Effects of Substructure Color, Cement Shade, and Aging on the Color Change of Multilayer Zirconia Laminate Veneer Restorations

The purpose of the present study was to evaluate the effects of zirconia material type, substructure color, cement color, and aging (before and after aging) on the color change of laminate veneers (LVs) prepared from different multilayer translucent zirconia ceramics. LV preparation was performed on a phantom tooth, and the preparation was digitized to produce resin abutments in two shades (light: A1/B1; medium: A2/A3) to simulate different tooth colors. LVs were designed using dental design software and fabricated from three multilayer zirconia ceramics (multilayered super-high-translucent 5Y-TZP zirconia, multilayered high-translucent 4Y-TZP zirconia, and multilayered ultra-translucent 5Y-TZP zirconia), resulting in 12 experimental groups (n = 10). They were then cemented with either clear or white resin cement and subsequently subjected to 10,000 cycles of thermal aging. The color parameters were measured at three time points (before cementation, before aging, and after aging), and the color change values (ΔE00) were calculated. The data were statistically analyzed, and the results were compared with the perceptibility threshold (ΔE00 = 0.8) and the clinical acceptability threshold (ΔE00 = 1.8). Four-way ANOVA revealed an interaction among zirconia material, substructure color, cement shade, and measurement time (p = 0.02). Color change values after cementation (ΔE00-1) across all groups showed a statistically significant difference between the white and clear cement groups. Before aging, the color change values observed in the 4Y-TZP (DD Cube One ML)-medium abutment–white cement (ΔE00-1 = 1 ± 0.2) and 5Y-TZP (Katana UTML)-medium abutment–white cement (ΔE00-1 = 1.6 ± 0.7) groups were above the perceptible threshold value but were clinically acceptable (0.8 < ΔE00 < 1.8). The color change values observed after aging (ΔE00-2) across all experimental groups were clinically unacceptable (ΔE00 > 1.8). The color changeof ultra-translucent zirconia LVs was influenced by zirconia material type, cement shade, substructure color, and aging, with the effect of the zirconia material itself being less pronounced. Aging further reduced color stability, resulting in increased ΔE00 values and clinically unacceptable color differences.