Abstract:【Abstract】Objective To investigate the antimicrobial effects of ozone water on four kinds of periodontal pathogens. Methods Four kinds of standard periodontal pathogens strains including Porphyromonas gingivalis (P.g.) ATCC 33277, Porphyromonas intermadia (P.i) ATCC 25611, Fusobacterium nucleatum (F.n) ATCC 10953, Actinomyces viscosus (A.v) ATCC 19246 were treated with different concentrations of ozone solution (0ppm, 105ppm, 211ppm, 391ppm) and 3% hydrogen peroxide solution for 30s and 60s. The total number of colonies was detected by the quantitative suspension method. The antimicrobial effects were compared among different treatments. Results Under the same treatment time, the total number of colonies of P.g ATCC33277, F.n ATCC10953, P.I ATCC25611 and A.v ATCC19246 treated with different solutions had statistic difference (P<005). Under the same treatment concentration, the total number of colonies of P.g ATCC33277, F.n ATCC10953, P.I ATCC25611 and A.v ATCC19246 treated with different time had no difference (P>005). The total number of bacterial colonies of P.g ATCC33277 treated with 105ppm ozone solution had statistic difference (P<005), while no difference was found under the treatment of 0ppm, 211ppm, 391ppm ozone solutions as well as the 3% hydrogen peroxide solution (P>005). The total number of bacterial colonies of A.v ATCC19246 treated with 391ppm ozone solution had statistic difference (P<005), while no difference was found under the treatment of 0ppm, 211ppm, 105ppm ozone solutions as well as the 3% hydrogen peroxide solution (P>005). Conclusion Ozone water has a concentrationdependent bactericidal effect on P.g ATCC33277, F.n ATCC10953, P.i ATCC25611, A.v ATCC19246.