Ação do plasma de baixa temperatura em biofilmes em formação de Streptococcus mutans in vitro

Abstract

Low Temperature Plasma (LTP) is an innovative therapy that has been studied to develop new strategies for the prevention and / or treatment of infectious diseases related to the presence of oral biofilms, including dental caries. The objective of this study was to verify the effect of LTP on biofilms formed in vitro on human enamel. For this, biofilms of UA159 Streptococcus mutans were formed on blocks of human enamel (4 x 4 x 2 mm) exposed to episodes of sucrose simulating what occurs in the oral cavity. The blocks were divided into: ST (negative control); CHX 0.12% (Positive control); 0.05% NaF (Positive control); ARG1 (Argon 1 minute); ARG5 (Argon 5 minutes), ARG10. (Argon 10 minutes), PLA1 (Plasma 1 minute); PLA5 (Plasma 5 minutes); PLA10 (Plasma 10 minutes). Bacterial viability through the CFU / mg biofilm count showed a statistically significant difference between the groups (p <0.0001). The argon or LTP treatments at the three times tested significantly reduced the viability of bacteria present in biofilms. In the Confocal Laser Microscopy (CLM), the biofilms of the ST, NaF and ARG10 groups showed more areas stained in green (living), while the biofilms of the CHX, PLA1 and PLA 10 groups showed more red stained areas. Quantification of Soluble Extracellular Polysaccharides (EPS) showed no statistically significant difference between ST, NaF and ARG5 groups. All other groups promoted a significant reduction (p <0.05) in the amount of soluble EPS. There was no statistical difference between all groups for water insoluble EPSs. From the surface microhardness test, the percentage of the superficial hardness loss (%SHL) was calculated, with a significant reduction in the %SHL only for the CHX group (p <0.05). In addition, no statistically significant differences were found among Raman spectroscopy. In addition, the SEM showed no topographical difference in the enamel surface treated with LTP. In conclusion, we have found that the daily treatment with LTP was effective in reducing the amount of viable bacteria and the concentration of water soluble EPS; without altering the surface of the enamel under the irradiated biofilm.