Electrolyzed Waters with Different Hypochlorite Concentrations in Controlling Cariogenic Biofilms

Objective: This study was designed to evaluate the efficacy of electrolyzed waters containing different hypochlorite (HClO) concentration levels on cariogenic biofilm controlling activities. Methods: Electrolyzed hypochlorite water (PerfectPerio water; PPW, Noguchi Dental Medical Research Institute, Tochigi, Japan), PPW was diluted; x10 (10-PPW), x100 (100-PPW) and x1000 (1000-PPW). In addition, electrolyzed low acid water (ELW; pH5.5) and electrolyzed strong acid water (ESW; pH2.5) were produced by a water electrolysis device (TK7705, National, Japan). Milli-Q water (MW) was included as controls. Pellets of the cariogenic bacteria were prepared from fresh cultures and resuspended in the above waters and incubated for 10 sec at room temperature. Viability of the bacteria was assessed by staining with BacLight bacterial viability kit followed by fluorescence microscopy and counting colony forming units (CFU/ml). To investigate effects on biofilms, sucrose dependent artificial biofilms were grown on equal-sized bovine enamel coupons using three species of freshly cultured cariogenic bacteria (Streptococcus mutans MT8148, Streptococcus sobrinus 6715 and Streptococcus gordonii ATCC10558) at 37°C for 12 hrs in an oral biofilm reactor. After a rinse in PBS the coupons were inoculated in above waters followed by shaking and measurements of retained and detached biofilms. Water insoluble glucan (WIG) of the biofilms were measured by using Phenol-H₂SO₄ method. Results: BacLight viability test showed that almost all bacteria were killed by original PPW (HClO = 600ppm). One way ANOVA and Tukey's HSD indicated significant reductions in the CFU counts down until 10-PPW dilution compared to other waters (p<0.05). In addition, a considerably larger amount of biofilms was detached (dissolved WIG) by the original concentration of PPW compared to ELW or ESW. Conclusion: PPW have proven to be a potential bactericide and it also dissolves WIG up to a considerable amount. Therefore, it is suggested that appropriate use of PPW would definitely be beneficial and careful application is important for safe caries control. More investigations are in progress in this regard. This study was supported by COE Program, FRMDRTB at TMDU and Noguchi Dental Medical Research Institute, Tochigi, Japan.