Balancing Antibacterial Activity and Mechanical Performance in Dental Resins Using a Cellulose‐Derived Crosslinker

ABSTRACT Secondary caries driven by biofilm accumulation at restoration surfaces and tooth–restoration interfaces remains a major cause of failure for resin‐based restorations, motivating the development of non‐leaching, contact‐active antibacterial dental resins. However, strengthening antibacterial/anti‐adhesion performance by incorporating functional comonomers often compromises mechanical durability, largely due to reduced effective crosslink density and increased susceptibility to hydrolytic degradation. Here, we address this bioactivity–durability trade‐off by synergistically incorporating a cellulose‐derived methacrylated macromer/crosslinker (ECM) and a fluoride‐containing quaternary ammonium methacrylate antibacterial monomer (DMAHDM‐F) into a dental resin matrix. ECM serves as a multifunctional macromolecular crosslinking element to reinforce network integrity and enhance effective crosslink density, while DMAHDM‐F provides covalently immobilized, non‐leaching antibacterial activity via quaternary ammonium functionality. The optimized formulation (ACDR‐5) combines high flexural strength and modulus with pronounced antibacterial efficacy against Streptococcus mutans . Moreover, ACDR‐5 maintains > 90% viability of human gingival fibroblasts, indicating favorable cytocompatibility. This dual‐functional, network‐reinforced design provides a straightforward strategy to reconcile sustained antibacterial performance with mechanical durability in light‐cured dental resins.