Clinical Experiences
With Bonded Porcelain
Laminate Veneers

Bonded porcelain veneers can provide successful esthetic and functional long-term service for patients. The purpose of this article is to describe the authors' clinical experiences with veneers over the past decade and to outline the procedures required to achieve predictable success with this conservative esthetic restorative modality. It is hoped that the authors' experiences and those of others will encourage practitioners to consider more routine use of this type of restoration in many of their more complex reconstructive cases.

Article copyright 1998 Journal of the California Dental Association.
Photographs copyright of the authors.

In the early 1980s, the bonded porcelain veneer was introduced to the profession amidst considerable skepticism regarding its potential for longevity in the harsh oral environment. ^1,2 Since that time, longitudinal studies as well as personal experience have demonstrated that these restorations can provide extremely successful esthetic and functional long-term service for patients. Based on this initial positive experience with bonded restorations, more-extensive applications have been used cautiously with certain patients in the past several years, and again the results achieved have been gratifying.

The purpose of this article is to describe the authors' clinical experiences with veneers over the past decade and to outline the procedures required to achieve predictable success with this conservative esthetic restorative modality. It is hoped that the authors' experiences and those of others will encourage practitioners to consider more routine use of this type of restoration in many of their more complex reconstructive cases.

Figure 1. Typical tooth preparation for porcelain laminate veneers illustrating the conservative nature of the preparation.

Bonded porcelain veneers have a number of significant advantages over either metal-ceramic or all-ceramic crowns.7-9 One of the most important advantages is that they are extremely conservative in terms of tooth structure (Figure 1). Metal-ceramic crowns require reduction of 1.2 mm of tooth structure on the labial surface and 1 mm on the lingual. Most all-ceramic restorations require 1.5 mm of reduction circumferentially around the tooth. Bonded veneers require only 0.5 mm reduction on the labial surface, and usually none on the gingival two-thirds of the lingual surface.

It has become increasingly apparent that conservation of tooth structure is a major factor in determining the long-term prognosis of any restorative procedure and that the extensive reduction of tooth structure required for conventional restorations is a major contributing factor in the rather high long-term failure rate often experienced with them.

Another remarkable advantage of porcelain veneers is their durability. As long as sufficient tooth structure remains to provide adequate support for the bonded porcelain and sufficient enamel remains for retentive purposes, the incidence of fracture is very low. ^10-13 This may well be a result of the tooth's ability to resist flexure because of the minimal tooth reduction required, although more research is necessary in this area.

Figure 2. The soft tissue response to veneers is almost universally excellent because of the supragingival placement of the cervical margins as seen on both central incisors.

An additional major advantage of porcelain veneers associated with these minimal reductions is lack of potential for pulpal involvement. Similarly, the periodontal response with porcelain veneers is outstanding (Figure 2).14-19 This is primarily because the restorations can blend in imperceptibly with the cervical tooth structure thereby allowing the cervical margins to be kept in a supragingival position.20 Optimally, these cervical margins should be placed in enamel; however, with contemporary dentin bonding systems, margins can be successfully placed on dentin/cementum when necessary.21 Also important to excellent periodontal response is the fact that overcontour of the restoration is not required to obtain esthetics (when proper tooth preparation is done).

Figure 3. Preoperative view of severe tetracycline stained teeth. Figure 4. The teeth in Figure 3 have been restored with porcelain laminate veneers. Although the final result is not perfect, it is a significant improvement over the preoperative appearance, and minimal tooth structure has been removed.

Excellent esthetics can be achieved with minimal reduction because of the exceptional covering ability of the porcelains used (Shofu Opal Porcelain, Shofu Dental Corp., Menlo Park, Calif.), the scattering effect of the luting resin (Opal Luting Composite, 3M Dental, St. Paul, Minn.), and the fact that there is no dark metallic oxide that needs to be masked by bright opaque porcelains (Figures 3 and 4). It is important that the clinician understand the limits of the porcelain veneer restoration in improving esthetics with extremely dark, stained teeth, such as in severe tetracycline staining. Because of the lack of thickness of the porcelain, the final result in these cases is often compromised, with the veneers exhibiting very high value and lack of vitality because of the use of underlying opaque porcelains (Figure 4). In these situations, metal-ceramic crowns may be the restorations of choice. With less severe staining, good results with porcelain veneer restorations can be obtained with slightly more aggressive tooth preparations.

One of the keys to success with bonded porcelain veneers is adequate tooth preparation. Many clinicians have advocated little or no preparation. This will most certainly lead to inferior esthetic results and may well compromise strength and the periodontal response.

Figure 5. A depth-gauging instrument is useful in controlling labial reduction.

Labial reduction of 0.5 mm is recommended, terminating in a chamfer margin in a slightly supragingival location. A depth-cutting diamond (Brasseler USA, Savannah, Ga.) is useful for providing the proper depth reduction (Figure 5). ²² If the tooth is to be neither lengthened nor shortened, the incisal edge is reduced 0.75 mm to 1 mm, and the lingual surface of the tooth reduced 1 mm past the prepared incisal edge. The lingual finish line is in the form of a shoulder 0.5 mm in depth.

On maxillary teeth, the location of the lingual finish line is determined by whether the mandibular incisors are to be restored. If the mandibular teeth are to be restored with crowns or veneers, the finish line on the maxillary teeth is carried gingivally past the point of centric occlusion contact with the mandibular incisal edges.

Figure 6. When the opposing teeth are not restored, the lingual finish line on maxillary veneers is 1 mm past the prepared incisal edge, permitting natural tooth contacts in maximum intercuspal position.

If the mandibular teeth are not going to be restored, the lingual finish line is 1 mm from the prepared incisal edge as stated previously (Figure 6). Carrying the preparation over the incisal edge limits the path of placement of the veneers but has two important advantages. The veneers can be more esthetic when this is done, and incisal translucency can be created if indicated (Figure 7).

Figure 7. Reducing the incisal edge allows for reproduction of natural translucency.

The second potential advantage is that some clinicians feel such veneers may be stronger than veneers that terminate at the incisal edge, and the incidence of fracture and/or debonding due to shear stress may be reduced.

Teeth can be lengthened using bonded porcelain veneers. ²³ In determining just how much a tooth can be lengthened, the lessons learned with metal-ceramics can be used. The critical guideline is that there should never be more than 1.5 mm of unsupported porcelain, whether the porcelain is supported with enamel or metal. In certain cases, teeth have been lengthened by as much as 2 mm, but in these cases the patients are informed that there is a calculated risk. Teeth that need lengthening of more than 2 mm require crowns. Occlusal considerations may modify these guidelines in specific clinical situations.

Bonded porcelain veneers have been traditionally used to esthetically restore discolored teeth, teeth with multiple composite resin restorations and malposed teeth, and to correct space problems such as a diastema. More recent indications for veneers are to develop anterior guidance prior to reconstruction of the posterior teeth and to restore moderately worn dentitions. This has been accomplished numerous times in the past several years, and use of veneers in these situations is now considered routine treatment, provided that sufficient tooth structure remains to support the bonded porcelain.

When veneers are to be used to establish anterior guidance in conjunction with a posterior rehabilitation, a specific sequence of treatment should be followed. First, diagnostic casts should be mounted in an articulator of choice and a diagnostic wax-up completed. This will give an indication of the amount of tooth lengthening required to establish function and the desired esthetic result. It will also indicate whether it is desirable to increase the vertical dimension. This wax-up can be duplicated in gypsum and a polypropylene matrix fabricated on the duplicate cast. Tooth-colored photo-cured acrylic resin can be used to form a try-in restoration to preview the final esthetic result prior to irreversible tooth preparation.

As shown in Figures 8A and B, recall of a patient one week after cementation often will allow detection and removal of slight amounts of excess tooth-colored resin cement. Usually minor irritation of the soft tissue will disclose the location of the excess cement.

In the majority of reconstructive cases, it is preferable to establish the anterior guidance first, and then to complete the posterior rehabilitation with cusp inclines in harmony with the established anterior guidance. Generally this will entail preparation of the 12 anterior teeth at one appointment. The final, optional, step in preparation of the veneers is the breaking of interproximal tooth contact using diamond-impregnated strips. Removal of the interproximal contacts facilitates laboratory steps but necessitates the fabrication of provisional restorations, which is readily accomplished using a clear matrix and light-cured acrylic resin (Unifast, G.C. America, Scottsdale, Ariz.). Impressions are made in a (poly) vinyl-siloxane impression material and the veneers are fabricated in the laboratory. Research has demonstrated that use of the platinum foil technique for fabrication of the veneers results in optimum marginal interity. ^24-26

Use of a medium to high viscosity resin luting agent (Opal Luting Composite, 3M Dental, St. Paul, Minn.) is highly recommended.27 Many clinicians believe this type of agent provides superior esthetics because of light scattering, strength, and optimal wear resistance. Most importantly, it also makes cleanup of the excess resin infinitely easier than when lower viscosity luting resins are used. The veneers are first tried in with water to determine the optimum shade match with the adjacent teeth. If the shade match is perfect, then a clear resin can be used for final cementation. If the shade need to be modified, chemical cure resins can be evaluated until fit and color are approved. Then, the resin is removed and the veneers cleaned using acetone and water. The teeth are then etched, and the veneers are cemented in place using the matching light-cured resin. When six anterior veneers are placed, generally, the centrals are cemented first, then the cuspids, and finally the lateral incisors.

Figure 9A. This "before" photo shows a patient on whom veneers were placed on both the maxillary and mandibular anterior teeth. The restorations were placed to increase the vertical dimension and to provide anterior guidance for a posterior rehabilitation. Crown lengthening was also done to aid in the final esthetic result. Figure 9B. The "after" photo.

When cementing a veneer with this type of luting agent, the restoration can be pressed into place, and the proper fit verified. Then, the incisal one-third can be exposed to 10 seconds of light to tack it in place. At this point, almost all excess cement can effectively be removed using a gold foil knife or sharp scalpel, without the risk of removal of cement from under the margins of the veneer. The rest of the veneer is then exposed to sufficient light to completely cure the resin cement.

Figures 10A and B show the posterior restorations in the patient shown in Figure 9. Metal-ceramic crowns with porcelain buccal margins were placed on the premolars and complete gold crowns on the molars.

With the authors' patients, a strict recall protocol is followed to ensure that all the excess cement is removed. The patient is appointed one week after cementation, and any areas where small amounts of tooth-colored cement remain are detected using inflammation of the gingival tissues as an indicator (Figures 8A and B). The patient is then recalled again one week later for additional evaluation. Usually the tissue will be immaculate at this appointment, but occasionally one or more additional areas of irritation are disclosed. As stated previously, the soft tissue response to porcelain veneers is generally outstanding once all excess cement is located and removed.

Once the anterior veneers have been luted in place, the posterior reconstruction can proceed in a conventional manner. If the vertical dimension has been increased using the veneers (Figures 9A and B), posterior support must immediately be provided by means of an occlusal splint and later with quality provisional restorations followed by the definitive crown restorations. (Figures 10A and B).

As shown in Figures 11A and B, a metal-ceramic crown with a porcelain labial margin was placed on the right lateral incisor, while both central incisors and left lateral incisor were restored with porcelain veneers.

Often patients present with anterior teeth requiring restoration in which some teeth can be restored with veneers but insufficient tooth structure remains on others so that crowns are indicated. Many clinicians have stated that it is not advisable to mix veneers and crowns, as a precise color match is not possible using such dissimilar materials. The authors' experience has been that it is possible to mix and match veneer and crown restorations (Figures 11A and B). The authors prefer to complete the metal-ceramic restorations first and then match the veneers to the result obtained.

Figure 12A. This patient requested lengthening of his central incisors. Figure 12B. An overlay acrylic resin shell provisional was fabricated to preview the anticipated result. Figure 12C. The overlay acrylic resin shell provisional is tried on the teeth and the correct length ascertained through esthetics and phonetics prior to any preparations.

For patients who have a high esthetic demand and require porcelain veneer restorations, an overlay acrylic resin provisional shell can be fabricated prior to initiating tooth preparation. This shell often helps predict the final esthetic result, and can be modified using esthetics and phonetics and then used as a guide for the laboratory technician (Figure 12A). A diagnostic wax-up of the proposed increased length is made on the diagnostic casts. The cast is duplicated, and an overlay acrylic resin shell provisional is fabricated (Figure 12B). This overlay shell is then clipped onto the unprepared teeth and evaluated for proper esthetics and phonetics (Figure 12C). At this time, the patient may take the overlay provisionals and evaluate the new length at his or her convenience and elicit a response from family members and friends. Once the length has been accepted by the patient, treatment can continue with confidence by the patient, dentist and laboratory technician with everyone fully understanding the final treatment objectives with respect to length, contour, texture and color (Figures 12D through F).

Figure 12D. The central incisors have been prepared and the lateral incisors slightly lengthened with direct composite resin. Figure 12E. The acrylic resin shell provisionals have been relined and placed over the preparations without temporary cements. Figure 12 F. The final restorations have been in place for one month.

It is important to keep in mind that veneers have definite limitations. ²⁸ They should not be used when insufficient enamel remains to provide adequate retention. Large Class IV defects should probably not be restored with veneers because of the large amount of unsupported porcelain and the lack of tooth-colored backing. The amount of unsupported porcelain should be carefully evaluated in cases with a large diastema before committing to restoration with veneers. Darkly stained teeth are not optimally restored with veneers as explained previously. The prognosis for veneers in bruxing patients has been the subject of much speculation. Certainly, bruxing patients at a minimum should be instructed to use a night guard after final restoration.

Summary and Conclusions

More than 10 years of experience have established bonded porcelain veneers as a predictable functional and esthetic restorative service. Use of such restorations in major reconstructive cases has proven successful and is indeed indicated. Veneers can also be successfully mixed and matched with conventional metal-ceramic crowns when indicated. Clinicians are encouraged to consider bonded porcelain for the routine restoration of anterior teeth.

Authors

George C. Cho, DDS, is an assistant professor and director of clinical education for advanced education in prosthodontics at the University of Southern California School of Dentistry.

Terry E. Donovan, DDS, is an associate professor and executive associate dean at the USC School of Dentistry. He is also chairman of the Department of Restorative Dentistry and co-director of advanced education in prosthodontics.

Winston W.L. Chee, BDS, is an associate professor and the Ralph W. and Jean L. Bleak Professor of Restorative Dentistry at the USC School of Dentistry. He is also director of implant dentistry and co-director of advanced education in prosthodontics at USC.

References

1. Horn HR, Porcelain laminate veneers bonded to etched enamel. Dent Clin North Am 27:671-84, 1983.

2. Calamia JR, Etched porcelain facial veneers: a new treatment modality based on scientific and clinical evidence. NY J Dent 53:255-9, 1983.

3. Crispin BJ, Full veneers: the functional and esthetic application of bonded ceramics. Compendium 15:284-8, 1994.

5. Nixon RL, Mandibular ceramic veneers: an examination of diverse cases integrating form, function and aesthetics. Pract Periodontics Aesthet Dent 7:17-26, 1995.

6. Hornbrook DS, Porcelain veneers: optimizing esthetics while re-establishing canine guidance. Compend Contin Educ Dent 16:1190-4, 1995.

7. Friedman MJ, The enamel ceramic alternative: porcelain veneers vs. metal ceramic crowns. J Cal Dent Assoc 20:(8)27-33, 1992.

8. Friedman MJ, Current state-of-the-art porcelain veneers. Curr Opin Cosmet Dent 1993:28-33.

9. Pippin DJ, Mixson JM and Soldan-Els AP, Clinical evaluation of restored maxillary incisors: veneers vs. PFM crowns. J Am Dent Assoc 126:1523-9, 1995.

10. Strassler JE and Nathanson D, Clinical evaluation of etched veneers over a period of 18 to 42 months. J Esthet Dent 1:21-8, 1989.

11. Calamia JR, Clinical evaluation of etched porcelain veneers. Amer J Dent 2:9-15, 1989.

12. Jordan RE, Suzuki M and Senda A, Clinical evaluation of porcelain laminate veneers: a four-year recall report. J Esthet Dent 1:126-37, 1989.

13. Karlsson S, Landahl I et al, A clinical evaluation of ceramic laminate veneers. Int J Prosthodont 5:447-51, 1992.

14. Friedman MJ, Multiple potential of etched porcelain laminate veneers. J Am Dent Assoc special issue Dec 1987:83E-7E.

15. Christensen GJ and Christensen RP, Clinical observations of porcelain veneers: a three-year report. J Esthet Dent 3:174-9, 1991.

16. Reid JS, Kinane DF and Adonogianaki E, Gingival health associated with porcelain veneers on maxillary incisors. Int J Paediatr Dent 1:137-41, 1991.

17. Garber D, Porcelain laminate veneers: 10 years later. Part 1, Tooth preparation. J Esthet Dent 5:56-62, 1993.

18. Dunne SM and Millar BJ, A longitudinal study of the clinical performance of porcelain veneers. Brit Dent J 175:317-21, 1993.

19. Kourkouta S, Walsh TT and Davis LG, The effect of porcelain laminate veneers on gingival health and bacterial plaque characteristics. J Clin Periodontol 21:638-401, 1994.

20. Materdomini D and Friedman MJ, The contact lens effect: enhancing porcelain veneer esthetics. J Esthet Dent 7:99-103, 1995.

21. Lacy AM, Wada C et al, In vitro microleakage at the gingival margin of porcelain and resin veneers. J Prosthet Dent 67:7-10, 1992.

22. Nattress BR, Youngson CC et al, An in vitro assessment of tooth preparation for porcelain veneer restorations. J Dent 23:165-70, 1995.

23. Wall JG, Reisbick MH and Johnston WM, Incisal-edge of porcelain laminate veneers restoring mandibular incisors. Int J Prosthodont 5:441-6, 1992.

24. Sorensen JA, Strutz JM et al, Marginal fidelity and microleakage of porcelain veneers made by two techniques. J Prosthet Dent 68:448-20, 1992.

26. Sim C and Ibetson R, Comparison of fit of porcelain veneers fabricated using different techniques. Int J Prosthodont 6:36-42, 1993.

27. Costello FW, porcelain veneer adhesive systems. Curr Opin Cosmet Dent 1995:57-68.

28. Sheets CG and Taniguchi T, Advantages and limitations in the use of porcelain veneer restorations. J Prosthet Dent 64:406-11, 1990.

To request a printed copy of this article, please contact/George C. Cho, DDS, USC School of Dentistry, Los Angeles, CA 90089-0641.