Microbicidal effect and storage stability of neutral HOCl-containing aqueous gels with different thickening/gelling agents

Electrolyzed waters, containing mainly hypochlorous acid, are used in dental practice because of their high microbicidal effect. For wider use, three neutral electrolyzed water-based gels, namely, HOCl-containing aqueous gels were prepared with a thickening/gelling agent in this study. We evaluated their microbicidal effects against four strains and storage stabilities indicated by available chlorine concentration. Immediately after preparation, all gels (70 ppm) could completely remove microbes by a 3-min treatment. The gel prepared with xanthan gum remarkably reduced its available chlorine concentration even under shaded and refrigerated storage conditions, failing to maintain its microbicidal effect following 1-day storage, whereas other gels, prepared with carboxyvinyl polymer or agar, maintained effective concentration (>20 ppm), with high microbicidal effects following 9-day and 21-day storage, respectively. Neutral electrolyzed water-based gels might be useful to remove oral microbes. Based on our results, agar is the most suitable thickening/gelling agent from the viewpoint of storage stability.