Cold atmospheric plasma treatment affects early bacterial adhesion and decontamination of soft reline palatal obturators

The aim of this work was to evaluate cold atmospheric plasma bactericide activity towards biofilm formation on soft reline oral palatal obturators. Plasma was generated using two dielectric barrier discharge and tested against the oral biofilm formers Streptococcus mutans and Aggregatibacter actinomycetemcomitans. Relines were either plasma treated before being infected with 24 h biofilm, or infected with 90 min (early) or 24 h (mature) biofilm prior to be plasma treated for 30, 60, or 120 s. Bacteria numbers and viability were evaluated by Colonies Forming Units counts (CFU) and quantitative colorimetric metabolic 2,3-bis (2-methoxy-4-nitro-5-sulphophenyl)-5-[(phenyl amino) carbonyl]-2H-tetrazolium hydroxide assay (XTT). cytocompatibility was assayed towards human primary fibroblasts and keratinocytes cultivated on plasma-treated specimens by colorimetric metabolic 3-(4,5-Dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide (MTT) assay and light microscopy. Results demonstrated that both plasma sources were effective. Plasma treatment of sterile reline affected bacterial adhesion, reducing CFU number and viability by 2 logs and by 50%, in comparison with untreated controls (p < 0.05). Plasma efficacy was marked against early biofilm: after 120 s, CFUs were reduced by 3 logs, and viability decreased by about 60% (p < 0.05). Significant results were also observed for mature biofilm: CFUs and viability were reduced by approximately 2 logs and 40% (p < 0.05), after 120 s exposure. Lastly, MTT did not show any toxic effect on human cells. Thus, plasma could represent a very promising skill for soft reline shutters decontamination.