Evaluation of Surface Roughness of Multilayered Monolithic Zirconia Following Chairside Adjustment with 3 Different Polishing Systems Sterilized for Multiple Cycles: An In Vitro Study

Background: Chairside grinding, finishing, and polishing are essential for smoothing multilayered monolithic zirconia (MMLZ) restorations. Due to rubber matrix hardening, repeated sterilization of finishing and polishing instruments reduces their abrasive effectiveness. This study aimed to evaluate the effects of sterilization cycles on the effectiveness of 3 commercial polishing kits on the surface roughness of MMLZ crown restorations. Material/Methods: One hundred milled, disc-shaped zirconia specimens (10 mm diameter, 3 mm thickness) were divided into 3 groups (n=30) based on the polishing kit used [EVE Diacera, SS White, Ultradent Jiffy]. Each group was further subdivided based on 1, 5, or 10 flash sterilization cycles (n=10). Profilometers measured average surface roughness while objective qualitative analysis was performed by scanning electron microscopy. A one-way ANOVA (Kruskal-Wallis) rank test and a post-hoc Dunn test with Bonferroni correction were used to determine the significance of median values and mean rank scores. The significance threshold for probability 'P' value was set at P <= 0.05. Results: After 5 autoclaving cycles, the EVE Diacera group had a statistically significant increase in surface roughness (P=0.0009), which decreased somewhat after 10 cycles. The Ultradent Jiffy reduced surface roughness after repeated autoclaving, but SS White did not. Surface roughness did not change across groups after multiple autoclaving cycles, according to post-hoc analysis. Conclusions: MMLZ surface roughness produced by all 3 polishing systems was clinically acceptable after 10 flash sterilization cycles. Ten flash sterilization cycles did not affect the efficiency of any of the polishing systems to produce a smooth surface on the MMLZ specimens.