Abstract: The goal of this bachelor thesis was to test the efficacy of plasma activated water (PAW) and direct effect of cold plasma of corona discharge for the inactivation of Enterococcus faecalis, bacterium most often found in infected root canals. In the first set of experiments we compared the effects of saline solution, sodium hypochlorite NaOCl and PAW on bacteria in vitro. We also tested the effect of different time exposures of these treatments. Our goal in the next type of experiments was to model a situation in infected root canals. For this intention we used sterile ex vivo single root teeth (incisors and canines) infected by Enterococcus faecalis and afterwards we compared the effects of saline solution, sodium hypochlorite, PAW and direct effect of corona discharge with constant time exposure to infected root canals. We used two parameters for evaluation of the treatment efficacy – logarithmic reduction and percentual effectiveness.