Objectives: This study aimed to assess the impact of staining and bleaching procedures on the color alteration of hybrid nanoceramic and zirconia-reinforced lithium disilicate CAD-CAM materials. Materials and Methods: A total of 64 samples (12×14×1.5 mm³) were prepared from A2 shade hybrid ceramic (Cerasmart) and zirconia-reinforced lithium silicate (Celtra Duo) CAD-CAM blocks. After immersion in coffee solution for seven days, each material group was split into two subgroups, then subjected to home or in-office bleaching protocols (n=16). Color measurements were taken at baseline, after coffee staining, and after bleaching, and recorded as L, a, b values. Color differences were calculated as ΔE. Data were analyzed using Kolmogorov-Smirnov and three-way repeated measures ANOVA. Pairwise comparisons between groups were performed using the Bonferroni test. Results: After staining, Cerasmart demonstrated significantly greater discoloration than Celtra Duo (p<0.001). Material differences significantly affected the color change values in terms of staining and bleaching processes. The interactions of time factor with both material and bleaching agent were statistically significant. Conclusions: Hybrid ceramics are more prone to discoloration than lithium silicates. Both home and office bleaching agents are effective in reversing discoloration, with no significant clinical difference between the two methods in achieving initial color values.

Keywords: Bleaching, CAD-CAM, ceramic, color stability, staining.