The effect of cryotreated sodium hypochlorite irrigation at different concentrations on postoperative pain in mandibular first molars with symptomatic irreversible pulpitis: a randomized controlled clinical trial

The purpose of this study was to evaluate the effects of cryotreated 2.5% and 5% sodium hypochlorite (NaOCl) on postoperative pain during endodontic treatment procedures in mandibular first molars with symptomatic irreversible pulpitis. One hundred and thirty two patients with permanent mandibular first molars diagnosed with symptomatic irreversible pulpitis were included in the study. The teeth were randomly divided into four groups: the normal 2.5% NaOCl group (n = 33), the cryotreated 2.5% NaOCl group (n = 33), the normal 5% NaOCl group (n = 33) and the cryotreated 5% NaOCl group (n = 33). In the normal NaOCl groups, the root canals were irrigated with NaOCl solution at 25 °C at all stages of the root canal treatment. In the cryotreated NaOCl groups, the root canals were irrigated with NaOCl solution at 2 °C at all stages of the root canal treatment. The participants were asked to rate the intensity of their postoperative pain via a Visual Analog Scale (VAS) at 6 h, 12 h, 24 h, 48 h, and 72 h. The data were analyzed using the Shapiro-Wilk, Levene’s, Kruskal Wallis H and the Chi-square test. The basic demographic data, preoperative pain values and analgesic intake of the four study groups were similar. Postoperative pain levels at 6 h were significantly lower in the cryotreated 2.5% NaOCl group than in all the other groups (p < .05). Postoperative pain levels at 12 h were statistically similar between the cryotreated 2.5% NaOCl group and the cryotreated 5% NaOCl group (p > .05) and significantly lower than those in the other two groups (p < .05). Using cryotreated NaOCl irrigation at different concentrations during root canal treatment procedures in mandibular first molars with symptomatic irreversible pulpitis effectively reduced postoperative pain. This study was registered at ClinicalTrials.gov (NCT06820996) on 11 February 2025.