Novel Orthodontic Cement Containing Dimethylaminohexadecyl Methacrylate With Strong Antibacterial Capability

Objectives: Orthodontic treatments are increasingly popular, especially among young people. However, orthodontic appliances tend to accumulate dental plaque at brackets and tubes, leading to enamel demineralization and white-spot lesions. The objectives of this study were to develop a novel antibacterial orthodontic cement to inhibit enamel demineralization by incorporating a new quaternary ammonium dimethylaminohexadecyl methacrylate (DMAHDM), and evaluate enamel shear bond strength and biofilm properties.
Methods: DMAHDM was synthesized and incorporated into Transbond XT (3M) at 0% (TB control), 1.5wt% and 3wt%. Shear bond strength of metal brackets to enamel was tested using extracted human bicuspids. Adhesive remnant index (ARI) was evaluated microscopically. Anti-biofilm activity was assessed using human saliva plaque microcosm biofilms. Metabolic activity, lactic acid production, and colony-forming units (CFU) of biofilms on orthodontic cements were investigated.
Results: Adding DMAHDM into orthodontic cement and water-aging for 90 days had no adverse influence on enamel shear bond strength (p>0.1). At 15 minutes, the bond strengths of TB control and TB+3%DMAHDM were (10.3±1.5) MPa and (12.0±1.9) MPa, respectively (p>0.1). At 90 days, bond strengths of TB control and TB+3%DMAHDM were (14.0±1.4) MPa and (13.8±2.0) MPa, respectively (p>0.1). Dental plaque microcosm biofilm growth was precipitously reduced when contacting orthodontic cement with DMAHDM. Cement containing 3% DMAHDM reduced biofilm metabolic activity and lactic acid by an order of magnitude (p<0.05). Biofilm CFU were reduced by two orders of magnitude for total microorganisms (reduced from nearly 10¹⁰ to 10⁸), total streptococci (from 10⁹ to 10⁷), and mutans streptococci (from 10⁸ to 10⁶) (p<0.05).
Conclusions: The novel DMAHDM-containing orthodontic cement was strongly antibacterial, reducing human dental plaque microcosm biofilm CFU by two orders of magnitude. DMAHDM incorporation and water-aging for 90 days had no adverse effect on bond strength. DMAHDM is promising for application in various orthodontic cements/adhesives to inhibit enamel demineralization and white-spot lesions.