Smart resin composite with acid-activated antibacterial monomers and calcium phosphate nanoparticles to resist dental caries.

OBJECTIVE: To develop a smart resin composite with acid-activated antibacterial effect and controlled release of calcium (Ca) and phosphate (P) ions to prevent secondary caries.

METHODS: Dodecylmethylaminoethyl methacrylate (DMAEM) and nanoparticles of amorphous calcium phosphate (NACP) were incorporated into resin composite. Mechanical strength, cytotoxicity, Ca/P ion release, and the antibacterial effect in acidic and neutral medium were tested. The antibiofilm effect before and after 30-d microbial aging was investigated. The enamel hardness by enamel-restoration margins was measured under a 7-d biofilm model.

RESULTS: 3% or 4% DMAEM and 20% NACP modified resin composite demonstrated similar flexural strength, elastic modulus and cytotoxicity with the control group (p > 0.05). The Ca/P ion release of DMAEM + NACP groups at pH 4 was over 4-fold greater than that at pH 7. The Streptococcus mutans biofilm activity and acid production of DMAEM + NACP groups in acidic medium was decreased by 95% (p < 0.05), while in neutral medium, the effect was attenuated. The DMAEM+NACP resin composite inhibited the saliva-derived biofilm activity and acid production, and reduced the CFU counts, both before and after aging (p < 0.05). After biofilm demineralization, enamel micro-hardness of DMAEM + NACP groups was twice that of control groups (p < 0.05).

CONCLUSION: The novel DMAEM + NACP resin composite showed persistent acid-activated antibacterial effect and Ca/P ion release, with good mechanical strength and low cytotoxicity. It also preserved the enamel micro-hardness at the restoration margins.

CLINICAL SIGNIFICANCE: The study on the smart multifunctional resin composite provides a promising strategy to inhibit secondary caries.