Influence of ceramic translucency, ceramic thickness, and shades of luting resin cement on final color of CAD/CAM lithium disilicate veneers

Purpose. To evaluate the effect of ceramic translucency, ceramic thickness, and cement color on the final optical color of a CAD/CAM lithium disilicate ceramic. Methods. A total of 180 ceramic specimens were prepared into two thicknesses, 0.5 and 1.0 mm, from high translucency (HT), medium translucency (MT), and low translucency (LT) CAD/CAM lithium disilicate ceramics (IPS e.max CAD; Ivoclar Vivadent) in shade A1. Substrates were fabricated from resin composite in shade A3. Two shades of light-cure resin cement, neutral and light plus (Variolink Esthetic LC; Ivoclar Vivadent), were used for cementation, whereas glycerine was used for the control groups. CIE L*a*b* color coordinates for each combination were measured via a spectrophotometer (Ultrascan Pro, Hunter Lab). The data were calculated using the CIEDE2000 (ΔE00) formula to find color differences and analyzed with three-way ANOVA and Bonferroni post-hoc multiple comparison tests (a = 0.05). Additionally, ΔE00 values were evaluated by comparing the perceptibility threshold (PT) and the acceptability threshold (AT) of 0.8 and 1.8, respectively. Results. Three-way ANOVA revealed that ceramic translucency, ceramic thickness, and cement color had statistically significant effects on final colors of the ceramic veneers. Mean ΔE00 values fell within the acceptable range for most groups, except those using 0.5 mm HT ceramics with light plus cement, which was also the highest mean ΔE00 value (1.85 ± 0.14). The lowest mean ΔE00 value was obtained from a group using 1.0 mm LT ceramics with light plus cement (0.35 ± 0.15). Conclusion. Ceramic translucency, ceramic thickness, and cement color influenced the final color of lithium disilicate veneers. In most of the study groups, a decrease in ceramic translucency and an increase in ceramic thickness lessened color differences. A white, opaquer shade cement provided better color modification and brightness enhancement than a highly translucent shade cement.