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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.

The investigation of the efficiency of a handheld Plasma Gun (PG) in the decontamination of tooth root canals is here reported. The antibacterial efficacy of the PG was first assessed on Enterococcus faecalis contaminated agar plates to determine optimal operating conditions that were then quantitatively evaluated treating contaminated liquid suspensions. Moreover, two different procedures for the inactivation of bacteria in realistic tooth models, resembling procedures conventionally adopted in endodontic practice, were investigated: (A) irrigation of contaminated tooth models with plasma activated water (indirect treatment) produced using the PG and (B) direct exposure of the contaminated tooth models to the plasma plume produced by the PG (direct treatment). The experiments were performed with the root canal model both in wet (root canal filled with bacteria suspension) and in dry (root canal contaminated and dried) conditions. From the obtained results, the direct treatment under dry conditions turned out to be the most effective, leading to a bacterial load mean reduction of 4.1.