The bonding property and cytotoxicity of a dental adhesive incorporating a new antibacterial monomer.

The incorporation of polymerisable cationic monomers has been attempted to generate dental resinous materials with antibacterial activity. This study tested whether the incorporation of a cationic monomer, methacryloxylethyl cetyl dimethyl ammonium chloride (DMAE-CB), into a commercial dental adhesive would influence the bonding property and biocompatibility of the parental adhesive, and whether DMAE-CB could leach out from the cured modified adhesive. Microtensile bond strengths of DMAE-CB-incorporated adhesive and its parental adhesive to dentin were compared. Dentin discs bonded with modified adhesive were incubated in artificial saliva at three different temperatures for 90 days to obtain eluents. The cytotoxicity of DMAE-CB monomer and adhesive eluents were tested with 3-(4, 5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cleavage assay (MTT assay). High-performance liquid chromatography (HPLC) was performed with the eluents of the modified adhesive. The results indicated that the incorporation of DMAE-CB into the dental adhesive did not adversely influence its bonding strength to dentin (P > 0·05). Although DMAE-CB monomer exhibited toxicity against L929 cells at the concentration of 2 μg mL(-1) or higher (P < 0·05), the eluents of DMAE-CB-incorporated adhesive did not show significant influence on cell growth (P > 0·05). Moreover, HPLC analysis detected four substances' peak baseline separation for the eluents of modified adhesives, which was identical to the eluent of the parental adhesive, indicating no detectable DMAE-CB monomer leaching even after soaking for 90 days. Those results suggest that DMAE-CB could be incorporated into the dental adhesive stably without compromising the bonding efficiency and biocompatibility of its parental adhesive.