Effects of Electrolyzed Water on the Growth of Oral Pathologic Bacteria Species and its Cytotoxic Effects on Fibroblast and Epithelial Cells at Different pH Values

Background: Microbial plaque-induced oral diseases are among the most common diseases worldwide. The present study aimed to compare the antimicrobial effect of electrolyzed water (EW), (acidic, mildly basic, and basic) on the growth of bacterial species producing dental plaque and to assess their cytotoxicity on fibroblasts and epithelial cells. Methods: The study was performed at Shahid Beheshti University of Medical Sciences in 2019. Several bacterial species (Streptococcus salivarius, Staphylococcus aureus, Lactobacillus casei, and Aggregatibacter actinomycetemcomitans) were treated with different EW types at three pH values (3, 9, and 11) for 30 seconds and subsequently, the colonies were counted. The cytotoxic effect of these EW types was evaluated on HeLa and L929 cell lines at 30 seconds, 1 minute, and 5 minutes. GraphPad Prism 6.0 was used for statistical analysis. The Kruskal-Wallis test followed by Mann-Whitney U and oneway analysis of variance followed by Tukey’s test were used to analyze bacterial activity and cell cytotoxicity, respectively. P<0.05 was considered statistically significant. Results: EW types significantly inhibited bacterial growth at all pH values. The strongest antibacterial activity of EW was against A. actinomycetemcomitans (P<0.001) and the least significant antibacterial activity was against S. aureus (P<0.001). The EW types showed increased cytotoxic activity against L929 cells as the treatment time increased. The most cytotoxic effect was seen at 5 minutes of treatment in all EW types compared with the negative control group (P<0.0001). This negative cytotoxic effect on HeLa cells was shown just after 30 seconds and viable cell counts increased over time, reaching its highest value at 5 minutes of treatment with basic EW (P<0.0001). Conclusion: The contradictory effects of the EW types on both HeLa and fibroblasts, in addition to variable results at different exposure times, indicated that the effect of EW could vary depending on cell types and treatment periods.