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.