Li, F., Weir, M.D., Xu, H.H.K.

The objectives of this study were to synthesise new quaternary ammonium methacrylates (QAMs) with systematically varied alkyl chain lengths (CL), and to investigate, for the first time, the CL effects on antibacterial efficacy, cytotoxicity, and dentin bond strength of bonding agents. QAMs were synthesised with CL of 3 to 18and incorporated into Scotchbond Multi-Purpose (SBMP) bonding agent. The cured resins were inoculated with Streptococcus mutans. Bacterial early attachment was investigated at four hours. Biofilm colony-forming units (CFU) were measured after two days. With CL increasing from 3 to 16, the minimum inhibitory concentration and minimum bactericidal concentration were decreased by five orders of magnitude. Incorporating QAMs into SBMP reduced bacterial early attachment, with the least colonisation at CL = 16. Biofilm CFU for CL = 16 was 4 log lower than SBMP control (p<0.05). All groups had similar dentin bond strengths (p>0.1). The new antibacterial materials had fibroblast/odontoblast viability similar to that of commercial controls. In conclusion, increasing the chain length of new QAMs in bonding agents greatly increased the antibacterial efficacy. A reduction in Streptococcus mutans biofilm CFU by 4 log could be achieved, without compromising bond strength and cytotoxicity. New QAM-containing bonding agents are promising for a wide range of restorations to inhibit biofilms.

Journal of Dental Research 2013; 92 (10): 932-938.