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

Abstract

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.

Electrolysed oxidising water as a multi‐purpose biocide in dental healthcare—A scoping review

“…Storage‐related changes to POU EOW properties were reported in only four studies 57–60 ; one study evaluated RTU preparations 61 and one study compared various POU and RTU preparations 62 (Table S2). Properties of POU EOW 57–60 were measured over periods ranging from 21 to 120 days under various storage conditions (open/closed/dark, 57 room temperature/refrigerated, 58,60 capped/uncapped bottles, transparent/opaque bottles, 58,60 exposed/shaded to/from sunlight and the presence/absence of headspace within bottles 59 ). Three studies concomitantly evaluated antimicrobial efficacy 57,58,60 .…”

“…Properties of POU EOW 57–60 were measured over periods ranging from 21 to 120 days under various storage conditions (open/closed/dark, 57 room temperature/refrigerated, 58,60 capped/uncapped bottles, transparent/opaque bottles, 58,60 exposed/shaded to/from sunlight and the presence/absence of headspace within bottles 59 ). Three studies concomitantly evaluated antimicrobial efficacy 57,58,60 . The single storage‐related report on RTU neutral‐pH EOW, measured pH and antimicrobial activity following 1 week of storage in the light 61 .…”

“…Measurements included liquid (suspension) assays, agar diffusion assays and anti‐biofilm assays. Liquid growth/viability assays were performed either as stand‐alone procedures or prior to anti‐biofilm activity measurements (30 reports 9,50,57,58,60–85 ) and as a comparative method in one 86 of the four reports that investigated EOW effectiveness by agar diffusion assays 66,86–88 . In vitro adherence and anti‐biofilm assays (36 reports) were performed using laboratory biofilm models (11 reports, 70,73–75,77–79,89–92 ), extracted human teeth (14 reports 90,91,93–104 ), bovine teeth (1 report 105 ) and biomaterial substrates (10 reports 24,61,83,106–112 ).…”

“…The time since manufacture and pre‐test storage conditions of RTU EOW on study outcomes were reported in only 2 of the 27 reports 128,164 . Storage‐related investigations are sparse in general healthcare 166 and in dental healthcare 57–60,62 . One report 58 indicates faster chlorine loss from strongly‐acidic EOWs compared to moderate‐ and neutral‐pH EOWs.…”

“…Storage-related changes to POU EOW properties were reported in only four studies [57][58][59][60] ; one study evaluated RTU preparations 61 and one study compared various POU and RTU preparations 62 (Table S2).…”