Cherilyn G. Sheets, Newport Beach, Calif.
in the use of porcelain
Porcelain veneer restorations including preparations, impression materials, cast materials, refractory casts, handling of porcelain, the try-in, and the final luting are discussed. Techniques are described to increase marginal accuracy, establish predictable natural polychromatic color within the porcelain, establish good contours and surface textures, and shorten final placement time. Tooth preparation is routinely recommended, as is the combination of epoxy dies, refractory casts, and anatomic buildup techniques. Emphasis is placed on a close working relationship and communication among the dentist, dental technician, and patient. (J PROSTHET DENT 1990;64:406-11.)
T he use of porcelain
laminate veneer restorations as an effective treatment modality has been well established.1-20 The allure of a conservative preparation, the potential for excellent esthetics, and the promise of healthy tissues have made the procedure popular. It is estimated that over 68% of general dentists have placed at least one laminate restoration.’ Unfortunately, laminate restorations are often believed to be simple esthetic procedures whereas, in reality, well-executed porcelain veneer restorations require substantial technical skill and accuracy by both the dentist and dental technician.3
Presented before the Pacific Coast Society of Prosthodontists meeting, Napa, Calif. 10/1/18813
OBJECTIVE This article discusses practical techniques in the placement of porcelain veneer restorations. Extensive trial-anderror chairside experience with the veneering procedure has provided the source of most observations and recommendations. A review of the literature on porcelain veneer restorations and discussion with colleagues have corroborated these observations. This article will discuss preparations, impression materials, cast materials, refractory casts, handling of porcelain, the try-in, and the final bonding.
Problems The problems associated with porcelain veneer restorations are poor marginal integrity,2,3 unesthetic monochromatic color,3* 4 unpredictability of cementing,4-6 inadequate tints and opaquers,4s 6*7 unnatural surface texture,13
1. Depth cutting instrument establishes amount of enamel reduction. 2. Remaining enamel is removed with two-grit diamond instrument.
3. Tooth preparation with interproximal extension to contact area for additional strength and modification of contour of veneer restoration. Fig. 4. Final polish of preparation margin using 12-fluted finishing bur. Fig. 5. Fabrication of incisal guide from provisional waxing of prospective veneer restorations on diagnostic casts. Fig. 6. Initial porcelain application using anatomic shading buildup technique. Fig. 7. Repositioning of refractory cast in incisal guide to confirm planned length and contour. Fig. 8. Reshapingfired porcelain to establish contour and surface texture before final firing. Fig.
Fig. 9. Individual finished restorations before placement. Fig. 10. Finished veneer restorations placed on master cast to confirm esthetic effect. Fig. 11. Transferring veneer restoration to tooth by using soft wax-tipped placement stick. Fig. 12. Removal of excess resin bonding material with soft brush moistened in composite resin. extensive placement time,49 6p8 potentially inadequate fee,‘? 4*6*g and unrealistic long-term expectations by the patient.Q 4
Preparations Some authors still regard tooth preparation as unnecessary for porcelain veneer restorations.8F lo However, most authors believe that a definite tooth preparation must be completed, ideally in enamel, with a chamfer preparation for adequate porcelain thickness.‘* 2,4y5ysylo-l3 In some instances, the preparation includes a rounded incisal edge and terminates lingually with a heavy chamfer.
Preliminary shades are selected before tooth preparation commences. Tooth preparation s&ts with a depth cutting diamond stone LVS-1 or LVS-2 (Brasseler Laminate Veneer System Set 4151, Brasseler USA, Savannah, Ga.), to establish the depth of enamel to be removed ,(Fig. 1). A
two-grit diamond stone (LVS-3 or LVS-4) is an effective way to remove the remaining excess enamel and finish the preparation (Fig. 2). For additional porcelain strength, the margins are extended interproximally to the contact area (Fig. 3).r3 The margins are then polished with a l%-fluted bullet-shaped finishing bur (Brasseler H283K016) (Fig. 4). Sandpaper strips are used interproximally to polish and assure minimal separation of the preparation for more accurate marginal detail. Only the margins of the preparation are polished. All internal portions of the preparation are left roughened for maximum bond strength.20 The margins of the preparation are placed slightly above the gingival margin.lW8, 11*l3 Tissue retraction is not usually necessary. For complete visualization, all preparations and finishing procedures are completed under magnification. A protective removable guard may be made for patient use on an interim basis. An irreversible hydrocolloid impression will allow making this guard by methods similar to ones used for provisional fixed restorations.21
Fig. Fig. and Fig. nor
13. Maxillary anterior restorations immediately after luting procedures. 14. Preoperative occlusal view of teeth with enamel fluorosis, interproximal caries, minor anatomic discrepancies. 15. Occlusal view of maxillary anterior restorations demonstrating correction of mianatomic discrepancies and establishment of normal labiolingual dimensions.
Impressions The use of a swaged platinum matrix has been described.13 Another technique included the combined use of reversible hydrocolloid impression materials, stone caste, and refractory models for porcelain veneer fabrication. However, after limited microscopic analysis, marginal integrity appears to be superior with the combined use of addition reaction silicone impression materials, epoxy dies, and refractory casts. Two or more complete arch addition reaction silicone impressions are made according to the manufacturer’s instructions. The number of impressions may vary with the number of preparations. Generally, for one to two veneers, two impressions are made; for three to six veneers, three impressions are made; and for seven to 10 veneers, four impressions are made. Impressions are examined under magnification to ensure an adequately reproduced preparation. Although only a single impression is theoretically required, multiple impressions are cost-effective in precluding the need to reappoint patients for corrected im-
pressions. At this time, tooth shades and specific esthetic requirements are reconfirmed. Pictures of unique shadings to be recreated are drawn.
Casts To prevent the problems commonly associated with dental stone casts, the use of epoxy (Oxydental Products, Inc., Hillside, N.Y.) casts made from addition reaction silicone impressions is recommended. Epoxy produces a smooth surface to the cast; there is no wear with use and no chipping of the cast during refitting; and when reproduced to form a refractory cast, the technique minimizes surface roughness.
Porcelain veneers made directly on a refractory die are less likely to warp and distort during the firing process; thus, a much better adaptation may be expected.14 Following the manufacturer’s directions on refractory materials often produces a cast with a slightly grey shade
(Gresco-Cerevest II, Gresco Products, Inc., Stafford, Tex.). Another material, Vita Hi Ceram refractory die material (Vident, Baldwin Park, Calif.), sometimes produces a green discoloration in the veneers. By slightly modifying the manufacturer’s directions, a white cast with no change in accuracy can be produced from Cerevest II. This cast causes no discoloration in the final veneers and seems to cause less porosity and microfractures. To control thermal contraction, the size of the refractory cast should be kept to a minimum. To produce a white refractory cast, the temperature and time are modified during the preburnout phase for degassing. By using 1400’ to 1450’ F for 30 minutes (or longer if the cast is extremely large), a white cast is produced. The maximum length of time a cast should be degassed is 1 hour. Margins are marked on the refractory cast with a refractory marking pencil (Whip-Mix V.H.T. Marking Pencil, Spectramark Refractory Making Pencil, Whip-Mix Corp., Louisville, KY.). The margins must be protected during this procedure. Because improper use can open the margin, stereoscope magnification should be used when marking the refractory cast. The line is often so thin that it can be seen only with magnification, especially after the porcelain is fired.
An incisal guide is made from the provisional wax-up by use of impression putty (Fig. 5). The refractory cast is placed in this incisal guide to aid in establishing the length and anatomy of the finished veneer. Twenty to 50 pm of porcelain powder are placed and fired on the refractory die. This porcelain veneer is developed with the anatomic shading technique described by Kuwata22 (Fig. 6). The refractory cast can be repositioned in the incisal guide as a constant reconfirmation of length and contour (Fig. 7). When the anatomic buildup has been completed, the porcelain is fired. Body, incisal, and sometimes translucent or effect porcelains may be added and fired to bring the veneers to full contour. A second layering of porcelains compensates for the shrinkage of the first firings and restores the veneers to full contour. The contour and surface texture is created before the final glaze, and the contacts are evaluated for insufficiencies (Fig. 8). Thin disks (Ultra-thin Multipurpose Abrasive Discs, National Keystone Products Co., Philadelphia, Pa.; Diamant Diamond H355F220, Horico Manufacturing Company, West Germany) are used under magnification to separate the refractory cast into individual dies. Margins are trimmed and contoured to final form. The veneers are made as smooth as possible with sandpaper disks and porcelain polishing wheels (Knife-edge Pre-Polish Wheel, Grey 24, B35-677,Vident). This finishing helpsto lower the final temperature required to achieve a smooth porcelain surface, which aids in eliminating microfractures and providessharpmargins.Insufficient contacts are corrected and the veneersare glazed. 410
The dies are divested asmuch aspossibleby useof carborundum points (Shofu Dura Green TC2iTC4, Shofu Dental Corp., Menlo Park, Calif.). Final divesting is accomplishedwith an air abrasiveunit usingglassbeadsat 20 poundsof pressureor lower. The lower pressureavoids damagingthe margins. After divesting, the fit and marginal integrity of the veneersare verified on the epoxy cast. Areas of excessiveinternal pressure are located with a colored powder spray (Occlude, Pascal Co. Inc., Bellevue, Wash.) and are corrected. After all veneersfit individually, they are rechecked collectively and the contacts are adjusted. The veneersare prepared for etching by covering the labial surface with sticky wax. Etching is accomplishedwith HFL acid (Stripit, National Keystone Products Co., Philadelphia, Pa.) for 30 secondsin an ultrasonic unit. Then the veneers are washedand neutralized in a solution of baking soda and water for 1 minute in the ultrasonic cleaner.The sticky wax is chilled with fluoromethane spray (Gebauer Chemical Co., Cleveland, Ohio), and removed from the veneer.
Try-in The porcelain veneersare refitted to the mastercast and etched with hydrofluoric acid to the margin. There should be no binding at the contact areas,and all marginsshould fit accurately. The patient may be shownthe veneer restorations on the master cast prior to their placement in the mouth (Figs. 9 and 10). The teeth are cleaned with plain pumice and water, rinsed thoroughly, and dried. All veneersare individually and collectively verified for fit and marginal integrity on the teeth. The veneersare placed temporarily with a thin coating of try-in paste (Den-Mat Try-In Paste, Den-Mat Corp., Santa Maria, Calif.). This pasteis usedasa stabilizing mechanismto verify esthetics and ensure that the bonding material will not appreciably changethe esthetics developedin the veneer porcelain. With this technique the bonding materials make only slight overall shade differencesgiving more predictable esthetic control to the dentist who no longer needsto rely upon easily mobile pastes in a trial-and-error, nonrepeatable placement technique. The patient is requestedto examinethe veneersand any concerns are addressed. The veneers are then steamcleaned, placed in the ultrasonic with acetone, dried, and the etching rechecked. The veneers are silane-treated to increasethe composite porcelain bond.4*5~8*11,13v l5
For the final bonding process,a central incisor or maxillary anterior tooth veneer is placed first. One tooth is bonded at a time, alternating from the right sideto the left side of the mouth. If two central incisorsare involved, they are completed first. The tooth is isolated with interproxima1mylar strips, dead soft matrix, or artis shim stock. The tooth enamelis etched (30 to 60 seconds),washed(30 to 40 seconds),dried with dry oil-free air, and reisolated. Any exposeddentin is treated with a dentin bonding adhesive. OCTOBER
The tooth and veneer are coated with a thin coating of bonding agent and not polymerized. A thin, even coat of the chosen bonding composite material is placed on the etched surface of the veneer. A microfill composite resin is a useful bonding material because it allows a complete seating of the veneer. Christensen* stated that it also produces a more stable, highly polishable, stain-resistant margin. Some authors favor a small particle-size hybrid composite resin because it has the advantages of a microfill but reflects light more effectively than a pure microfill.13 The veneer is carried to position on a cottonwood stick with synthetic occlusal plane wax (Harry J. Bosworth Co., Skokie, Ill.) at the tip, seated gently to the margin, and held securely (Fig. 11). Excess material is removed gently with a brush lightly moistened with resin or composite resin as recommended by Tay et a1.2 (Fig. 12). This procedure reduces the “dragging out” tendency and ensures a smooth margin that is polishable. The use of a modified rubber tip is an alternate technique. Once the margins are cleaned, the veneer is exposed to the polymerizing light source for the first time. Polymerization is accomplished by exposing each labial quadrant of the veneer to the polymerizing light, followed by a center polymerization on the labial surface. Next, the veneer is polymerized on the interproximal and incisal aspects of the lingual surface. Since it is impossible to overpolymerize and easy to underpolymerize, longer polymerizing times are indicated. Dual polymerization materials assure a complete polymerization process but may slightly discolor with time. Minimal finishing is required if the margins fit precisely and the bonding material has been thoroughly cleaned with a sable hair brush at placement. Hand instruments (Brasseler Composite Cutting Hand Instruments 150.18,150.19, 150.20, Brasseler USA) may be all that are required. If more extensive finishing is required, satin finishing diamonds may be used (Brasseler ET Diamonds), followed by disks and a polishing paste. Contact with the porcelain should be avoided because studies indicate it is extremely difficult to repolish the porcelain margin once the glaze is disturbed.2* l1 Fine sandpaper and composite resin strips followed with a polishing paste may be used to finish the interproximal margins. All surfaces should be checked with thin unwaxed dental floss to confirm that no excess material remains. This process is repeated for each veneer in an alternating fashion from right to left. Once again, magnification is essential from etching to the completion of polishing. After final bonding and finishing of the last veneer (Figs. 13 through 15), the occlusion is carefully observed and adjustments are made where indicated. If the patient is
known to have parafunctional occlusal habits, a soft splint (Healthco Mouthguard Material .150 in., Healthco Inc., Boston, Mass.) is made for immediate use, and impressions are made for a hard resin protective occlusal splint.*> l1 The patient is given a mirror to examine the results, and advised not to place any force on the veneers for 24 hours to ensure that maximum bonding strength has been achieved.
SUMMARY This article has discussed chairside and laboratory techniques that replace the monochromatic, ill-fitting, unnatural veneer with a precise, natural-looking veneer that has a maximum probability for longevity. REFERENCES 1. Levin RP. The future of porcelain laminate veneers. J Esthet Dent 1989;1:45. 2. Tay WM. Lynch E, Auger D. Effects of some finishing techniques on cervical margins of porcelain laminates. Quintessence Int 1987;18:600. 3. McLean J. Ceramics in clinical dentistry. Br Dent J 1988,164:187. 4. Nasedkin NJ. Porcelain laminants: current perspectives on esthetic restorative dentistry: part I. Can Dent Assoc J 1988;54:248. 5. Bertolotti RL. Indirect veneers. J Calif Dent Assoc 1988,13:37. 6. Gross JS, Malcmacher LJ. Comparing porcelain laminate veneers to laboratory resin veneers-report of a case. Trends Tech Contemp Dent Lab 1988;5:28. for “inlayed” ceramic laminates on anI. Exner HV. Tooth preparation terior teeth. Tydskr Tandhielkd Ver S Afr 1987;42[VZY]:302. 8. Clyde JS, Gilmore A. Porcelain veneers: a preliminary review. Br Dent J 1988;164:9-14. 9. McComb D. Porcelain veneer technique. Ont Dent 1988;65:25. 10. Nixon R, Ibsen R, Freedman G. Cosmetic roundtable. Dentistry Today, April 1989. 11. Friedman M. Multiple potential of etched porcelain laminate veneers. J Am Dent Assoc 1987;116(Special issueh83E. 12. Millar BJ. Porcelain veneers. Dent Update 1987;14:381. 13. Garber DA, Goldstein RE, Feinman RA. Porcelain laminate veneers. Chicago: Quintessence Publishing Co Inc, 1988. 14. Hunt PR. Porcelain laminate systems. In Tay WM, ed. General dental treatment. Brentford, England: Kluwer Pub1 Ltd, 1986;1-14. 15. Nicholls JI. Tensile bond of resin cements to porcelain veneers. J PROSTHET DENT 1988;60:443-7. 16. Goldstein RE. Diagnostic dilemma: to bond, laminate, or crown? Int J Periodont Rest Dent 1987;7:9. 17. Sorensen JA, Torres TJ. Improved color matching of metal-ceramic restorations. Part III: innovations in porcelain application. J PROSTHET DENT 1988;59:1-7. 18. Nasedkin JN. Porcelain posterior resin bonded restorations: current perspectives on esthetic restorative dentistry: part II. Can Dent Assoc J 1988;54:499. 19. Sheets CG. Modern dentistry and the esthetically aware patient. J Am Dent Assoc 1987;116(Special issue):103E. 20. Aker DA, Aker JR, Sorensen SE. Effect of methods of tooth enamel preparation on the retentive strength of acid-etch composite resins. J Am Dent Assoc 1979;99:185-9. 21. Rieder CE. The use of provisional restorations to develop and achieve esthetic expectations. Int J Periodont Rest Dent 1989;9:123. 22. Kuwata M. Theory of practice for ceramo metal restorations. Chicago: Quintessence Publishing Co Inc. 1985. Reprint requests to: DR. CHERILYN G. SHEETS 360 SAN MIGUEL DR., ST. 204 NEWPORT BEACH, CA 92660
*Christensen GJ. Personal communication.