The Effect of Simulated Chewing on the Surface Roughness of Direct and Indirect Resin-Composites Opposed by Zirconia: An In Vitro Study

Abstract

Purpose. To assess the surface roughness of two different light-cured resin-composites when opposed by monolithic zirconia after simulated mastication. Materials and Methods. Materials included a direct restorative nanohybrid ( $n=10$ ) and an indirect microhybrid ( $n=10$ ) resin-composite (Tetric EvoCeram and Sinfony, respectively). The antagonist material was 3 mol% yttria-stabilized tetragonal zirconia polycrystalline ceramic. Each material was subjected to in vitro chewing against zirconia using a chewing simulator for 250,000 cycles. A 3D profilometer was used to assess the surface roughness parameters of each resin-composite before and after the simulated chewing. Independent $t$ -test and paired sample $t$ -test were performed to compare roughness values for both materials and to compare baseline and after chewing simulation values ( $p=0.05$ ). Results. Sinfony showed significantly greater roughness values compared to Tetric EvoCeram ( $p\le 0.025$ ) before and after simulated chewing, except for Sa and Sv parameters after simulated chewing where the difference between the two materials was insignificant ( $p=0.06\text{and}0.89$ , respectively). Surface roughness increased for both materials after simulated chewing compared to baseline values, but the difference was insignificant ( $p\ge 0.065$ ). However, $Sa$ ( $p=0.04$ ) and $Sv$ ( $p=0.012$ ) for Tetric EvoCeram were significantly higher after compared to before chewing simulation. Conclusion. Tetric EvoCeram had a smoother surface than Sinfony before and after simulated chewing. Surface roughness for both materials was higher after simulated chewing compared to baseline values which represent surface damage that was significant for Tetric EvoCeram while Sinfony showed better resistance.