uses of porcelain veneers Management of noncarious surface defects Patients often request cosmetic improvements in their teeth. Frequently, such an improvement also improves Porcelain veneers can be used for the management of the patients' sense of well being and self-esteem. How noncarious defects, such as localized enamel malfor- well an individual looks is often a contributory factor mations and hypoplasia. Porcelain veneers have been to success or failure in life in today's highly competitive suggested for the treatment of eroded teeth^ and societies. enamel hypocaicification.' However, bonding of A porcelain veneer is a thin facing, about 0.5 to veneers to poor-quality enamel might lead to marginal 0.7 mm thick,'- covering the labial aspects of anterior leakage and the eventual failure ofthe restorations. teeth and the buccal aspects of some premoiar teeth. Masking of discoloration Veneers can be fabricated from traditional feldspathic Discoloration arising from fluorosis, tetracycline stain- porcelain or other ceramic materials, such as castable ing, or necrosis can be treated with porcelain veneers, or machinable glass ceramics. The veneer is then provided that the stains are not too dark. Limitations bonded to the enamel surface by mechanical and should always be recognized. Staining arising from chemical means. The mechanical attachment is achieved fluorosis can usually be treated successfully with by etching the enamel and the porcelain. The resin ceramic veneers when the surface enamel is removed composite is then allowed to form a strong micro- during tooth preparation (Figs I to 3). mechanical bond similar to that achieved with enamel.^ An additional chemical attachment to the porcelain Repair of structural defeets interface is accomplished by silane bonding.* Studies Horn* suggested the use of porcelain veneers to repair have shown that etching the porcelain surface is of fractured incisai edges, to correct mild malalignment of greater importance to overall bond strength than is teeth, to achieve closure of diastemas, and to restore using a silane coupling agent alone.^ peg-shaped lateral incisors. It is the author's opinion that resin composite may be a better materiai for cases that require only minimal replacement of tooth struc- • Lecturer. DepartmenlofRestorative Dentistry. National University of ture. This is because a tooth preparation of some kind Singapore, Faculty of Denlistij. Singapore. is required for a porceiain veneer, no matter how small Reprint requests: Dr Ching Chiat Lim. Lecturer, Department of the tooth preparation, to allow enough bulk of Restorative Dentistry, National University of Singapore, Faculty of Dentistry. 5 Lower Kent Ridge Road. Singapore 0511, Singapore. porcelain at the margin for strength. On the other

QuinWásence International Volume 2s. Number 5/1995 311 Esthetic Dentistry

Ftg 1 Severe tluorosis ¡s evident on the maxillary anterior Fig 2 The dark discoloration has been removed alter teeth. intraenamei preparation for porcelain veneers was com- pleted.

is required but placement of a post core is contraindicated. Repair offractured porcelain facings on fixed prostheses Millar' suggested the use of porcelain vetieers to repair fractured porcelain facings on fixed partial dentures. This is only possible if the other aspects of the prosthesis are satisfactory and otily the porcelain facing requires replacement. Otherwise, it is better to replace the whole prosthesis. Replacement of old resin composite veneers Porcelain veneers are frequently indicated for the Fig 3 Six maxillary anterior porcelain veneers are cemented. replacement of old resin composite veneers, with staining and wear being the most common complaints from patients. Orthodontic retainers hand, replacement of tooth structure with direct resin composite can easily be achieved without any tooth Porcelain veneers have also been used as orthodondic retainers to close postorthodontic diastemas."*" This preparation, making the procedure more conservative. works by maintaining tooth contact with the adjacent Tooth preparation is necessary for porcelain veneers tooth, thus preventing the reappearance of spaces. The because it provides the ceramist with a definite margin long-term stability of this form of retention is un- for finishing. However, when a few teeth are siightly known. Applications of this new concept are exten- tnalaligned, involving full labial buildup, porcelain sive, but care must be taken to evaluate the hmits of this veneers involving some tooth preparation may be more technique with adequate long-term chnical studies. esthetic and durable than direct resin composite Clinical observations have also confirmed that veneers, which consume more clinical time. etched porcelain veneers are ideally suitable for Porcelain veneers can also be used for the correc- tnandibular incisors if adequate interincisal space tion of cosmetic or minor functional needs in adoles- exists and the correct tooth preparation design is cent's teeth. Crown preparations on adolescent teeth chosen for the required occlusion.'^ are difficult because ofthe risk of infringement on the large, immature pulp by too deep a shoulder prepara- Criteria for case .selection tion,^ Porcelain veneers are also indicated in endo- Patients who are selected to receive porcelain veneers dontieally treated teeth in which esthetic improvement or any other restorative work, should have good oral

312 Quintessence '"'"mntinnnl Vnlr itmhnr.i'ijor. Esthetic Dentistry hygiene, healthy gingival tissue, and no occlusal composite, it is preferable to mask areas of marked disharmony.'-' The placement of porcelain veneers is discoloration with opaque or intensive porcelain (Vita an irreversible procedure because ofthe neccessity for Alpha porcelain. Vita Zahnfabrik). Precise instruc- tooth preparation. Therefore, the criteria for porcelain tions to the laboratory technician regarding areas of veneers must be carefully reviewed before the proce- marked discoloration are therefore crucial. A photo- dure is undertaken. graph of the prepared tooth is usually helpfiil if an in-house technician is not available. The use of resin Síi7í/f and dynamic occlusal relationship composite to mask marked discoloration is usually Long-term studies have indicated that porcelain ve- inadequate, because the resin is usually too translucent neers seldom delaminate.'^''' The usual mode of failure to have any masking effect. is fracture of comers; this frequently happens at the incisai edges. It is therefore important to analyze the Extent of caries static and dynamic occlusion before tooth preparation. Caries, if present, should be minimal. If little or no The occlusion will dictate the choice of tooth prepara- enamel is left after caries removal, placement of a tion design (not discussed in this article). The incisai porcelain veneer is usually contraindicated, Tiiis is porcelain finishing line is determined by the contact because tbe thin veneer is strengthened by bonding relationships between the incisors and canines in with the underlying etched enamel. The veneer-tooth centric and eccentric positions."" The margins should complex is weakened when the surface area of enamel be placed so they do not contact the opposing dentition available for bonding is decreased by 50%,'^ during the rest position.' Ideally, occlusal contacts during centric occlusion and lateral excursion should be Extent of restoration on porcelain or tooth strucmre completely. Occlusal A restoration, if present, should be smail enough that interferences and parafunctional habits are contraindi- the area for bonding with enamel is not compromised. cations for porcelain veneers, because they will result in The cavity design of the restoration should incinde crack formation and eventual fractureofth e restoration, margins that end in enamel, where possible. The old restorations should be replaced if the underlying caries Periodontal and oral health stattis status is questionable. A healthy periodontium fonns a strong foundation on Quality' of tooth which all restorative work will rest. It also facilitates ease of impression taking, cementation, and future If the amount of enamel for bending is compromised maintenance. It is therefore important to assess the due to any ofthe factors above, a veneer shell crown or patient's overall periodontal and oral health status conventional crown may be indicated instead of a before the procedure is begun, Mouthbreathers who veneer facing. have poor gingival health are poor candidates for Structural defects, such as amelogenesis imperfecta porcelain veneers. and dentinogenesis imperfecta, that leave insufHicient enamel and tooth structure for bonding are a definite Condition of tooth contraindication for veneer. Degree of discoloration Teeth with iarge areas of exposed dentin are unsuitable for porcelain veneers. However, small areas If the tooth is grossly discolored, it maybe necessary to of exposed dentin may be treated with dentinal bleach the tooth before the veneer is placed. However, bonding agents or glass-ionomer cements. the unpredictable stability of bleaching poses the problem of the return of discoloration beneath the Patients motivation to tnaintain porcelain veneers once they have been cemented. The patient's attitude toward dental health care should Usually, the discolorarion in tetracycline staining be assessed before porcelain veneers are attempted. A becomes more severe as the enamel is reduced. Such vigilant home care program and regular recalls are cases may require masking of areas of marked disco- important to maintain the longevity ofthe restoration. loration with opaque glass-ionomer cement or opaque porcelain. In either case, the parient should be warned Patient's expectations ofthe compromised esthetics whereby the veneers may The patient's expectations should be realistic. A appear opaque. Because the bond strength between diagnostic waxup may be required to demonstrate glass-ionomer cement and resin composite is not as areas of limitations when porcelain veneers are to be predictable as that between etched enamel and resin used for correction of mild malalignment.

Q ui ntessefloerlniemQttonoi Number 5/1995 313 Esthetic Dentistry

Orai habits preparation (Ironside JG. personal communica- Tlie presence of oral habits, such as nail or pencil tion, 1992) or dimples in the cenicr of the biting, is a contraindication for veneers because the preparation.'* shearing stress may be too great for the ceramics to 3. The dental laboratory costs involved may make withstand.'* the restoration more expensive to produce and thus less appealing to the patients." Advantages of porcelain veneers 4. Margina! adaptation of most veneers is about 1Ü0 |im or more. '^''^ Very lew with a marginal accuracy The porcelain veneer is usually fabricated in tht; of less than 20 \xm have been achieved.' laboratory. It therefore utilizes the ceramist's expertise in creating a lifelike restoration, and relies less on the 5. Thin sections of porcelain tend to be monochro- artistic skill ofthe dentist to individualize and charac- matic and lack the break up of color present in terize the veneers, as is required with direct resin natural teeth. Ifthe veneer is too translucent, areas composite veneers." Compared with the resin laminate of marked discoloration may show through; veneer, the porcelain laminate veneer also has the however, a more opaque porcelain buiidup may following advantages:* produce a high-Vaiue, monochromatic veneer, lacking in transiucency and dentinal contrast.^ 1. Color stability and lifelike appearance 6. It is ven,' difficult to match the shade of a single 2. Maintenance of luster porcelain veneer to the rest of the dentition. In 3. Higher resistance to abrasion, staining, and the such a case, a direct resin composite veneer may deleterious effects of alcohol, medications, and be preferred to the porcelain veneer. other solvents 4. Biocompatibility with gingival tissue 7. The bonding procedure is very technique sensitive 5. Increased chemica! and mechanical bonding to and time consuming. resin composite 8. Diagnosis of caries underneath cemented porce- 6. Less clinical chairside time lain veneers is difficult (Wlson NHF, personal communication, 1994). When two or more veneers are indicated, direct 9. It is difficuh to replace and repair porcelain resin composite veneer may be more lime consuming veneers when they fail (Wilson NHF. personal to fabricate. It would be more eificient to indicate communication, 1994). porcelain veneers for such cases, provided that the other criteria are met. 10. Acidulated phosphate fluoride and stannoiis fluoride should be avoided on porcelain veneers because both the porcelain and resin composite Limitations of porcelain veneers silica may be affected.-' 1. Changes in the color, length, contour, and contact areas of porcelain veneers fabricated by the Conclusions refractory die or platinum foii technique are The success of porcelain veneers depends very much limited,* because no reglazing or firing is possible on the method of fabrication and, most importantly, with either technique. Tlie veneers have to be case selection. Because some of the research in this remade or modified with ctalored luting cements field has been based on personal preference and when the shade is incorrect, and the success of anecdotal information, more objective research is shade modification with luting cement is highly required so that porcelain veneers will become fully questionable. However, when the veneers are accepted by both the profession and the public as an fabricated with the castable DICOR (Dentsply) alternative treatment in the field of conservative leucite-reinforced ceramic press system (IPS Em- dentistry. press. Ivoclar} or the copy milling system (Celay, Mikronat), postadjustment staining and reglazing are possible. References 2. Stabilization at try-in stage is difficuh because 1. Millar BJ. Porcelain venoms. Dent update. l937:Nov:331-390. there is no tensofrictional grip." However, this 2. Faunce VR. StmcttJred ceramics for laminate veneers, CDS Rev difficulty can be overcome by making a defhiite 3. Clyde JS. Cilmour A. Porcelain veneers: A preliminary review Br incisai step on the labial surface of the veneer Dent J 19SS:i64;9-l4.

314 Quintessence International Volume 26, Number 5/1995 Esthetic Dentistry

4. Quinn F, McConnell RJ, Byrne D. Porceiain laminate; A review. Br David Korson DentJ I985;i6l:61-6.í. 5. CalaniLa JR. Simonsen RJ. EfTect of coupling agents on bond strength oietciied porcelain | abstract 79]. J Dent Res Í984;o.l: 179. Aesthetic Design 6. Reid JS, Simpson MS. Taylor GS. Using porcelain veneers to treat for Ceramic Restorations eroded teeth. Dent Abstr Í99I:36:255-2S6. 7. BoksmanL, Jordan RE. Suzuid M, Gahl KA, Burgoyne AR. Etchtd porceiain labial veneers. Ont Dent I985;62; 1I-Í9. he most S. Horn HR. Porcelain laminate veneers bunded to etched onam«! TiiLittiral, Dent Ciin North Atii Í98.1;27:671-6a4. esthetic results 9- McLean JW. The science and art of denta! ceramics. Opcr Dent 199l;t6:t49-i56. in (iental 10. Hunt NP. Hypodontia-problems of pertiianent space dosure Br J ceramics can Orthod Í983;I2:I49-Í52. be achieve(] 11. Reid JS, Stirrups DR. A new solution to a dlíTicult problem of orthodontic retention Br J Ortho l9S7;i4:28t-283. with contem- t2. Freedman G, Ibsen R. Nixon R. Cosmetic roundtable: When to prep poraty techniques—atid rhis book describes or not to prep: Three costnetic dentists debate. Dent Today i989;S:22,24,26-27 passitn. how. Investigated are the characteristics of 13. Reid JS, Murray MC. Powers SM. Porcelain venccrs-A fuur year natural dentition, tissue tnanagement, impres- follow up. Rest Dent 19KS.4:6Ü-66. sions, occlusal records, waxino- techniques, t4. Caiamia JR. Clinical evalgatioti of etciied porcelain vcnccrs. Am J color, and kboratoty technit^ues, including Dent 1939:2:9-15. 15. Gougouiakis A. Murrranr WH, Barbakow I-. Lutz F. Retention rate methods for an aesthetic ceramic margin, and margin adaption of Cerec veneers ir vitro. In; Mörmann WH opalescence, and development ofthe dentine (ed). Proceedings of an International Symposium on Computer Restorations: State of the Art of the CEREC Method. Chicago; tnamelon. Klled with practical tips, this book Quintessence, 199L:537-545. is ideal for dentists and technicians. 16. Heyde JB, Cammarato VT A restorative system for repair of defects in anterior teeth: The laminate veneers Dent Ciin North Am t98l;25:337-345. US$78 17. Greggs T. Laboratory procedures [n: Garber DA. Goldstein RE, 159 pages; 292 color tllus; ISBN I-B5097-034-3 Feinnian RA |eds¡. Porceiain Laminate Veneers. Chicago: Quint- essence. l9R8:fiO-KI. iS. Dicor Clinical Instruction Manual. York, PA: Dentsply, 1984. Í9. Tay WM. Lynch E, Auger D. Effects of some finishing techniques on Contents cervicai margins of porcelain laminates. Quintessence Int 1987;i8:599-602. 1 Studies nl Natural Denticinn 20. Cerutti A. Marginai adaption ofCerec veneers in vivo. In- Mörmann WH (ed). Proceedings of an international Symposium on Computer 2 Dcnrisr-lcchmciati-Paticnt Communication Restorations: State of the An of the CEREC Method. Chicago: 3 Tissue Management for Aesthetic Quititessence, 199t:5í3-557. and Biological Harmony 1\. Essig ME. IsenbergBP. Leinfelder KF. Liu PR In vitro evalution of Cerec veneers utilizing standardized preparation template. In: 4 Impressions and Occlusal Records Mörmann WH (cd). Proceedings of an International Symposium on Computer Restorations: State ofthe An ofthe CEREC Method. 5 Aesthetic Wax Diagnostic Control Chicago: Quintessence, 1991:547-552. 6 Accurate Registration and Communication 22. Harasani MH. Isidor F. Kaaber S. Marginal fit of porcelain and indirect composite laminate veneers under in vitro conditions. Scand of Colour Characteristics J Dent Res 1991^99:262-268. 7 Advanced Laboratory' Techniques 23. SorensenJA,Stmt?:JM,AveraSP, Materdomini D. Marginal ñdelity and microleakage of porcelain veneers made by two techniques. J 8 Case Studies ProsthelDent I992;67.16-22. 24. Sim C, Ibbetson RJ. Comparison of Tit porcelain veneers fabricated using different techniques. Int J Prosthodont i993;6;.í6-42. 25. LitiiCC, Ironside JG. An in vitro study of the marginal adaptation of two ccraniic veneer systems labstract 74|. J Dent Res i994;73:746. Order Now 26. Lim CC. The Marginal Adaption of 3 Ceramic Veneer Techniques Toll free 1-800-621-0387 IMDS thesisl- Sydney. Australia: Univ of Sydney. 1993. Fax 708 682-3288 27. Yaffe A, Zalkind M. The effect of topical appiicatjon of" fluoride on booh/ composite restorations. J Prosthet Dent i981:45:59-62. p Quintessence Publishing Co, Inc

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