Minimally Invasive Porcelain Veneers and an All-Ceramic Crown
Meeting the esthetic challenge with an evidence-based approach.
Howard E. Strassler, DMD; Iona Kempler, DDS
Esthetics has been and will become even more important as a treatment modality consideration in dental practices.1 While much of the esthetic dentistry presented with bleaching and porcelain veneers is elective, there are those clinical situations where a tooth or teeth present in the esthetic zone has an existing crown that is defective. Dentists today have the opportunity to replace the defective crown and change the appearance of the adjacent teeth to improve their patient’s smiles. In some cases bleaching alone is adequate to lighten the color of the adjacent teeth to the crown before remaking the crown, but there are times a restorative intervention with porcelain veneers will provide the most predictable results, and can be achieved by placing a porcelain veneer over the existing unesthetic porcelain.
From an evidence-based standard, a minimally invasive approach using porcelain veneers has been demonstrated using LUMINEERS® (Den-Mat, http://www.denmat.com). The primary author has been following 30 patients with a total of 167 Cerinate LUMINEERS for over 20 years. At the last reported recall, there has been a 100% retention rate of the LUMINEERS with almost no change in color. It was reported that 94% of the veneers were clinically successful (157 of 167) with only 10 veneers needing replacement. Replacement was usually due to chipping or cracking on stress-bearing surfaces. These fractures were usually cohesive fractures within the porcelain.2 Currently, patients have been recalled for periods of over 24 years with no change from the long-term data previously reported.
The success of porcelain veneers is based on maintaining enamel as the bonding substrate for the veneers. Crispin has investigated the thickness of enamel in anterior teeth.3 Based on his findings, veneer preparations that have been recommended for some of the earlier pressed porcelains would leave the gingival third of the preparation primarily in dentin. Friedman did a 15-year retrospective study on porcelain veneers.4 He reported that adhesive fractures of the veneer bonded to enamel was rarely observed but that most failures related to cervical fracture and microleakage occurred when dentin was the bonded tooth substrate. Friedman further stated that veneer preparations should remain in enamel only. Research on the durability of dentin bonding has demonstrated a significant bond strength drop-off after 2 years.5-7 Miller also reiterated the message that enamel is precious when he stated that it is every clinician’s professional responsibility to preserve healthy tooth structure and remove only the byproduct of disease.8 Also, a 5-year clinical evaluation of periodontal assessments comparing teeth restored with porcelain veneers with preparation and no preparation demonstrate no difference in periodontal health.9
A 30-year-old man presented to the dental school with a desire to whiten his smile. A clinical evaluation revealed a defective crown on the maxillary left central incisor, tooth spacing of the maxillary anterior teeth with lateral incisor tooth width proportion discrepancies with the maxillary central incisors. Also, the patient was unhappy with the color of his teeth and the darkness of his gingival tissues adjacent to the porcelain-metal crown on tooth No. 9 (Figure 1). Matching a single crown to porcelain veneers can be challenging. Porcelain at different thicknesses has a different optical appearance and properties due to how light passes through the porcelain.10,11 When a crown is clinically acceptable other than the esthetics due to color or fracture, placing a porcelain veneer over that crown by bonding to the porcelain provides for the best color match to other teeth that are being restored with porcelain veneers.12 In those circumstances when teeth in the esthetic zone will have a mixture of ceramic crowns and porcelain veneers, it is recommended that a slightly more opaque porcelain be used to neutralize the optical differences in a thin porcelain veneer and a thicker porcelain crown.13 After discussing treatment alternatives including bleaching, crown replacement, direct composite resin bonding, and minimally invasive porcelain veneers, the patient accepted the most conservative treatment choice with the best esthetic result. It was decided that tray bleaching to change the color of the teeth would be done first before a final treatment decision would be made. After 2 weeks there was a noticeable improvement in the whitening of his teeth (Figure 2). After completing tooth whitening, the patient was then shown a diagnostic wax-up to demonstrate the esthetic changes that could be accomplished with minimally invasive porcelain veneers with LUMINEERS for the maxillary lateral incisors and right central incisor and an all-ceramic crown using Cerinate pressed porcelain for the left central incisor. The patient decided that only the four maxillary incisors needed an esthetic change. The treatment plan was initiated to place porcelain veneers for teeth Nos. 7, 8, and 10 and an all-ceramic crown for tooth No. 9.
The porcelain-metal crown was removed atraumatically by cutting through the porcelain of the crown with a medium-grit diamond and then through the metal with a metal cutting bur. The crown preparation was refined for tooth No. 9 and minimally invasive tooth preparations were completed for teeth Nos. 7, 8, and 10 (Figure 3). An impression was made using a bite impression technique with a fast-setting monophase vinylpolysiloxane impression material (examples include Take 1® , Kerr Corporation, http://www.kerrdental.com; Imprint™ 3, 3M ESPE, http://www.3mespe.com; Affinis, Coltène/Whaledent, http://www.coltene.com; Aquasil™, DENTSPLY Caulk, http://www.caulk.com) in a bite impression tray. The bite impression technique provides the laboratory with an accurate impression of the teeth to be restored, the opposing arch and bite registration. This technique guarantees accurate articulation of casts by eliminating the guesswork for the laboratory.14 A laboratory authorization was completed describing the purpose of the veneers for alignment, incisal widths and lengths, shade desired, and surface texture for the facial surface of the veneer. The diagnostic wax-up and digital photograph were also included. Because of the optical property differences between a thicker crown and thin veneer, a 50% opaque pressed porcelain was requested for restoration fabrication. A temporary crown was fabricated for tooth No. 9 using a prefabricated acrylic resin shell that was relined, adjusted chairside, and cemented. Teeth Nos. 7, 8, and 10 did not require provisional restorations because they were minimally reshaped.
The restorations were returned by the laboratory (Figure 4). Note that due to the thickness differences between the crown for tooth No. 9 and for the veneers for teeth Nos. 7, 8, and 10, there was an optical difference in tooth shade appearance between the crowns and veneers.
The temporary crown was removed and the teeth and surfaces to be bonded were cleaned with a water-pumice paste using a disposable prophylaxis angle. The interproximal surfaces were cleaned using a safe-side handled diamond strip. The teeth were then wetted with water and the veneers and crown were tried on the teeth to verify fit, esthetic shape, and evaluate color of the crown when compared to the veneers. Color try-in with try-in paste was done after the teeth were etched and adhesive applied.
Surface Treatments/ Restoration Try-In
The bonding of porcelain to the tooth surfaces is a multi-stage technique. It requires a variety of different reagents to optimize the bond to the porcelain and tooth. The internal surfaces of all the porcelain veneers were etched in the laboratory with hydrofluoric acid. Depending on the veneer cement system used, the sequencing of color try-in with the cement and surface treatments can vary. Some veneer cement try-in pastes are recommended to be used before any surface preparation of the porcelain or tooth, while other systems recommend all surface pretreatments be done before placement of the try-in paste. The sequence for the veneer cement system used for this case (UltraBond, Den-Mat) is described. At chairside, the etched surfaces of the porcelain had an acidic conditioner (Porcelain Conditioner, Den-Mat) painted on the surface with a disposable brush for 20 seconds. This step was not to etch the porcelain; that was done by the laboratory with hydrofluoric acid. The use of an acidic conditioner chemically activates and enhances the chemical treatment of the porcelain with an organo-silane (porcelain chemical coupling agent). The surface was rinsed with water and dried. The conditioned surface was then painted with a silane ceramic primer (eg, BIS-SILANE™, Bisco, http://www.bisco.com; Ceramic Primer, 3M ESPE; Clearfil Porcelain Bond Activator, Kuraray Dental, http://www.kuraraydental.com; Cerinate Prime, Den-Mat) for 30 seconds, then dried from the surface. A resin adhesive was then applied to the internal porcelain surfaces. The dental assistant then placed a resin-based try-in paste matched with the veneer cement in the same shade as the porcelain into the veneers and ceramic crown. While the veneers were being prepared for bonding, the four teeth to be restored were etched for 15 seconds with a phosphoric-acid etchant, as the preparations were in dentin. When the preparations are in dentin, it is important to etch the crown preparation for no more than 15 seconds. Enamel can be etched for a range of 15 to 60 seconds with no adverse bonding effects. The teeth were rinsed for 10 seconds with an air-water spray and then dried leaving an etched frosty appearance of the enamel. The dentin surface of the crown preparation was lightly wetted with water using a damp cotton pellet leaving the etched dentin glossy (Figure 5). The resin adhesive primer from a fourth-generation adhesive (eg, Tenure AB, Den-Mat; Adper™ Scotchbond™ Multi-Purpose, 3M ESPE) was applied with a Benda Brush (Centrix, http://www.centrixdental.com) to the etched tooth surfaces to be bonded. The crown and veneers with try-in paste were placed for patient acceptance and to evaluate the final shade. Because the crown is a different thickness for the veneers, there may be a shade variation that must be compensated for during the cementation. After patient acceptance the try-in paste was cleaned from the interior surfaces of the veneers and crown with brush wetted with an adhesive resin. The resin cement (eg, Ultra-Bond Plus, Den-Mat; RelyX™ Veneer Cement, 3M ESPE; Variolink Veneer, Ivoclar Vivadent, http://www.ivoclarvivadent.com) was then placed onto the veneers and crown. The teeth, veneers, and crown were now ready for a simultaneous placement technique.
Porcelain Veneer Placement
The three veneers and ceramic crown were bonded to place using a multiple placement no-matrix technique that has been described by Putter and associates.15,16 This technique has greatly simplified the placement of porcelain veneers. In other techniques, veneers are bonded to place either one or two at a time. When this is done, the composite resin cement must be finished at the proximal margins before the seating of adjacent veneers. This can be problematic. In some cases, finishing the interproximal margins of porcelain veneers can cause gingival hemorrhage that can interfere with subsequent continued bonding of the adjacent veneers.
The veneers were placed simultaneously on the teeth along with the ceramic crown. As each veneer was placed, the back end of the Benda Brush was used to fully seat the veneers. The same was done with the crown. Complete seating of the restorations was verified visually. Excess resin cement was removed using a brush wetted with adhesive bonding resin (Tenure S, Den-Mat) (Figure 6). This technique ensures that the resin cement will be at the margins of the veneers. Each veneer was tack-cured for 1 second with a 2-mm tacking tip using a high-energy curing light in the middle of the facial surface of each veneer (Figure 7). For LED and quartz-halogen curing lights with tacking tips, the time should be increased to 5 seconds. Using a small tacking tip for a short burst of time allows for easy clean-up of excess resin cement from around the veneer and crown margins and floss was gently passed between the proximal surfaces to allow for easy interproximal clean-up of excess cement (Figure 8).
After light-curing, removal of excess resin cement was accomplished with a scaler. A straight chisel can also be used. The margins were finished to remove any potential ledges with a flame-shaped diamond on a high-speed handpiece with air-water spray. This is critical to clinical success when placing bonded porcelain restorations. The remaining margins were finished with finishing diamonds and finishing burs (Figure 10). The porcelain-composite-tooth interface was then polished with porcelain polishing rubber abrasives (Jazz™, SS White, http://www.sswhiteburs.com).
Because no matrices were used during the veneer-crown placement, the contacts were then opened up for access using a non-abrasive intraoral dental saw, CeriSaw (Den-Mat) (Figure 11). The saw was used with a rocking motion to open and separate the contacts without removing any porcelain or tooth structure. This saw uses extremely thin, 0.05-mm stainless steel, sharp dental saw blades attached to a miniature hacksaw handle. By having the blades attached to the handle and with the placement of a gingival wedge, the saw was easily controlled preventing the accidental cutting of gingival tissues.15,16 It is not necessary to open all of the contact areas at the placement appointment. In some cases the more difficult to access proximal contacts can be more easily managed and opened up at a follow-up appointment. Tooth movement during function loosens those tight contacts to allow for easier access at the next appointment.
Interproximal finishing was accomplished with diamond interproximal finishing strips. The removal of resin cement and slight recontouring of the interproximal gingival surfaces were accomplished with a reciprocating handpiece (Profinet, Dentatus, http://www.dentatus.com) that is the same size as a disposable prophylaxis angle and fits on the straight nose cone of a slow-speed handpiece using a thin, flat-bladed, safe-sided diamond Lamineer tip (Dentatus) (Figure 12). Use of a thin diamond bur in the gingival interproximal areas with a high-speed handpiece can be risky because the veneers can be notched by the diamond in these areas, leaving an esthetically unsatisfactory restoration. The reciprocating handpiece accomplishes the task efficiently and effectively with little risk. The restorations were then polished using a disposable prophylaxis angle and cup with a diamond impregnated porcelain laminate polishing paste. When compared to the preoperative smile, the completed veneers and crown provided a highly esthetic result that thoroughly pleased the patient (Figure 13 and Figure 14).
Placing all-ceramic crowns and veneers together on adjacent anterior teeth in the esthetic zone provides a challenge due to differences in thickness and optical properties of the porcelain being used. This article describes the considerations when placing a hybrid case and the techniques that will provide for clinical success.
The porcelain veneers and all-ceramic crown were fabricated at Cerinate Smile Design Studios in Santa Maria, CA.
Dr. Strassler has received grant/research support from Den-Mat, Dentatus, SS White, Centrix, and DENTSPLY.
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About the Authors
Howard E. Strassler, DMD
Professor, Division of Operative Dentistry
Department of Endodontics, Prosthodontics and Operative Dentistry
University of Maryland Dental School
Iona Kempler, DDS
Division of Prosthodontics
University of Maryland Dental School