Effects of Atmospheric Fluorine-Containing Nonthermal Plasmas on Demineralization and Remineralization of Tooth Enamel

This study investigated the effects of atmospheric fluorine-containing nonthermal plasmas (FNTPs) on the demineralization and remineralization of tooth enamel. Atmospheric FNTPs were generated using a custom-made plasma device with a mixture of argon and 1,1,1,2-tetrafluoroethane as the feed gas. The resulting plasmas were characterized using optical emission spectroscopy and one was selected and used to treat tooth enamel. Energy-dispersive X-ray spectroscopy (EDX) analysis showedsignificantly increased fluorine contents in plasma-treated enamel surfaces. An acid etch biopsy test revealed increased fluoride contents at different depths beneath the surface of plasma-treated enamels when compared with the negative control group (i.e., without plasma treatment). In addition, the results ofEDX analysis showed that after a seven-day in vitro pH cycling experiment, those plasma-treated enamels still retained significantly increased levels of fluorine. Moreover, after a 14-day in vitro pH cycling experiment, polarized light microscopy revealed that plasma-treated tooth enamel had significantly shallower demineralization depth $(p =0.02$ ) and significantly larger remineralization bandwidth ( $p < 0.01$ ) when compared with the negative control group. The results from the present study suggest that atmospheric FNTPs might be an innovative and promising technique for prevention and treatment of dental caries via local fluoride delivery to effectively enhance remineralization of tooth enamel and inhibit its demineralization.