Effect of Thermocycling and Staining Solutions on Translucency Parameter and Color Stability of Ultratranslucent Monolithic Zirconia and Lithium Disilicate Laminate Veneers: An In-Vitro Study

Objective
To evaluate and compare the translucency parameter (TP) and color stability (ΔE₂₀₀₀) of ultratranslucent 5Y-PSZ zirconia and lithium disilicate laminate veneers following standardized thermocycling protocols with simultaneous exposure to coffee and orange juice staining solutions.
Methods
Forty-eight anatomically-correct laminate veneers were fabricated using CAD/CAM technology from ultratranslucent 5Y-PSZ zirconia (Katana UTML) and lithium disilicate (IPS e.max CAD HT) blocks (n=6 per group). Specimens were randomly allocated to four experimental conditions with combined thermocycling (2,500 cycles, 5°C-55°C) and staining protocols. Translucency parameter and color coordinates were measured using spectrophotometry at baseline and post-treatment. Data were analyzed using two-way ANOVA with Bonferroni post-hoc correction (α=0.05).
Results
Both materials demonstrated statistically significant changes in TP and ΔE₂₀₀₀ following aging. Orange juice staining produced significantly greater color changes in lithium disilicate compared to zirconia (5.45±1.76 vs 3.74±0.66, p=0.023). Zirconia exhibited dramatically increased translucency following orange juice exposure (15.54±4.59 vs baseline 5.21±3.45), while lithium disilicate maintained stable translucency across conditions (p=0.196). Two-way ANOVA revealed a highly significant interaction between material type and aging intervention (F=13.867, p<0.001, η²=0.394). All color changes exceeded clinical acceptability thresholds (ΔE₂₀₀₀>1.8).
Conclusions
Both materials experienced clinically significant optical changes following accelerated aging. The highly significant interaction effect demonstrates material-specific responses to aging protocols. Zirconia showed superior color stability under orange juice exposure but exhibited unexpected translucency increases requiring further investigation. These findings support individualized material selection based on patient dietary habits and emphasize comprehensive patient counseling regarding long-term esthetic expectations.