Cement opacity and color as influencing factors on the final shade of metal-free ceramic restorations

Objective: To investigate the influence of opacity and color of luting cements on the final shade of metal-free restorations. Materials and Methods: Five resin cement colors in combination with four different thicknesses of CAD/CAM ceramic materials were tested, and a composite substrate was used as dentin color reference (n = 3). Specimen color was measured with a spectrophotometer equipped with an integrating sphere before and after cementation (CIELAB). Cement and ceramic color and opacity (TP) were assessed by measuring the tested ceramic thickness as a 1-mm thick disk for each of the cement shades. The differences in color were evaluated (ΔE00). Data were statistically analyzed by a Two-Way ANOVA followed by the Tukey Test for post-hoc comparison (P <.05) and multiple comparison Pearson's test (P <.05); the acceptability and perceptibility threshold were evaluated. Results: Statistically significant influence was found for factors ceramic thickness and cement shade (P <.001). Perceptible and unacceptable color changes were induced on the final restoration by resin cements (ranging from ΔE00 = 0.69 ± 0.54 to ΔE00 = 5.53 ± 0.46), the correlation between factors became strong (r2 > 0.6) in case of mismatch between color and translucency of cement and ceramic. Only the clear shade in combination with the thickest ceramic, resulted in an imperceptible color change (ΔE00 = 0.69 ± 0.54). Conclusions: The final shade of ceramic restorations can be influenced by resin cements; the magnitude of influence is related to the cement optical properties. Clinical Significance: In order to influence the final shade of a ceramic restoration, a cement more opaque than the restorative material should be used. Conversely, in the case of a fitting shade of the restoration, a cement more translucent than the restoration should be used to avoid undesired changes.