Bactericidal Effects of 2 Kinds of Oxidized Water with Different Chlorine Concentrations

Hard oxidized water (HOW), pH 2.0-3.0, containing 10-50 ppm chlorine and which has been shown to exert strong bactericidal effects within a short time, has been investigated in terms of its usefulness for controlling plaque formation. However, HOW has been associated with the problems of deterioration of metallic restorations and the demineralization of in situ teeth. The purpose of this study was to determine the bactericidal effects of soft oxidized water (SOW), pH 5.0-5.5 at chlorine concentrations ranging from 50 to 80 ppm on microorganisms in vitro . Twelve strains of 12 species of microorganisms, including 1 strain of Bacillus subtilis, were cultured in broth until the late logarithmic phase and centrifuged to obtain samples in tubes. After the samples had been cultured with SOW or HOW for 10 sec to 10 min, sodium thiosulfate was added to the tubes to stop the effect of each type of oxidized water. Samples were spread over the surfaces of agar plates and incubated aerobically for 48 hours at 37... Bactericidal effects were evaluated in terms of whether or not colonies formed on the agars. HOW displayed no effect on B. subtilis, but SOW displayed bactericidal effects on all microorganisms tested. The results show that SOW has a stronger bactericidal effect than HOW.