Dual function of anti-biofilm and modulating biofilm equilibrium of orthodontic cement containing quaternary ammonium salt.

The objectives of this study were to incorporate dimethylaminohexadecyl methacrylate (DMAHDM) into resin-modified glass ionomer cement (RMGI) to develop a novel orthodontic cement which endowed RMGI with strong antibacterial ability and investigated its modulation biofilm equilibrium from cariogenic state to non-cariogenic state for the first time. Cariogenic Streptococcus mutans (S. mutans), and non-cariogenic Streptococcus sanguinis (S. sanguinis) and Streptococcus gordonii (S. gordonii) were selected to form a tri-species biofilm model. RMGI incorporated with different mass fraction of DMAHDM was examined: biofilm colony-forming units, metabolic activity, live/dead staining, lactic acid and exopolysaccharides productions. TaqMan real-time polymerase chain reaction was used to determine changes of biofilm species compositions. The results showed RMGI containing 3% DMAHDM achieved strong antibacterial ability and suppressed the cariogenic species in biofilm, modulating biofilm equilibrium from cariogenic state to non-cariogenic state tendency. The novel bioactive cement containing DMAHDM is promising in fixed orthodontic treatments and protecting tooth enamel.