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cosmetic dentistry - beauty & science

I 11 special topic _ porcelain laminate veneers I cosmeticdentistry 2_2012 glazing effect (Figs. 24a & b). If you want to make interim veneers using a direct method, I recom- mend placing the silicone matrix over the ther- moplastic sheet during fabrication in the mouth because the thickness of an interim veneer is too thin to control with a thermoplastic sheet only (Figs. 25a–d). _Material selection Once the dental laboratory receives the final impression, two stone casts will be made—a mas- ter cast and a solid cast. The master cast will be used for individual die fabrication, wax-ups, in- ternal fit, margin fit and occlusal contact checks. Thesolidcastwillbeusedmainlyforproximalcon- tact check and labial surface contour, which needs to be harmonised with the soft tissue (Figs. 27a & b). In addition, for diagnostic casts, a duplicate cast of the diagnostic wax-up and intra-oral pho- tographs for shade selection must be shipped to the laboratory for the final veneer fabrication (Figs. 28a & b). Pressable ceramic material is recommended be- causeofitsenhancedaestheticpropertyinlayering technique, and for its strength and stability with resin bonding cements. When you select a lost- wax method, a laboratory technician creates a full- contour wax-up on the master cast, guided by the duplicate diagnostic cast and the doctor’s instruc- tions (Fig. 29). After the initial pressing, a cut-back is made on the incisal area of the ceramic veneers in order to create room for additional porcelain to be added. This layering technique is used to create lifelike translucencyintheincisalthirdoftheveneers(Figs. 30a–c). Forexternalstainingandglazing,usethestump- shade resin dies to create an accurate matching of shade(Figs.31a&b).Theeffectofmultiplefiringson the marginal integrity of the pressable veneers is minimal.3 Final veneers are evaluated on both the master cast and the solid cast (Figs. 32a & b). Occlusal con- tacts during eccentric movement are then eval- uated and adjusted (Fig. 33). The intaglio (inner) surfaces of the veneers need to be treated with hydrofluoric acid in the laboratory. _Cementation If thickness and opacity of veneers are impor- tant factors, I recommend using dual-cure resin cements for pressable ceramic veneers. However, light-cure resin cements also have some advan- tages, such as extended working time and colour stability due to the fact there is no amine degra- dation. First, after receiving the veneers from the lab- oratory, you should evaluate facial veneer surfaces on the three different planes: incisal third, middle third and cervical third (Figs. 34a–c), as you did during the diagnostic phase (Figs. 3a–c). You can easily verify whether the veneer surfaces have been built to a harmonised contour with adjacent teeth. Look for over-contouring. Evaluate the form and thicknesswithasiliconematrixandadigitalcalliper (Figs. 35a & b). Second, on the try-in date, remove the interim veneers gently and try in the veneers with a recom- mended try-in resin paste in this order: central in- cisor, lateral incisor and canine. Clinically evaluate the shade, form and margin (Figs. 36a–c), and then Fig. 39a Fig. 39c Fig. 37a Fig. 37b Fig. 37c Fig. 38 Fig. 39b