Surface texture and wear characteristics of micro-hybrid and nano-hybrid resin composites under simulated frictional conditions.

The goal of work was to evaluate the surface texture and wear behaviour of two resin-based composites – AP-X (micro-hybrid) and FSE (nano-hybrid), under two frictional conditions. Specimens were subjected to simulated occlusal wear using the ACTA wear machine, following two-body wear (full contact) and three-body wear (slurry-lubricated) protocols. Surface texture was assessed before and after wear using 3D profilometry and SEM. Roughness parameters and wear rate were measured. SEM micrographs provided insights into wear mechanisms. Initial surface roughness of FSE was higher than AP-X due to nanocluster morphology (Ra: 0.965–1.050 μm vs. 0.470–0.489 μm; Sq: 1.25–1.32 μm vs. 0.554–0.667 μm ). Two-body wear caused significant degradation in FSE, including nanocluster plucking and matrix cracking, whereas AP-X showed more stable wear resistance. Under three-body wear, FSE demonstrated a polishing effect (Ra reduced to 0.564 μm; Sq reduced to 0.766 μm), while AP-X experienced increased surface roughness (Ra increased to 0.966 μm; Sq increased to 0.869 μm) due to macro-filler exposure. Wear analysis confirmed higher material loss under three-body friction conditions. FSE exhibited better performance under slurry-lubricated conditions but was more susceptible to fatigue-driven degradation in full contact. Conversely, AP-X demonstrated superior stability under two-body wear, making it more suitable for bruxers.