Effect of Pre-Colored Zirconia Copings on the Final Color of Zirconia Veneered Restorations: An In vitro Study

Abstract

Background: This study aimed to investigate the effect of different zirconia coping shades on the color and translucency of zirconia-based restorations. Materials and Methods: Zirconia core plates were fabricated from the non-shaded and pre-shaded translucent zirconia materials and were divided into four groups (n=11) according to their shade: Bleach (B), A2, A3, and A4. Next, they underwent porcelain veneering and glazed. The CIELab color measurements were performed before and after porcelain veneering by a colorimeter against white and black backgrounds. Color difference (∆E) between the groups  and translucency parameter (TP) were calculated. ∆E values were compared with perceptibility (∆E=2.6) and acceptability (∆E=5.5) thresholds. Data were analyzed by paired t-test, one-way analysis of variance, and Tukey’s Honest Significant Difference post hoc tests (P < 0.05).  Results: The TP and ∆E of the samples significantly decreased in all groups after porcelain veneering compared with baseline (P<0.001). Against a black background, the ∆E of all groups was below the perceptible threshold after porcelain application (P<0.001). Against a white background, ∆E of all groups decreased to a level lower than the perceptible threshold after porcelain veneering except for groups B-A3 (∆E=3.02±0.73) and B-A4 (∆E=4.10±0.70), in which ∆E was between the perceptible and acceptable thresholds (P<0.001). Conclusions: Porcelain veneering reduces ∆E between two samples more efficiently than pre-colored zirconia copings, especially against a dark background.