Preparation of a highly crosslinked biosafe dental nanocomposite resin with a tetrafunctional methacrylate quaternary ammonium salt monomer

The design of antimicrobial dental nanocomposite resin to prevent secondary dental caries and minimize biosafety problems is an important endeavor with both fundamental and practical implications. In the present work, a novel tetrafunctional methacrylate-based polymerizable quaternary ammonium monomer (TMQA) was synthesized with the aim of using it as an immobilized antibacterial agent in methacrylate dental composites, and its structure was characterized. The antibacterial action of TMQA and polymerized resin specimens against suspected cariogenic bacteria Streptococcus mutans were evaluated. Furthermore, the double bond conversion, contact angle, water sorption, solubility, heterogeneity, and crosslink density of the experimental resins with different concentrations of TMQA were investigated. CCK-8 and real-time cell analyses were used to evaluate the cytotoxicity of the experimental resins. The results showed that TMQA was successfully synthesized and had strong antibacterial properties against Streptococcus mutans. The experimental resins with different concentrations of TMQA had a similar degree of conversion and contact angle to the neat resin. With the addition of 4% TMQA to the resins, water absorption and solubility were reduced while their heterogeneity and crosslink density increased. The cell viability of each experimental group was similar to that of the neat resin group and was higher than that of the commercial adhesive single bond 2 group. Therefore, TMQA can be used to impart antibacterial properties to resins and increase the crosslink density of dental resin composites.