LAUSR

OBJECTIVES White spot lesions due to biofilm acid-induced enamel demineralization are prevalent in orthodontic treatments. The aim of this study was to develop a novel bioactive multifunctional cement with protein-repellent, antibacterial and remineralizing capabilities, and investigate the effects on enamel hardness and lesion depth in vitro for the first time. MATERIALS AND METHODS 2-Methacryloyloxyethyl phosphorylcholine (MPC), dimethylaminohexadecyl methacrylate (DMAHDM), and nanoparticles of amorphous calcium phosphate (NACP) were incorporated into a resin-modified glass ionomer (RMGI). Extracted human premolars had brackets bonded via four groups: (1) Transbond XT (TB), (2) RMGI (GC Ortho LC), (3) RMGI+MPC+DMAHDM, (4) RMGI+MPC+DMAHDM+NACP. Demineralization was induced via a dental plaque microcosm biofilm model. Samples were tested using polarized light microscopy (PLM) for lesion depth. Enamel hardness was tested for different groups. RESULTS Incorporating MPC, DMAHDM and NACP did not affect enamel bond strength. "RMGI+MPC+DMAHDM+NACP" group had the least lesion depth in enamel (p<0.05). Groups with NACP had the highest enamel hardness (p<0.05). Mineral loss (ΔS) in enamel for NACP group was about one third that for RMGI control. "RMGI+MPC+DMAHDM" had greater effect on demineralization-inhibition, compared to RMGI and TB controls. "RMGI+MPC+DMAHDM+NACP" was more effective in protecting enamel prisms from dissolution by biofilm acids, compared to RMGI and TB control groups. CONCLUSION The Novel "RMGI+MPC+DMAHDM+NACP" cement substantially reduced enamel demineralization adjacent to orthodontic brackets, yielding much less lesion depth and greater enamel hardness under biofilm acid attacks than commercial controls. The clinical significance is that the novel multi-agent (RMGI+MPC+DMAHDM+NACP) method is promising for a wide range of preventive and restorative applications to combat caries.