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.

BACKGROUND: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: Using cryotreated NaOCl irrigation at different concentrations during root canal treatment procedures in mandibular first molars with symptomatic irreversible pulpitis effectively reduced postoperative pain. TRIAL REGISTRATION: This study was registered at ClinicalTrials.gov (NCT06820996) on 11 February 2025.