Evaluation of the effects of combined application of dimethylaminohexadecyl methacrylate and MDP on dentin bonding and antimicrobial properties

This study aimed to evaluate the effects of the combined application of dimethylaminohexadecyl methacrylate (DMAHDM) and 10-methacryloyloxydecyl dihydrogen phosphate (MDP) on dentin bonding and its antimicrobial properties. DMAHDM was incorporated into the adhesives at 5% by mass, where two commercial adhesives were used: (1) MDP-free adhesive (single bond 2); (2) MDP-containing adhesive (single bond universal, SBU). The microtensile bond strength (μTBS) and nanoleakage were analyzed on the combination. The effects of DMAHDM on the interaction between MDP and hydroxyapatite and the degree of conversion were assessed by Fourier transform infrared spectroscopy (FTIR). Antimicrobial properties were examined by live/dead staining assay, colony-forming units (CFU), and metabolic activity, and cytotoxicity was measured using cell counting kit-8 (CCK-8) assay. 5% DMAHDM or MDP-containing groups showed increased immediate μTBS compared with the control group. Nanoleakage showed that 5% DMAHDM or MDP-containing groups presented little amount of silver penetration, while the control group exhibited extensive silver uptake along the bonding interface after water storage aging. FTIR showed that the interaction between MDP and hydroxyapatite was not affected by DMAHDM, besides DMAHDM did not hamper the polymerization of the bonding agents. The adhesives added with DMAHDM inhibited biofilm formation and reduced the biofilm CFU and metabolic activity of Candida albicans and Streptococcus mutans ( P  < 0.05). No cytotoxic or slight cytotoxic effect was detected for the experimental materials used (MDP and 5% DMAHDM). The addition of DMAHDM along with MDP can obtain improved dentin bonding with increased antimicrobial performance.