Polymer Composite Design Strategies for Antibacterial Resin-Based Dental Restorative Composites: Mechanisms,...

Dental resin composites are widely used for direct restorations, yet their longevity remains limited by biofilm accumulation and secondary caries at the tooth-restoration interface. Unlike previous reviews that have primarily organized antibacterial dental materials according to antimicrobial agents or mechanisms, this narrative review evaluates antibacterial resin composites from a polymer-composite design perspective, integrating molecular architecture, network immobilization, filler-matrix interactions, polymerization, and aging. Leachable agents such as chlorhexidine provide early antibacterial effects but are constrained by reservoir depletion, water sorption, and release-related material changes. In contrast, covalently immobilized quaternary ammonium monomers provide sustained surface-associated activity without continuous release, although their performance depends on molecular structure, concentration, degree of conversion, and network properties. Antibacterial nanoparticles and bioactive glass fillers provide composition-dependent ion-mediated, photocatalytic, pH-modulating, and remineralizing effects, while their performance depends strongly on particle characteristics, dispersion, and formulation. Multifunctional systems further combine antibacterial activity with protein repellence, mineral protection, and rechargeable ion release. Overall, the evidence indicates that durable antibacterial performance cannot be considered independently of polymerization, mechanical integrity, aging stability, and biocompatibility. Future development should therefore prioritize clinically relevant multispecies biofilm models, standardized aging protocols, structure-property analysis, and long-term in vivo and clinical validation.