Effectiveness of Periodic Repolishing on the Surface and Mechanical Properties of Resin‐Based CAD / CAM Materials After Different Cycles of Combined Simulated Toothbrushing and Mechanical Cycling

Objective This study aimed to evaluate the effectiveness of periodic repolishing on the surface and mechanical properties of resin‐based CAD/CAM materials subjected to combined mechanical cycling and simulated toothbrushing, with or without periodic repolishing. Methods Two resin‐based CAD/CAM materials were investigated (Tetric CAD [TC] and Shofu HC [SH]). Groups ( n = 12) were assigned according to the evaluation period and repolishing (RPL) condition. The aging protocol comprised simulated toothbrushing (ST—200 g load, 250 cycles/min) combined with mechanical cycling (MC—50 N load, 1.67 Hz frequency) performed in aging intervals (AI—2.4 × 10 5 MC + 10,000 ST), totaling two periods (5 × AI and 10 × AI). Periodic repolishing was performed using a clinical polishing system (OptraGloss, Diamond High‐Gloss polisher [HP]). Surface roughness (Ra), Vickers microhardness (VH), flexural strength (FS), and elastic modulus (EM) were quantitatively evaluated, while SEM and AFM analyses were performed qualitatively. Data normality and homogeneity were verified, followed by two‐way ANOVA and Tukey's post hoc test ( α = 0.05). Results Aging significantly increased surface roughness and reduced microhardness in both resin‐based CAD/CAM materials ( p < 0.05). Periodically repolished groups (T 1RPL and T 2RPL ) showed higher VH and lower Ra values ( p < 0.05) than their non‐repolished counterparts (T 1 and T 2 ). No significant differences in FS or EM were observed after aging ( p = 0.664 and 0.185, respectively). Conclusion Aging significantly affected the surface roughness and microhardness of both materials. Periodic repolishing proved to be an effective strategy for minimizing the effects of aging, thereby reducing surface roughness and preserving microhardness. Clinical Significance Intraoral repolishing at yearly recall intervals may help control surface degradation, maintain smoother surfaces, and preserve microhardness over time, particularly for indirect restorations fabricated from resin‐based CAD/CAM materials.