In vitro comparison of the surface roughness of three nanohybrid resin composites before and after dry and wet polishing.

Background: Nanohybrid resin composites are widely used in esthetic dentistry, and the choice of an appropriate polishing technique can influence their surface properties. The aim of this study was to compare, in vitro, the surface roughness of three nanohybrid resin composites before and after dry and wet polishing. Material and Methods: This in vitro longitudinal experimental study included 60 composite resin discs, evenly distributed into three groups (n = 20): Filtek Z250XT, Opallis, and Tetric N-Ceram. Each group was further divided into two equal subgroups (n = 10) for the application of dry and wet polishing techniques. Surface roughness was measured using a digital profilometer before and after polishing. Independent and paired Student's t-tests were used for statistical analysis, with a significance level set at p < 0.05. Results: Prior to polishing, no significant differences in average surface roughness (Ra) were found among the resin groups, indicating adequate standardization: Filtek Z250XT (p = 0.899), Opallis (p = 0.585), and Tetric N-Ceram (p = 0.721). Following dry or wet polishing, no significant intragroup differences were observed: Filtek Z250XT (p = 0.066), Opallis (p = 0.124), and Tetric N-Ceram (p = 0.584). When comparing pre- and post-treatment values, Filtek Z250XT showed a significant reduction only with wet polishing (p = 0.003). In contrast, both Opallis and Tetric N-Ceram exhibited a significant decrease in roughness with both polishing methods: dry (p = 0.044 and p = 0.001, respectively) and wet (p < 0.001 for both). Conclusions: Both dry and wet polishing were effective in reducing the surface roughness of Opallis and Tetric N-Ceram resin composites, whereas in Filtek Z250XT, a significant reduction was observed only with wet polishing. These findings suggest that the effectiveness of the polishing procedure may vary depending on the type of resin composite, which should be considered when selecting clinical finishing and polishing protocols to optimize the surface properties of restorative materials. Key words:Comparative study, Composite Resins, Dental materials, Dental polishing, Surface properties, surface roughness.