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The incorporation of polymerizable cationic monomers has been attempted to generate dental resinous materials with antibacterial activity. This study tested the hypothesis that a dental adhesive containing a cationic monomer, methacryloxylethyl cetyl dimethyl ammonium chloride (DMAE-CB), would influence biofilm formation and gtf gene expression of Streptococcus mutans. The effect of the photo-polymerized DMAE-CB-incorporated adhesive on in vitro biofilm accumulation was investigated with spectrophotometry and scanning electron microscopy. The relative level of gtf gene expression by Streptococcus mutans in the biofilm was quantified by real-time reverse-transcription polymerase chain-reaction. The DMAE-CB-incorporated adhesive significantly decreased bio-film accumulation on its surface (P < 0.05), and suppressed the expression of gtfB and gtfC of Streptococcus mutans in the biofilm (P < 0.05). The results suggest that the cured DMAE-CB-incorporated adhesive may hamper biofilm accumulation via selective down-regulation of the expression of gtf genes in Streptococcus mutans.

This study evaluated the antibacterial effect and microtensile bond strength of a resin-based adhesive containing an antibacterial monomer DMAE-CB (methacryloxylethyl cetyl dimethyl ammonium chloride). Cured specimens of 1, 2, and 3% DMAE-CB-containing Single Bond 2 (crosslinking monomer: Bis-GMA, dimethacrylates; functional monomer: HEMA) were prepared, and their antibacterial effects on Streptococcus mutans ATCC 25175 were investigated. Antibacterial property after 0, 30, 90, and 180 days of aging was also tested. Bonding ability of the experimental adhesive incorporating 3% DMAE-CB was evaluated by microtensile bond strength test. The cured experimental adhesive exhibited an inhibitory effect on S. mutans growth, and the adhesive containing 3% DMAE-CB showed higher antibacterial efficiency compared with those incorporating 1 or 2% anibacterial monomer. Antibacterial activities of the specimens lasted for at least 180 days. Microtensile bond strength test revealed that the bonding ability of the experimental adhesive was not significantly adversely affected by the incorporation of DMAE-CB. Therefore, dental adhesives with strong and long-lasting bacteriostatic property could be achieved by incorporating DMAE-CB without negatively influencing bonding ability.

The antibacterial properties of resins incorporating MAE-DB and the underlying mechanisms of action were evaluated. Antibacterial effects against Streptococcus mutans were tested using the film contact method, with accumulation and membrane integrity observed by scanning electron microscopy and confocal laser scanning microscopy, respectively. Quantitative PCR was used to determine expression of the S. mutans glucosyltransferase B (gtfB) gene on the surface of resins containing 10% MAE-DB. Bacterial growth was inhibited on resin containing 10% MAE-DB as compared with the control at 1 day, 7 days, 30 days, or 180 days (p < 0.05). For the 10%-MAE-DB resin, no significant differences in bacterial viability were found regardless of the time of incubation (p > 0.05). The number of bacteria attached to resin containing 10% MAE-DB was considerably lower than the control. The proportion of bacteria with damaged cell membranes was increased in the experimental resin over controls. Expression of gtfB was reduced by 10% MAE-DB compared with the control (p < 0.05). These findings demonstrate that MAE-DB can be incorporated into resin materials at sufficient concentrations for long-term antibacterial effects against S. mutans after polymerization by attenuating gtfB expression and impairing membrane integrity.

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