Effects of Substructure Color and Restoration Thickness on the Final Color of Ultra-Translucent Zirconia Ceramics

This in vitro study aimed to evaluate the effects of substructure color and restoration thickness on the final color of shade-gradient ultra-translucent zirconia ceramics.

A total of 180 flat-shaped ultra-translucent zirconia specimens (5Y-PSZ) with thicknesses of 0.4, 0.6, and 0.8 mm (n = 60) were fabricated and cemented onto composite substructures in six colors (A1, A2, B1, B2, C2, D2). Color parameters were measured before and after cementation, and color differences (ΔE ₀₀) were calculated using the CIEDE2000 formula. The data were evaluated using the two-way repeated measures of ANOVA, Kruskal-Wallis, Tukey HSD, and Bonferroni tests (α = 0.05).

Substructure color and restoration thickness had significant effects on ΔE ₀₀ (p < 0.001) after cementation, with values exceeding the acceptability threshold (1.8) in all groups. Before and after cementation, A2 remained below the acceptability threshold relative to target color A1 and B2 achieved acceptable color matching with increased thickness.

Restoration thickness and substructure color significantly influenced the final color of shade-gradient zirconia ceramics. A2 provided better color matching, while B2 required a minimum thickness of 0.8 mm for acceptable results.

Increased zirconia thickness enhances masking of darker substructures. Additionally, the influence of the substructure color must be carefully considered, particularly in thinner ultra-translucent zirconia ceramics, to ensure predictable, harmonious color matching.