Effectiveness of acid-electrolyzed functional water for oral care of the elderly: an in vitro study

Abstract Background: Aspiration pneumonia is a major cause of death in the elderly. Oral bacterial can contribute to the occurrence of this disease. It is therefore important to maintain oral cavity hygiene. However, tooth brushing is sometime difficult for elderly people. Acid-electrolyzed functional water (FW) is an efficient bactericide, and gargling with FW might therefore contribute to the effective prevention of aspiration pneumonia. We investigated the possible use of FW as a mouth rinse.Methods: The bactericidal effect of FW against each species of bacteria was evaluated using the numbers of colony-forming units. The test organisms were Staphylococcus aureus, Streptococcus pneumonia, Pseudomonas aeruginosa, and Candida albicans. The experiment was conducted using PBS as a control, LISTERINE, and ConCool F. We used two concentrations of ConCool F: undiluted, and the optimal concentration indicated by the manufacturer. To investigate the bactericidal mechanism of FW, the activity of superoxide dismutase, an indicator of oxidative action, was measured in S. aureus. FW was diluted with purified water to concentrations of 10, 30, 50, and 70%. The number of colony-forming units were measured for each concentration. XTT assays were performed using HSC-3 and HeLa cells, to examine the viability of the cells following treatment with FW. The same experiment was conducted with PBS, Listerine, and undiluted ConCool F.Results: No bacteria treated with FW, Listerine, or undiluted ConCool F formed colonies. However, the number of colony-forming units in bacteria treated with diluted ConCool F was equivalent to that of control, except for C. albicans. Superoxide dismutase activity peaked at a 50% concentration of FW, and was more than twice that of the control. A significant decrease in the number of colony-forming units was observed following 50% treatment. Since the peaks of the superoxide dismutase activity and the starting concentrations of the bactericidal effects coincided, the bactericidal effect of FW's might be related to their oxidative effects. Bacteria treated with FW had as higher a survival rate than the other two mouth rinses. Conclusions: Our results suggest that FW might be clinically applicable as a mouth rinse.