Synergistic modification with silanized MgO nanoparticles and MAP-POSS enhances mechanical performance and antibacterial activity of dental composite resins.

This study developed a dental composite resin incorporating KH-570-modified magnesium oxide nanoparticles (MgONPs) and methacryloxypropyl polyhedral oligomeric silsesquioxane (MAP-POSS), and evaluated its microstructure, physicochemical properties, antibacterial activity, and in vitro cytocompatibility. MgONPs were surface-modified with 3-(methacryloyloxy)propyltrimethoxysilane (KH-570), and composite resin specimens containing 2 wt% modified MgONPs with gradient additions of MAP-POSS were prepared, using a commercial composite resin as the control. Filler structure and modification were characterized by XRD and FTIR, and the composite resins were analyzed by SEM and FTIR. Depth of cure, Vickers hardness, water sorption, solubility, compressive strength, and flexural strength were measured. Antibacterial activity was evaluated against planktonic Streptococcus mutans (S. mutans) using the film contact method, and cytotoxicity was assessed using the CCK-8 assay with L-929 fibroblasts. Among the tested formulations, the specimen containing 4 wt% MAP-POSS and 2 wt% modified MgONPs exhibited the densest microstructure, the highest degree of conversion (83.03%), the greatest depth of cure and mechanical properties, a moderate reduction in viable planktonic S. mutans (R = 1.16), and no obvious cytotoxic response under the tested conditions. These results indicate that the combination of MAP-POSS and silane-modified MgONPs may be a feasible strategy for achieving balanced mechanical reinforcement and antibacterial functionality in dental composite resins.