CAD/CAM veneers: effect of material and thickness on color masking, bond strength and marginal fit
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New CAD/CAM materials are becoming more accepted in veneer restoration. The objective is to investigate the margin integrity of CAD/CAM veneer, their color masking over dark backgrounds and shear bond strength (SBS) to resin cements. Materials and Methods: Four types of CAD/CAM materials shaded A2: Lava Ultimate (LU); IPS Empress CAD (IPS); Vita Enamic (VE); and Vitablocs Mark II (VMII) were sectioned into tiles of different thicknesses: 0.3mm, 0.5mm and 0.7mm (n=7). The color (CIE - L*a*b*) of each specimen was measured against grey background, then against each tooth-shaded background: A3, A4, B3 and C2 acrylic (Coldpac, Motloid). Color differences (ΔE) were calculated. Specimens were measured against black then white background to calculate translucency. Two-way ANOVA was used to compare the differences in ΔE among the groups (a=0.05). SBS values of 2mm thick tile specimens of the same CAD/CAM materials to resin cements, RelyX Ultimate and Varilonik Veneer, were measured using Instron Universal Testing Machine. (n=10). Statistical analysis was performed by ANOVA with Tukey-Kramer HSD multiple comparison test (a=0.05). Qualitative evaluation of margin integrity of the veneers milled from the same CAD/CAM materials in three thicknesses 0.3, 0.5 and 0.7mm were observed under the optical microscope. Results: Significant differences in masking capabilities were found among the tested material for all three thicknesses. In comparison of ΔE values of the tested materials over tooth-shaded backgrounds, specimens over shade A3 background showed the highest color masking ability. LU and VE exhibited better color masking than IPS and VMII. IPS showed significantly higher in translucency than the other groups. IPS showed the highest SBS to resin cements and LU showed lowest SBS. Materials cemented with RelyX showed significantly higher SBS values than those with Variolink. CAD/CAM milled LU and VE veneers show smoother margins when compared to IPS and VMII. Conclusion: LU and VE exhibited higher color masking, lower translucency, lower SBS values, and better margin integrity than IPS and VMI.