Summary: This study aimed to evaluate the surface roughness of two different light-cured resin-composites (Tetric EvoCeram and Sinfony) when opposed by monolithic zirconia after simulated mastication. After subjecting the materials to in vitro chewing against zirconia using a chewing simulator for 250,000 cycles, a 3D profilometer assessed surface roughness parameters before and after the simulation. Sinfony exhibited significantly greater roughness values compared to Tetric EvoCeram, except for Sa and Sv parameters after chewing. Both materials showed increased roughness after chewing, with Tetric EvoCeram experiencing significant surface damage post-simulation. This research highlights differences in surface roughness between the two resin-composites and their responses to simulated mastication, suggesting Tetric EvoCeram's smoother surface but increased susceptibility to damage compared to Sinfony.