Postoperative pain after endodontic treatment with glycolic acid as final irrigant using reciprocating and rotary instrumentation in a noninferiority trial.

This randomized clinical trial was designed to evaluate whether glycolic acid (GA) is non-inferior to ethylenediaminetetraacetic acid (EDTA) regarding postoperative pain after endodontic treatment. A total of 240 patients requiring treatment were randomly assigned to four groups according to the irrigant (GA or EDTA) and the instrumentation technique (reciprocating or rotary). Postoperative pain was assessed using the numeric rating scale (NRS, 0–10) at 24 h, 48 h, and 7 days. A non-inferiority margin (Δ = 0.9) was prespecified as the maximum acceptable difference between GA and EDTA. Non-inferiority was concluded if the upper bound of the one-sided 95% confidence interval (equivalent to the two-sided 90% CI) for the difference in means (GA – EDTA) was below Δ. Analgesic intake was also recorded. Postoperative pain peaked at 24 h and significantly decreased over time (p < 0.001). At all evaluated time points, the upper bound of the one-sided 95% confidence interval for the difference between GA and EDTA remained below Δ, demonstrating that GA was non-inferior to EDTA. Exploratory two-sided analyses revealed no significant differences in pain intensity between irrigants or instrumentation techniques (p > 0.05). Most patients reported absent or mild pain, and 79.2% did not require analgesics, with no significant difference among groups (p = 0.616). GA is non-inferior to EDTA in terms of postoperative pain following endodontic treatment, regardless of instrumentation technique. Both irrigants provided similar clinical outcomes, with low analgesic intake and favorable patient-centered results. Trial registration number. Brazilian Clinical Trials Registry (ReBec). Registration number RBR-44q9k6q. (Retrospectively registered: October 17, 2023).