Impact of Mechanical and Thermal Aging on the Surface Integrity and Optical Stability of 4Y and 5Y High-translucency Zirconia: A Comparative Study

Objectives: To evaluate the surface roughness and color change of different highly translucent zirconia with or without glaze after toothbrushing simulation and thermocycling. Methods: Forty squared-shaped specimens (3 × 3 mm and 2 mm thick) were milled from two different highly translucent zirconia CAD-CAM blocks ( n = 20): Ceramill Zolid FX Multilayer 71L A1 and Ceramill Zolid HT+ Preshades 71L A1 (AmannGirrbach). Half of the specimens of each zirconia ( n = 10) were stained and glazed (IPS Ivocolor, Ivoclar Vivadent). The surface roughness, confocal microscopy images, and color parameters were obtained at baseline and after aging (48,000 cycles in a toothbrushing simulator followed by 10,000 thermocycles between 5°C and 55°C). The data obtained before and after aging were statistically compared at a significance level of α = 0.05. Results: For both types of zirconia, the surface roughness was found significantly higher for glazed specimens at baseline and after aging ( p < .05); however, the surface roughness of Preshades zirconia significantly decreased after aging for both specimens with (ΔRa: −0.15) or without glaze (ΔRa: −0.13) ( p < .05). Although glazed specimens presented higher lightness after aging, the color change of Preshades specimens was significantly higher than Multilayer specimens ( p < .05). With the exception of glazed Multilayer zirconia, the color change of all specimens was considered clinically perceptible (Δ E ab > 1.2; Δ E 00 > 0.8); moreover, except for Multilayer zirconia with or without glaze, Preshades zirconia exhibited a color change deemed clinically unacceptable (Δ E ab > 2.6; Δ E 00 > 1.8), regardless of the glazing. Conclusion: Both highly translucent zirconia covered by a glaze layer became rougher and showed greater color change after brushing and thermal cycling.