The Effect of Substrate Shades on the Outcome Color of the Chairside CAD/CAM Restorative Material for Veneer Restorations

The aim of this study was to investigate and compare the translucency and the color differences of several kinds of CAD-CAM materials against different resin backgrounds.A total of 66 specimens measuring (12 × 14 × 0.6 mm ± 0.01 mm) were prepared from eleven CAD/CAM materials (Lava Ultimate HT/LT, Vita SuprinityHT/T, Vita Enamic HT/T,Vita Blocs MarkII, IPS Empress CAD HT/LT, IPS e.max CAD HT/LT). Then composite resin specimens (n=1) were fabricated in 5 shades（A2, A4, B2, C2 and D2）to simulate the normal background dentine shade. A spectrophotometer was used to measure the translucency parameter (TP) and color difference (ΔE00) of the samples. Commission Internationale d’Eclairage (CIE) L*a*b* values of ceramic specimens over the A2 Shade served as the control group for others. Data of the experimentalA4, B2, C2 and D2shades acting as abutment were analyzed and compared to the control shade A2. Color differences values between control and test groups were computed using CIEDE2000 Formula. Among all the materials, VitaEnamic T showed lowest TP values (34.98±0.77), whereas LavaUltimate HT showed highest TP values (51.08±1.35). The color differences of all the materials under the B2 shade background are lower than 2.25, which is clinically acceptable. However, under the A4, B2, C2 and D2 shades background, the color differences of all the materials are far more than 2.25, which indicates the ΔE00 values is affected by the resin background. The results of two-way ANOVA showed that the color differences were influenced by materials, background, as well as the interaction terms of these two variables (p<0.05). The substrate color mainly affects the final color of CAD/CAM veneer. Microstructure of CAD/CAM material also affects its translucency property.