We assessed the antimicrobial activity of an atmospheric pressure,room-temperature plasma in a simulated root canal infected with Enterococcus faecalis.One hundred and four single-rooted plastic resin blocks were instrumented using K-files from size 15 to 40 using the step-back technique.The blocks were autoclaved,inoculated with an Enterococcus faecalis suspension,and incubated for 72 h.