Effect of polishing on hybrid CAD/CAM ceramics after gastric acid

Abstract

Objective: To evaluate the effects of polishing systems and simulated gastric acid on the surface roughness and Vickers microhardness of hybrid CAD/CAM ceramics. Material and method: Forty specimens (n=10/group) were prepared from a polymer-infiltrated ceramic network (VITA Enamic) and a resin nanoceramic (Cerasmart). Specimens were polished with either a conventional ceramic polishing system (CPS) or a hybrid-specific polishing system (HSP). Surface roughness (Ra) and Vickers microhardness (VHN) were measured after 24 h and after cumulative immersion in 5% hydrochloric acid (pH 2.0) for 91, 182, and 455 h, cumulative simulated gastric acid exposure periods. Data were analyzed by three-way mixed-design ANOVA with repeated measures and Tukey’s post hoc test (α=0.05). Result: Significant interactions among material, polishing system, and evaluation period were found for both outcomes (p<0.05). HSP reduced the roughness of VITA Enamic compared with CPS at all periods, whereas no consistent improvement was observed for Cerasmart. VITA Enamic showed higher microhardness than Cerasmart regardless of the polishing method. Simulated gastric acid reduced microhardness over time in both materials, while roughness depended on the interaction between material and polishing protocol. Conclusion: The hybrid-specific polishing system resulted in lower surface roughness for the polymer-infiltrated ceramic network, whereas no consistent benefit was observed for the resin nanoceramic. Simulated gastric acid exposure was associated with reductions in microhardness at specific evaluation periods in both materials. These findings are limited to the surface properties evaluated under the experimental conditions.