Comparative evaluation of translucency changes in pre-shaded and externally stained CAD-CAM ceramics after thermocycling aging

Background Matching translucency, in addition to shade, ensures that restorations blend harmoniously with natural teeth by replicating depth, vitality, masking capability, and enduring esthetic longevity. Objective This in vitro study investigated the influence of thermocycling aging on the translucency parameter (TP) of pre-shaded and externally stained CAD-CAM all-ceramic materials. Methods Square-shaped ceramic discs (11 × 11 × 1.5 mm; n = 20 per group) were fabricated from lithium disilicate (LDS-CAD), zirconia-reinforced lithium silicate (ZLS-CAD), and high-translucency monolithic zirconia (MZ-HT). Ten specimens from each group were further processed with the corresponding external stains (IPS e.max CAD Crystall, Celtra universal stains, or Ceramill liquid). Baseline TP values were determined spectrophotometrically from the color difference between white and black backgrounds. Specimens were then subjected to 10,000 thermocycles between 5 °C and 55 °C, after which TP values were remeasured. Data were analyzed using three-way mixed ANOVA and Tukey's HSD test (p < 0.05). Results At baseline, pre-shaded MZ-HT exhibited the highest TP values (20.51 ± 2.17), followed by pre-shaded ZLS-CAD (16.92 ± 0.83) and LDS-CAD (15.07 ± 1.29). External staining led to a marginal reduction in TP across all groups. Three-way mixed ANOVA revealed significant effects of material and coloration technique on TP values. A significant Material × Aging interaction indicated that the effect of thermocycling differed among ceramic materials, with zirconia showing the greatest change following aging. Conclusion Translucency was significantly influenced by ceramic material and coloration technique. The effect of thermocycling aging on TP was material-dependent, with high-translucency zirconia showing the greatest change.