Clinical Evaluation of Castable Ceramic Veneers Douglas M . Barnes, D.S.S., M.S.," Lawrence W.Blank, D.D.S., M.S.," James C . Gingell,D.D.S., M.S.," and Mark A. Latta, D.M.D. t
Laboratory fabricated veneering of discolored or malformed anterior teeth is becoming a widely used technique. Etched Dicor and Dicor Plus ceramic veneers cemented with Dicor LightActivated Cement with Fluoride is one technique available to the practitioner. The purpose ofthis study was to evaluate the clinical effectiveness of castable ceramic veneers and the cementation system. Forty-three Dicor and 18 Dicor Plus veneers were placed in 12 patients. An intraenamel preparation was completed with a bullet-nosed diamond bur in an ultra-speed handpiece with airwater spray, and a polyvinylsiloxane impression was made. All veneers were fabricated on dies by the same laboratory technician and placed by one practitioner. The restorations were examined by two evaluators at baseline, 3 months, and 1year, using modified Ryge criteria.
ver the past 18years, dentists have veneered teeth using various techniques to correct esthetic problems without resorting to full coverage crowns. The many materials and techniques available for veneering may be divided into the following three categories: (1) free-hand placed, direct composite resins; (2)preformed acrylic laminates: and (3)laboratory fabricated acrylic resins, microfill composite resins, porcelain, castable glass ceramic veneers, and Dicor Plus veneers (Dentsply International, York, PA). Glass ceramics, originated by Corning Glass Works in the early 1950s,were introduced to the dental field in 1977 by Mr. Peter Adair, a dental technologist from Boston, Massachusetts. Castable ceramics were marketed as a joint venture by Dentsply International and Corning, Inc. Cast ceramics are successfully used as cookware, radomes for guided missiles, boundary retainers for space shuttles, and floor tiles for buildings. Castable ceramic technology used in dentistry for the fabrication of crowns, inlays, onlays, and veneers is available to the profession under the trade name of Dicor.2 Glass ceramics are fabricated by the unique combination of investing and eliminating a wax pattern, then casting liquid molten glass into the mold and later converting to a ceramic material by heat treatment of the glass. This process causes an internal nucleation and crystallization within the ceramic, creating a material
that is machinable. The crystalline phase consists of tetrasilicone mica crystals within a glass matrix. Maturation and crystalline growth occurs during a process called ~ e r a m m i n g .Castable ~.~ ceramic veneers are fabricated by this process. The introduction of castable glass ceramics to dentistry brought several distinct advantages not only to the dentist, but also to the dental technician and patient. Clinical studies to date demonstrate that castable ceramic crowns and veneers are strong, durable, esthetic, and periodontally sound restorations."1° A close match in translucency between cast ceramic material and enamel gives these restorations a natural a p p e a r a n ~ e . ~ Further, castable ceramics have the potential for color stability in the oral environment. Their color stability is a definitive improvement over preformed acrylic laminate and composite veneers, which tend to discolor over time.11-13 Flexural strength tests of castable ceramics indicate a modulus of rupture of 22000 psi as compared to porcelain (13.000psi), dentin (7500 psi), and enamel (1500psi).5When bondingveneers or inlays, the etched castable ceramic and composite resin cement combination is similar in bond strength to etched porcelain and composite resin. This flnding suggests that etched castable ceramic with composite resin adhesive has the bond strength necessary for a successful veneer restor a t i ~ n . Clinical ~ . ~ trials are in progress with favorable evaluations reported at 4 years.14 Castable ceramic veneers bonded with Dicor luting material have less microleakage than Mirage porcelain veneers (Myron's Dental, Kansas City, KS) bonded with composite resin cement.15 The same study also indicated that Dicor veneers had consistently poorer fit than Mirage veneers. However, use of the lost wax technique in fabrication of the veneer results in a very accurate ~ a s t i n g . ~
'Baltimore College of Dental Surgery. Dental School. University of Maryland at Baltimore. Baltimore.M q l a n d tDentsplylntemaUonal.York.Pennsylvania Address reprint requests to Douglas M. Barnes. D.S.S., M.S., Baltimore CollegeofDentalSurgery. DentalSchool.UniversityofMaxylandatBaltimore, 666 W. Baltimore Street, Baltimore. MD 21201 0 1992 Decker Perlodicals Inc.
JOURNAL OF ESTHETIC DENTISTRY VOLUME 4.SUPPLEMENT 1992
The clinical procedure was based on the technique described by Barnes and c0lleagues.l’ To obtain an optimum esthetic result, the labial intraenamel preparation consisted of a .50- to .75-mm reduction of the incisal third of the crown, tapering to .25 mm in the gingival third. If moderately stained teeth were being prepared, an additional .25 mm in the incisal two thirds and .10mm in the gingival third was reduced to allow for increased thickness of the veneer for opaquing purposes. The preparation was accomplished using a bullet-nosed diamond bur in an ultra-speed handpiece with air-water spray coolant. The incisal edge was incorporated into the preparations if indicated by esthetic or occlusal requirements (e.g., edge-to-edge occlusion). If the incisal edge was included in the preparation, the finish line was extended lingually. Incisal reduction was approximately 1.5 mm to allow for adequate bulk of restorative material. The incisal edge was not included in the preparation design if sufficient labiolingual tooth thickness remained to ensure adequate strength. Following preparation, the teeth were carefully cleaned and dried prior to final impression. The impression was made using Reprosil (L.D. Caulk Company, Milford, DE) impression material. Syringingwas carried out to assure an accurate reproduction of both the prepared and unprepared tooth structure at, or slightly below the gingival margin. Gingival retraction was used to facilitate making an accurate impression. A shade was selected using the Trubyte Bioform Color Ordered Shade Guide (Dentsply International). Conventional Dicor veneers were used for nine patients whose esthetic requirements demanded a translucent restoration. Dicor veneerswere used to correctminor staining or discoloring problems (Figs. 1,2,and 31, diastemas (Figs. 4,5, and 61, and malalignments. Dicor Plus veneers were used for three patients who had severe tetracycline staining. The Dicor Plus veneers were used because they have the potential to mask dark stains more effectively than conventionally shaded Dicor veneers. The veneers were fabricated by a licensed dental laboratory. The laboratory returned the veneers etched and heat-treated with a silane coupling agent.2o The veneer insertion and cementation were accomplished using the investigational cementation system now marketed as Dicor Light Activated Cement with Fluoride. Included with this system is a single catalyst and a series of three shaded opaquing cements plus one translucent (neutral) cement. Also included with the kit are four shade matching, water-soluble try-in pastes. The try-inpastes were used to verify the accuracy of the selected cement shade prior to etching and final cementation. When using the try-in pastes on the veneers, the operator always started with translucent and incrementally added the necessary shaded try-in paste to achieve the desired results. The try-in paste ratio was recorded. After isolation with cheek retractors, the teeth were pumiced in order to clean all tooth surfaces to be bonded. Cementation was performed one tooth at a time starting with the central incisor to act as a guide for the subsequent teeth. The central incisor was separated
Castable ceramics are well tolerated by gingival tissue. Savitt and co-workers reported clinical trials demonstrating that well-maintained castable ceramic restorations promote a microbial environment consistent with nondestructive periodontal conditions by inhibiting bacterial colonization.s They also noted approximatelysevenfold fewerviable bacteria colonize cast ceramic restorations compared with the number found on natural contralateral teeth.8 The clinical technique for castable ceramic veneers is based on an intraenamel preparation initially described by Barkmeier and associates16and later modified by Barnes et al. l7 This technique, although irreversible, produces the following advantages: (1) restorations are not overbulked facially, maintaining the palatolabial arch form; (2) normal tooth contour occurs in gingival areas: and (3)there are definite marginal finish lines. Another advantage is improved color masking by the restoration as a result of increased veneer thickness made possible by the preparation design. Castable ceramic veneers are generally more translucent than porcelain veneers. Therefore, porcelain veneers have the potential to mask stains more effectively than castable ceramic veneers and therefore may be used for very dark stained tetracycline teeth. The porcelain veneer opacity is built with a body material. The color is intrinsic throughout the laminate. In contrast, castable ceramic veneers, when conventionally shaded, have colorationon the surface that is approximately 100 microns thick. To maximize the benefits of both materials, Vryonis and Geller18.19 developed a veneer restoration using a combination of castable ceramic plus layered porcelain. Marketed as Dice? Plus, this laminate veneer system uses a thin undercasting of castable ceramic with an external .3 to .8 mm of porcelain. This system relies on the mica-containing castable ceramic for accurate marginal adaptation, underlying translucency and reflectivity, and the porcelain surface for masking darkly stained teeth. Few long-term clinical trials exist evaluating castable ceramicveneers. The purpose of this ongoing study is to evaluate the clinical effectivenessof Dicor and Dicor Plus veneers cemented with an investigational dualcured, resin cement now marketed as Dicor Light Activated Cement with Fluoride (Dentsply International/ York Division). The evaluations were completed for baseline, 3-month, and 1-year intervals. Additional recall evaluations are planned.
METHODS AND MATERIALS The sample was selected from the University of Maryland Dental School patient population. Each patient in the study had one or more of the following esthetic concerns: (1)multiple diastemas: (2)discolored teeth: (3) misproportioned teeth: (4) discolored or unesthetic existing restoration: or (5)misalignment of anterior teeth. Only anterior teeth were included in the study, and each tooth had enamel for bonding. 22
Castable Ceramic Veneers
Ngure 1. Preoperative view of patient 1 with minor staining
Figure 4. Preoperative view of patient 2 with multiple diastemas.
and a diastema.
Figure 6. Patient 2: baseline view of castable ceramic
Ngure 2. Patient 1: baseline view of Dicor veneers.
Ngwe 6. Patient 2: 1-year recall.
Figure 3. Patient 1: 1-year recall.
JOURNAL OF ESTHETIC DENTISTRY VOLUME 4. SUPPLEMENT 1992
desired esthetic result. The viscosity of the cement was appropriate allowing for removal of excess with a sable brush prior to curing with a light. The fluoride content and biocompatibility of the cement was appreciated for the potential to prevent recurrent caries and postoperative sensitivity. Postoperative sensitivity was not reported during the course of the study. The try-in pastes caused transient sensitivity in non-anesthetized prepared teeth when dentin was exposed. This occurrence may be attributed to the osmotic pressure differences between glycerine in the try-in pastes and fluid in the dentinal tubules. Dentsply International reports that cytotoxicity studies indicate the try-in paste is not harmful to the pulp, and sensitivity did disappear when the try-in paste was rinsed off. The water-soluble try-in pastes gave a clinically acceptable prediction of the final cement shade. The three shaded cements were very high in value and chroma, which in our experience is an advantage for cementing crowns, and a disadvantage for cementing veneers. Increased thickness of crowns over veneers necessitates a cement with intense chroma and high value in order to allow for the shade modification of the crowns by the cements. In order to compensate for high value and intense chroma when cementing the veneers, translucent try-in paste was used first. If a modification in color or opacity was necessary, shaded try-in pastes were incrementally added to the translucent paste until desired esthetic results were achieved. In several cases, the company-recommended try-in paste shade did not give the most ideal clinical result. The recommended tryin paste shade was modified with another shade 30%of the time to achieve the desired result (see Fig.7). Translucent cement was used in the majority of the veneer cases. The 1-year evaluation provided information on color stability and postoperative sensitivity. At this time the veneer/cement complex appeared color stable, and no patients reported postoperative sensitivity. All the veneers were clinically acceptable; there have been no failures. Two veneers have fracture lines in the ceramic
from the adjacent teeth with a n ultra-thin Dead Soft Matrix (Den-Mat, Santa Maria, CA). The tooth was then etched with 37 to 50% phosphoric acid gel for 15 to 30 seconds.21After the tooth was rinsed and lightly dried, the etched enamel was inspected to ensure a dull frostywhite appearance. Universal Bond 2 (L.D.CaulkCo.) was used as the bonding agent prior to cementation if dentin was exposed. Moon and Duling reported that veneers placed using a dentin bonding agent in addition to composite cement had less microleakage than veneers placed with only composite cement.22The dentin bonding agent should be air thinned and precured prior to cementati~n.~~ The shade of the final cement selected in the try-in stage was dispensed with equal portions of base and catalyst. The ratio selected for the try-in paste was duplicated as closely as possible with the final cements to achieve the shade previewed with the try-in pastes. The dual-cured cement was mixed and cured according to the manufacturer's instructions. After placement and curing of the veneer, excess cement was removed with a Brasseler 3 150.28 and 29 carbide-tipped composite carver (Brasseler USA Inc., Savannah, GA), and the margins were finished and polished using conventional composite polishing and finishing instruments as necessary. Interproximal finishing was accomplished with sandpaper strips. Oral hygiene instructions were given and a n evaluation was completed prior to releasing the patient .24 Two examiners evaluated the restorations by direct means at placement using modified Ryge (1971)criteria (see Table 1).Three-month and 1-year evaluations were completed, and further yearly recalls are planned. The evaluation parameters include veneer color match on the model to the shade tab: veneer color match to the shade tab on the tooth with trial paste; veneer match to the shade tab after final cementation; marginal adaptation; interfacial staining: secondary caries; and postoperative sensitivity. Disagreements between examiners were resolved by consensus. Preoperative, baseline, and 1-year recall photographs were taken.
Forty-three Dicor veneers and 18Dicor Plus veneers were placed in 12 patients. All the restorations were evaluated at baseline, 55veneers and three crowns were evaluated at 3 months, and 55 veneers and four crowns were evaluated at 1 year. The results of the clinical evaluations are shown in Figures 7 to 10.
A n investigational cement was used in this study. Several positive clinical observations can be made regarding the investigational cementation system. The number or shades available (three shaded cements and one translucent cement) was sufficient to obtain the
RYGE CRITERIA Alpha
Figure 7. Results of the clinical evaluation of veneer to shade tab try-in paste using Ryge criteria.
Castable Ceramic Veneers
f i f l l I I
M A T C
Table 1. Modified Ryge Criteria
Category and Rating
Color match Alfa Bravo
Matches shade tab in color/shade. Mismatches shade tab in color/shade by less than one shade tab gradation. Mismatchesshade tab in color/shade by one shade tab gradation or more.
0 Base Iine
Marginal adaptation Alfa No visible evidence of a crevice along the margin into which the explorer will penetrate. Bravo Visible evidence of a crevice along the margin into which the explorer will penetrate or catch. Charlie Explorer penetrated into crevice, reaching dentin, or base is exposed. Delta Restorationis mobile, fractured or missing. Cavosurfacemarginal discoloration Alfa No discoloration anywhere on the margin betweenthe restoration and the tooth structure. Bravo Discolorationpresent but has not penetrated along the margin in a pulpal direction. Charlie Discoloration has penetrated along the margin in a pulpal direction. Secondary caries Alfa No caries as evidenced by softness, opacity, or etch at the margin of the restoration. Bravo Evidence of caries at margin of the restoration. Postoperative Sensitivity Alfa No postoperative sensltivity. Bravo Postoperativesensitivity present.
RYGE CRITERIA Alpha
FYgure 8. Veneer color match to shade tab using Ryge criteria.
that are not an esthetic concern but may become a functional one. The fractures may have occurred at cementation and became evident over time. The veneers will be monitored for long-term success.
CONCLUSION Within the parameters of this study, Dicor or Dicor Plus veneers fabricated by a competent laboratory technician in combination with the light-activated dual-cure cement are a viable option for the correction of esthetic problems. The restorations are within the shade range of natural teeth and are acceptable to both the patient and the clinician. At 1 year, all of the restorations were clinically acceptable in all categories evaluated (Table 1) with no restoration failures. All of the veneers cemented with the investigational cement appeared to be color stable. Two Dicor veneers have fracture lines in the veneer ceramic. The fracture lines are not an esthetic concern and the two restorations will be monitored over the long term for any future clinical problems.
RYGE CRITERIA Bravo
Figure 10. Veneer interfacial stainfngusing Ryge criterla
Figure 9. Veneer marginal adaptation using Ryge criteria.
JOURNAL OF ESTHETIC DENTISTRY VOLUME 4, SUPPLEMENT 1992
14. Barnes DM, Holston AM, Barnes CA. Castable ceramic veneers: a clinical evaluation. J Dent Res 1991: 70:296. (Abstr 242). 15. Chan D. et al. Microleakage of two esthetic interior porcelain laminate veneers. J Dent Res 1988: 67:311. (Abstr 1585). 16. BarkmeierW,Holston A,Heyde J.Characterized mastique, intraenamel technique. J Indiana Dent Assoc 1984; 63(6):19-23. 17. Barnes DM. Strassler HE, Holston AM. Castable ceramic veneers. J Esthet Dent 1989:1:86-92. 18. Vryonis D. Geller W, KwiatkowsM SJ. The Willy's glass crown: a new solution in the dark and shadowed zones of estheticporcelainrestorations. QuintessenceDentTechnol 1987;1:233-242. 19. Latta MA. The continuing ceramic evolution: Dicor Plus and Dicorcastableceramic.Esthet Dent Update 1990;1:2630. 20. Calamia J,Simonsen R. Effect of coupling agents of bond strength of etched porcelain. J Dent Res 1984: 63:179. (Abstr 79). 21. Barkmeier W. Shaffer S,Gwinrett A. Effects of 15 vs. 60 second enamel acid etch conditioning on adhesion and morphology. Oper Dent 1986;1l(3):111-1 16. 22. Moon PC, Duling D. Curing procedure and bonding agent effect on porcelain veneer microleakage. J Dent Res 1991; 71:209. (Abstr 832). 23. Lynch E.Tay W, Auger D. Effects of some finishing techniques on cervical margins of porcelain laminates. J Dent Res 1987; 66:895. (Abstr). 24. Goetiner D. Sonnenberg E. Maintenance of laminate veneers. Clin Prevent Dent 1982; 4(1):9-12.
REFERENCES 1. Christensen GJ.Aveneering of teeth: state of the art. Dent C h North Am 1985: 29:373-39 1. 2. Coming develops new ceramic material. Am Ceram Soc Bull 1957; 36:279-280. 3. Grossman D. Cast glass ceramics. Dent Clin North Am 1985: 29:725-739. 4. Adair PJ, Hoekstra KE. Fit evaluation of a castable ceramics. J Dent Res 1982; 61:345. (Abstr 1500). 5. Dicor Research Report. Strength of dicor castable ceramic material. Dentsply International Inc 1985: I(2):1-2. 6. CalamiaJ.VaidyanathanS, CalamiaS, HamburgM. Shear bond strength between acid-etched Dicorm and composite resin. J Dent Res 1986; 65:828. (Abstr925). 7. Bennett R. Bailey L. Bonding to dicor laminate veneer. J Dent Res 1986; 65:314. (Abstr 1309). 8. Savitt E. SocranskyS, MelcerA, MalamentK, Blackman H. Effects on colonization of microbiota by cast ceramics crowns compared with natural teeth. Int J Periodont Restor Dent 1987: 7:23-33. 9. Mueninghoff L. ONeal S. Ramus D. Six months evaluation of clinical esthetic veneers. J Dent Res 1988;67:305.(Abstr 1542). 10. Dicor Research Report. Color stabmty of Dicorm castable ceramic material. Dentsply International Inc 1985; I(1): 1-2. 11. PollackB. Blitzer M. Discolorationincompositeand microfiu resins. Am Dent 1984; March-April:130-133. 12. Itachiya Y, Hosoda H, Fusayama T. Relation of finish to discoloration of composite resins. J Prosthet Dent 1984: 52(6):8-14. 13. Ronk S. Dental lamination: clinical problems and solutions. J Am Dent Assoc 1982:104:844
Bonding Ni-Cr Alloy to Tooth Structure with Adhesive Resin Cements Bapanaiah Penugonda, B.D.S., M.S.," Warren Scherer, D.D.S.,t Harmon Cooper, D.D.S.," Noelle Koko1etsos)and Vladik Koifman
This study was to determine the shear bond strengths of Ni-Cr alloyto Ni-Cr alloy (Group I), Ni-Cr alloy to enamel (Group11). and Ni-Cr alloy to dentin (Group 111)using Imperva Dual, DC Metabond, All-Bond, Geristore, and Panavia. All bonded specimens were thermocycled 2000 x (5"C-55"C) after 24 hours and subjected to shear bond testing on a Universal Instron Testing Machine. In all groups of the study, Imperva Dual and CB Metabond had significantly (p c .05)higher bond values than Panavia.