N-acetylcysteine antimicrobial action against endodontic pathogens—systematic review and meta-analysis

Effective root canal disinfection is crucial for the success of endodontic treatment. N-acetylcysteine (NAC), known for its antimicrobial properties, has recently been investigated as a potential endodontic irrigant or intracanal medication. This systematic review aims to assess the antimicrobial efficacy of NAC in comparison to sodium hypochlorite, chlorhexidine, and calcium hydroxide against endodontic pathogens. A comprehensive search was conducted in PubMed, Scopus, Web of Science, Cochrane Library, and LILACS databases up to April 2024, without language or date restrictions. The PICO strategy for this review were as follows: population—teeth requiring endodontic treatment; intervention—NAC used as an endodontic irrigant or intracanal medication; comparison—sodium hypochlorite, chlorhexidine, and calcium hydroxide; Outcomes: reduction in microbial load, encompassing clinical and in vitro studies. Risks of bias assessment and data extraction were conducted with two reviewers independently selecting studies, extracting data, and assessing risk of bias. A general meta-analysis was performed across all included studies, with additional meta-analyses evaluating different exposure times, NAC concentrations, control groups and evaluation methods. After removing duplicates, 9170 studies were initially identified, and seven in vitro studies were included in the systematic review, of which five were included in the meta-analysis. Data were compared using standardized mean differences within a random-effects model. No clinical studies using NAC as an antimicrobial agent were identified. The overall meta-analysis demonstrated that NAC effectively reduced Enterococcus faecalis. Further meta-analyses revealed that exposure time, NAC concentration and choice of control group significantly influenced NAC’s effectiveness. NAC effectively reduced Enterococcus faecalis, showing comparable antimicrobial activity to CHX and NaOCl, especially at concentrations of 25–50 mg/mL over a 7-day exposure. Despite significant heterogeneity across studies, NAC demonstrated satisfactory antimicrobial effects in vitro. This suggests that NAC merits reconsideration as an effective intracanal medication for clinical use.