Evaluation the Color Stability and Masking Ability of Darkened Teeth Treated With Two Kinds of CAD/CAD Veneer after Thermocycling

Abstract

Objectives: Evaluate color stability and masking ability of darkened substrate restored with two kinds of CAD/CAM veneer materials and the underlying light curing cement (light or neutral) after 1,000,000 thermomechanical cycles. And as a complementary analysis, the residual compression strength of the specimens that survived the thermocycles was carried out. Materials and methods: 60 indirect veneers (IPS e.max CAD and VITA Enamic) with 0.8 mm were prepared using the milling method and cemented on central incisors replicates, non-darkened (A2) or darkened (C4) with light-curing cement: neutral (N) or light (L) (n=10). Spectrophotometer measurements were performed 48h and 72h after cementation and after thermomechanical cycles (250,000; 500,000; 750,000 and 1,000,000). Color differences were evaluated by CIEDE2000 system (ΔE00). The perceptibility threshold was set at ΔE00 = 1.28 and clinical acceptability threshold was set at ΔE00 = 2.24. For the survived samples, compression test was performed as a complementary analysis after specimen ageing. Fractographic analysis was employed to observe fracture patterns. Data were analyzed by two-way ANOVA followed by post hoc Tukey test for color test and compression test by Kolmogorov-Smirnov, Shapiro-Wilk and Tukey test (5%). Results: independent the material and light curing cement used, they were capable to mask the darkened substrate and showed color stability over time, presenting ΔE00 < 0.7. After thermomechanical cycles, lithium disilicate ceramic presented higher residual compression strength and at fractographic analysis demonstrated brittle behavior. Polymer-infiltrated ceramic network presented a plastic deformation and chipping on the veneers’ edges. Conclusion: After 1,000,000 thermomechanical cycles, lithium disilicate ceramic and the polymer-infiltrated ceramic network veneers, processed by CAD/CAM with 0.8 mm and the underlying light curing cement presented color stability and could mask the darkened substrate over time.