Evaluation of antibacterial activity of an experimental dental adhesive containing synthesized quaternary ammonium compound: in vitro study

Background Dental adhesives with immobilized antibacterial agents are formulated to combat bacterial invasion along the tooth-restoration interface. This study aims to evaluate the antibacterial effect of synthesized quaternary ammonium compound (QAC) incorporated into commercial dental adhesive. Methods QAC was synthesized from 2-(Dimethylamino) ethyl methacrylate and 1-Bromobutane and characterized using CHN (Carbon, Hydrogen, Nitrogen), FTIR (Fourier transform infrared) and H+NMR (Proton nuclear magnetic resonance) analyses. The synthesized QAC was assessed for its cytotoxicity and its antibacterial activity against S. mutans using disc diffusion method, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), time-kill kinetics test, and TEM imaging. The QAC was added to the primer of a commercially available adhesive (OptiBond XTR) at two concentrations; 20 and 40 mg mL(-1) representing the MIC and MBC, respectively. The antibacterial properties of the experimental adhesives, commercial antibacterial adhesive Clearfil SE Protect containing 12-methacryloyloxydodecylpyridinium bromide (MDPB), and commercial vehicle (OptiBond XTR) were compared using time-kill kinetics test. Statistical analysis by ANOVA followed by tukey post-hoc test (P < 0.05). Results Disc diffusion and time-kill kinetics tests showed potent antibacterial action of QAC, both in the unpolymerized and the cured forms. MIC and MBC were 20 and 40 mg mL-1 respectively. There was no statistically significant difference between experimental adhesives and Clearfil Protect with more than 99% reduction in bacterial count, while OptiBond XTR showed no bacterial killing up for up to 10 h. Conclusions The synthesized QAC added to a commercially available adhesive imparted antibacterial properties, thus providing an affordable adhesive system to the local market.