Novel Antibacterial Quaternary Ammonium Monomer Dimethylaminohexadecyl Methacrylate Endows Orthodontic Cement With Strong Antibacterial Capability

Objectives: Orthodontic treatment increases biofilm accumulation and therefore the incidence of white spot lesions. The objectives of this study were to develop an antibacterial orthodontic cement to inhibit demineralization by incorporating a novel quaternary ammonium monomer dimethylaminohexadecyl methacrylate (DMAHDM), and to evaluate its anti-biofilm activity and shear bond strength.
Methods: Novel antibacterial monomer DMAHDM was synthesized and incorporated into commercial orthodontic cement at 0%, 1.5% and 3% by mass. Anti-biofilm activity was assessed using a human dental plaque microcosm biofilm model, and metabolic activity, lactic acid production, and colony-forming units (CFU) on orthodontic cements were investigated. Shear bond strength of metal brackets to enamel surface was tested with ninety extracted human bicuspids. The adhesive remnant index (ARI) was also evaluated microscopically.
Results: Biofilm activity precipitously dropped when contacting orthodontic cement with DMAHDM. Orthodontic cement containing 3% DMAHDM significantly reduced biofilm metabolic activity and lactic acid production, and CFU of total microorganisms, total streptococci, and mutans streptococci decreased by two logs. Adding DMAHDM into orthodontic cement and aging for 30 days had no adverse influence on shear bond strength (P>0.1).
Conclusions: By incorporating DMAHDM for the first time, orthodontic cement obtained substantial antibacterial capability without compromising mechanical properties. Therefore, DMAHDM could be highly advantageous in reducing or eliminating demineralization during and after orthodontic treatment.