Long-term optical stability and surface gloss of CAD/CAM restorative materials under simulated mechanical aging

The long-term optical performance of CAD/CAM restorative materials is a critical determinant of clinical esthetics. Daily mechanical challenges, such as toothbrushing, may progressively alter surface characteristics; however, the long-term optical behavior of contemporary CAD/CAM materials with different compositions remains insufficiently clarified. Therefore, this study investigated the color stability and surface gloss of different CAD/CAM restorative materials under simulated long-term mechanical aging.

Forty-eight disc-shaped specimens (12 × 14 × 2 mm; n = 12 per group) were fabricated from four CAD/CAM restorative materials: feldspathic ceramic (Vita Mark II), zirconia-reinforced lithium silicate (Vita Suprinity), polymer-infiltrated ceramic (Vita Enamic), and resin-based composite (Brilliant Crios). Specimens were finished according to the manufacturers' recommendations. Simulated mechanical aging was performed using a toothbrushing simulator under a 2 N load at 1.25 Hz, corresponding to 1, 3, and 5 years of clinical use. Color change was calculated using the CIEDE2000 formula (ΔE₀₀), and surface gloss was measured with a glossmeter. Data were analyzed using one-way and repeated-measures ANOVA (α = 0.05).

All materials showed statistically significant changes in color and surface gloss after simulated mechanical aging (p < 0.001). Feldspathic ceramic exhibited the lowest ΔE₀₀ values (0.531 after 5 years) and the highest gloss retention (62.68 GU after 5 years), whereas polymer-infiltrated ceramic and resin-based CAD/CAM materials demonstrated greater color change and gloss reduction over time. Zirconia-reinforced lithium silicate showed higher early optical changes followed by relative stabilization. Despite significant inter-material differences, all ΔE₀₀ values remained within clinically acceptable thresholds.

The long-term optical stability of CAD/CAM restorative materials is strongly influenced by material composition. Hybrid and resin-based CAD/CAM materials are more susceptible to brushing-induced surface deterioration and gloss reduction, underscoring the importance of appropriate material selection and surface maintenance for long-term esthetic performance.