Methacryloxypropyl-polyhedral oligomeric silsesquioxane (MAP-POSS) was photopolymerized with the tri- or tetra-functional thiol monomer in different stoichiometry. A novel inorganic–organic methacrylate hybrid material with highly cross-linked network and high performance was synthesized by UV-initiated thiol–ene click chemistry. SEM–EDAX images and XRD diffractograms showed that no agglomeration of MAP-POSS was observed, indicating MAP-POSS dispersed uniformly in the hybrid materials. Real-time FTIR was employed to monitor the conversion of thiol and methacrylate as a function of irradiation time, and the results revealed that highly thiolated monomer could promote the conversion of methacrylate effectively because of stronger chain propagation capability. The TGA indicated that the hybrid materials had high thermal stability of which the onset decomposition temperature rose to 350 °C, approximately 50 °C higher than that of the traditional UV-cured epoxy acrylate/triethylene glycol dimethacrylate (EA/TEGDMA, 70:30 w/w) resin. The highest glass transition temperature ( T g ) of the hybrid materials was 76.2 °C. Compared with traditional EA/TEGDMA resins, the novel hybrid materials consisted of MAP-POSS had fast curing rate, high mechanical properties and thermal stability which made the wider practical applications of UV-cured hybrid materials feasible.
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.
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