Improving the Physical–Mechanical Property of Dental Composites by Grafting Methacrylate-Polyhedral Oligomeric Silsesquioxane onto a Filler Surface

Endowing dental composites with excellent interfacial bonding through filler surface modification is pivotal to improve the physical-mechanical property and prolong the life of composite fillings. In this study, methacrylate-polyhedral oligomeric silsesquioxane (MA-POSS) acts as a "molecular bridge" between the commonly used SiO₂ particles and the methacrylate-based resin matrix via a thiol-ene click reaction to construct MA-POSS/SiO₂ (p-SiO₂) hybrid particles. Synthesized p-SiO₂ exhibited the roughest surface morphology and had more polymerizable groups, in comparison with SiO₂ and silanized SiO₂. Furthermore, the p-SiO₂ particles were used as a reinforcement to fabricate bisphenol A glycerolate dimethacrylate/tri(ethyleneglycol) dimethacrylate-based dental composites, where the SiO₂- and silanized SiO₂-filled composites served as the control groups, and the filler loading was fixed at 65 wt %. Results of the mechanical properties indicated that the hybrid p-SiO₂ particles significantly improved the flexural strength, flexural modulus, compressive strength, and work of fracture of dental composites, giving improvements of 251.2, 17.89, 122.3, and 1094%, respectively, over the SiO₂-filled composites due to the strong interfacial interaction between the resin matrix and p-SiO₂. Additionally, this optimal p-SiO₂-loaded composite also presented better polymerization shrinkage, acceptable degree of conversion, curing depth, and cell viability. Grafting of MA-POSS onto a filler surface is a promising filler surface modification to improve the resin matrix/filler interfacial interaction, leading to the enhanced overall performance of composites.