Sodium Hypochlorite Concentration and Postendodontic Pain - Unveiling the Optimal Balance: A Systematic Review and Meta-Analysis.

Introduction: This study systematically reviewed literature regarding the effect of different concentrations of sodium hypochlorite (NaOCl) used during root canal treatment (RCT) on postendodontic pain (PEP) and rescue analgesia.

Methods: Following registration with PROSPERO (CRD42023388916), a search was conducted using PubMed, Scopus, Web of Science, and Embase databases. Randomized controlled trials of patients receiving RCT which assessed PEP at different time intervals were included. Following data extraction and Cochrane risk of bias assessment 2, meta-analyses were performed to evaluate PEP during the first 48 hours along with rescue analgesic intake. The certainty of the evidence was evaluated using the Grading of Recommendations, Assessment, Development, and Evaluation approach.

Results: Five randomized controlled trials with 674 patients were included. One study exhibited a low risk of bias, while 4 raised some concerns. Patients treated with low concentrations of NaOCl (≤3%) were significantly less likely to report PEP at 24 hours (OR = 2.32; [95% CI, 1.63-3.31]; P < .05) and 48 hours (OR = 2.49; [95% CI, 1.73-3.59]; P < .05) as compared with high concentrations of NaOCl (≥5%). Furthermore, with low concentrations of NaOCl, significantly lesser moderate-severe PEP was reported at 24 hours (OR = 2.32; [95% CI, 1.47-3.62]; P < .05) and 48 hours (OR = 2.35; [95% CI, 1.32-4.16]; P < .05) and lesser analgesia was needed (OR = 2.43; [95% CI, 1.48-4.00]; P < .05).

Conclusions: While PEP can be influenced by several factors, low certainty evidence suggests that when NaOCl is used as an irrigant during RCT, PEP may be less likely with lower concentrations of NaOCl. Moderate certainty evidence indicates that lesser analgesia may be required with lower concentrations of NaOCl. These results should be cautiously interpreted.