A novel antibacterial dental resin composite material with quaternary ammonium salt modified mesoporous silica nanoparticles - an in vitro and in vivo animal study.

Secondary caries remains a leading cause of failure in resin composite restorations. To address the compromised mechanical properties and potential biosafety concerns associated with conventional quaternary ammonium salt (QAS) monomers, we developed quaternary ammonium-grafted mesoporous silica nanoparticles (QA-MSN) as antibacterial fillers for dental resin composites. The resulting QA-MSN-modified resin composites (QM-Resins) demonstrated potent and concentration-dependent antibacterial and antibiofilm activity against Streptococcus mutans. Specifically, the composite containing 10 wt% QA-MSN (10QM-Resin) achieved a 99.7% antibacterial rate and markedly suppressed biofilm formation after 48 h. Moreover, after 7 days of culture, the relative proliferation rates of human gingival fibroblasts and human dental pulp stem cells were 99.8% and 99.5%, respectively, indicating excellent cytocompatibility. Owing to the mechanical interlocking afforded by the mesoporous structure, QA-MSN incorporation increased the elastic modulus of the composites without adversely affecting flexural strength, degree of conversion, water sorption, or solubility. In a rat secondary caries, 10QM-Resin significantly reduced both Keyes' scores and lesion depth, demonstrating effective inhibition of caries progression. Collectively, these findings indicate that QA-MSNs represent promising antibacterial fillers for developing dental resin composites with enhanced resistance to secondary caries.