Forty freshly extracted single-rooted teeth were prepared to a size 25 master apical file, autoclaved, and inoculated with a known quantity of Actinomyces naeslundii. The teeth were divided into four groups (n = 10), including an untreated control group. The three treatment groups were exposed to Micro Plasma System (MPS), 0.5% NaOCl and 0.5% NaOCl + MPS respectively. The content of each root canal was absorbed by sterile paper points, diluted in 2 ml Schaedler Broth Medium, and incubated on blood agar. The number of CFU was determined. Data analysis, using an analysis of variance and Scheffe's test at the 1% level (Statview II software), indicated a significant reduction in CFU count for the three treatment groups compared to the control group. For the three treatment groups, no significant intergroup differences were observed.