Effect of sodium hypochlorite solution and gel with/without passive ultrasonic irrigation on Enterococcus faecalis, Escherichia coli and their endotoxins

<ns4:p> <ns4:bold>Background:</ns4:bold> Sodium hypochlorite (NaOCl) is the most commonly used irrigant in endodontics <ns4:bold>.</ns4:bold> The purpose of this study was to evaluate the effect of NaOCl solution (2.5%) and gel (3%) with/without passive ultrasonic irrigation (PUI) on <ns4:italic>Enterococcus faecalis, Escherichia coli,</ns4:italic> and their endotoxins, lipopolysaccharide (LPS) and lipoteichoic acid (LTA). </ns4:p> <ns4:p> <ns4:bold>Methods:</ns4:bold> 40 human lower premolars were contaminated with <ns4:italic>E. coli</ns4:italic> (ATCC 25922) for 28 days and <ns4:italic>E. faecalis</ns4:italic> (ATCC 29212) for 21 days. Specimens were randomly divided into four groups: (1) 2.5% NaOCl irrigating the canals without PUI activation; (2) 2.5% NaOCl with PUI; (3) 3% NaOCl gel irrigating the canals without PUI; and (4) 3% NaOCl gel with PUI. 40 mL of irrigant was used for each group. PUI activation was carried out using E1-Irrisonic stainless-steel tip at 10% frequency. After treatment, all specimens were filled with 3mL of 17% ethylenediaminetetraacetic acid (EDTA) for 3min and then washed with nonpyrogenic saline solution. Three samples were collected from the canals: S1, at baseline to confirm biofilm formation; S2 after treatment; and S3 after EDTA. Samples were assessed for <ns4:italic>E. coli</ns4:italic> and <ns4:italic>E. faecalis</ns4:italic> colony forming units, and LPS and LTA were assessed using chromogenic kinetic LAL assay and ELISA, respectively. Data were analyzed by Kruskal-Wallis, Friedmann and Dunn tests with α≤0.05. </ns4:p> <ns4:p> <ns4:bold>Results</ns4:bold> : All groups were effective in reducing the microbial load of <ns4:italic>E. coli</ns4:italic> and <ns4:italic>E. faecalis</ns4:italic> after treatment without a significant difference among the groups. NaOCl and NaOCl gel groups had no significant difference in reducing LPS and LTA. Statistically increased reduction was seen for NaOCL + PUI and NaOCl gel + PUI compared for groups without PUI. </ns4:p> <ns4:p> <ns4:bold>Conclusions:</ns4:bold> NaOCl gel has the same antimicrobial action of NaOCl solution and can partially detoxify endotoxins. PUI improves NaOCl (gel or solution) action over <ns4:italic>E. faecalis</ns4:italic> and <ns4:italic>E. coli</ns4:italic> and their endotoxins. </ns4:p>