Influence of thickness and background on the color changes of CAD/CAM dental ceramic restorative materials

This study aimed to compare the effect of thickness and background on the color changes of CAD/CAM materials (zirconia-reinforced lithium silicate (Suprinity), lithium disilicate (IPS E-max CAD), and hybrid ceramic (Enamic)). Twelve specimens for each thickness (0.4 mm, 0.5 mm, 1 mm, 1.5 mm, and 2 mm) were obtained by sectioning three CAD/CAM materials. A spectrophotometer was used to measure the color change of the specimens against different backgrounds (A2 enamel, A4 dentin, gray, and metal) using the CIELab color space system. Analysis of variance, sample t-test, and posthoc multiple comparison tests were used to evaluate and compare the color changes for different material types, thicknesses, and background colors, with a significance level of P ≤ 0.05. The result demonstrated that material type, the thickness of the material, and the color of the background had a significant effect on ΔE (P = 0.000). Regardless of the material thickness, Suprinity had the highest mean ΔE values (5.4 1.9), and E-max had the lowest mean ΔE values (1.1 0.6). At 2 mm thickness, Enamic presented the lowest ∆E values (0.5 0.5) against the A2 background. The 0.5 and 1 mm specimens corresponded to the highest ΔE values, whereas the 1.5 and 2 mm thickness specimens predominantly gave the lowest ΔE values. All the independent factors, including the type and thickness of the material, and color of the background, contributed significantly to ΔE of the tested materials (P ≤ 0.05). The study confirms the high masking ability of the lithium disilicate (E-max) material. In clinical situations where the color of the core needs to be masked, it is recommended to use lithium disilicate (E-max).