Antimicrobial efficacy of chlorhexidine and sodium hypochlorite in root canal disinfection: A systematic review and meta-analysis of randomized controlled trials

We aimed to compare the antimicrobial efficacy of chlorhexidine (CHX) and sodium hypochlorite (NaOCl), two irrigants routinely used in root canal therapy of permanent teeth.Electronic databases, including PubMed, EMBASE, Web of Science, and Cochrane Library, were searched for randomized controlled trials published until March 2020. The meta-analysis of relative risk (RR) and standardized mean difference (SMD) was performed using a random-effect model with a 95% confidence interval (CI). Subgroup analysis was performed for culture and molecular methods of bacterial detection.The literature search yielded 2,110 records without duplicates. Eight studies were eligible for a systematic review. No significant differences in the incidence of samples with positive bacterial growth after irrigation (RR=1.003, 95% CI: 0.729-1.380, p=0.987) and mean bacterial number changes (SMD=0.311, 95% CI: -0.368-0.991, p=0.369) were observed between CHX and NaOCl in the culture and molecular subgroups. Heterogeneity in RR (I2=0%, p=0.673) was low among studies, while considerable heterogeneity was observed in the analysis of SMD (I2=76.336%, p=0.005).Our findings suggest that both CHX and NaOCl can reduce bacterial infections after irrigation, without any significant difference in antimicrobial efficacy between them. Although CHX and NaOCl showed similar efficacy, their molecular mechanisms were different. Therefore, they can be used as the main antibacterial root canal irrigants. However, our results were limited by inconsistencies among retrieved articles and a lack of clinically relevant outcomes. Further well-designed clinical studies are warranted to supplement our results.