Antimicrobial Effect of Fluoride-Generating Nonthermal Atmospheric Plasmas on In Vitro Triple-Species Oral Biofilms

This study investigates the feasibility of fluoride delivery via fluoride-generating nonthermal atmospheric plasma (FNTAP) and its antimicrobial effects on in vitro triple-species oral biofilms. FNTAPs were generated by adding 5 or 10 sccm (standard cubic centimeters per min) 1,1,1,2-tetrafluoroethane (TFE) to atmospheric argon (3000 sccm) nonthermal plasma (ArNTAP). Reactive plasma species were measured in plasma-treated phosphate-buffered saline (PBS). Twenty-four-hour biofilms were constructed from Streptococcus mutans, Streptococcus sanguinis, and Candida albicans for assessing the antimicrobial effects of FNTAPs via viability assays and colony-forming unit (CFU) assays. FNTAP treatments significantly increased the concentrations of F^- and NO₂^- in PBS compared to ArNTAP treatments (p < 0.01), and decreased the concentrations of H₂O₂ and NO₃^- in PBS (p < 0.001, p < 0.05). 5 sccm 2 min FNTAP treatment reduced biofilm viability by 94.12 ± 1.03% (p < 0.001), compared to a 69.32 ± 2.05% (p < 0.001) reduction with ArNTAP. CFU assays showed that FNTAPs were especially efficacious against C. albicans. 5 sccm 3 min FNTAP treatment reduced fungal log₁₀ CFUs by 4.28 ± 0.36 (p < 0.001). Fungal CFUs were below detectable levels for the 10 sccm 2 and 3 min groups, except for two data points in each group. In conclusion, FNTAP effectively produced measurable fluoride in PBS and significantly enhanced antimicrobial efficacy against triple-species biofilms, highlighting its potential as a multifunctional tool for caries control.