Physicochemical and Antibacterial Properties of a Mussel-Inspired Chlorinated Monomer Modified Dental Resin Matrix

Introduction and aims Cariogenic biofilms at the resin-dentin interface frequently trigger secondary caries. This study aimed to synthesize a mussel-inspired chlorinated dopamine methacrylamide (Cl-DMA) monomer and evaluate its impact on the physical, antimicrobial, and biological properties of an experimental dental resin. Methods Cl-DMA was integrated into a Bis-GMA/TEGDMA/HEMA matrix at mass ratios of 0, 1, 3, and 5 wt%. The physicochemical properties of Cl-DMA-modified resin matrix were evaluated by contact angle, water sorption, water solubility, degree of conversion, flexural strength, and modulus of elasticity. The release of Cl-DMA monomer from the resin matrix was monitored for 14 days using HPLC. Antimicrobial efficacy against Streptococcus mutans was quantified through CFU counting, CCK-8 assays, inhibition zone tests, scanning electron microscopy observation of biofilms, and fluorescent staining of live/dead bacteria. The in vitro cytotoxicity of the resin extracts was evaluated using L929 mouse fibroblasts via CCK-8 assay and live/dead staining observation. Results Incorporating 1 to 3 wt% Cl-DMA preserved adequate immediate polymerization and mechanical strength, though a significant decline in flexural strength and modulus was observed across all groups after 28-day water ageing. Release kinetics strictly followed Fickian diffusion. The modified resins achieved a >2.5-log 10 reduction in biofilm viability primarily via contact-killing. The 5 wt% group showed impaired polymerization, mechanical properties, and significant cytotoxicity. Conclusion Adding 3 wt% Cl-DMA endows dental resin with robust contact-killing capabilities without compromising immediate physical properties or biosafety. However, 28-day water ageing caused a significant decline in mechanical properties across all groups, indicating that the current unfilled resin formulation requires further optimization for long-term clinical application. Clinical relevance This chlorinated biomimetic monomer shows promise as an antimicrobial component for dental resin formulations; however, further investigation in long-term and in vivo models is required to assess its clinical potential.