Postoperative pain in root canal treatment with ultrasonic versus conventional irrigation: a systematic review and meta-analysis of randomized controlled trials.

Objective: The objective of this systematic review and meta-analysis (SRM) was to answer the question whether the use of ultrasonic irrigation (UI) results in less postoperative pain (PP) compared to conventional irrigation (CI).

Methods: A literature search was performed within the main scientific databases carried out until May 2021. The eligibility criteria were randomized clinical trials (RCTs). Meta-analysis was conducted using R software with the "META" package, the mean difference (MD) measure of effect was calculated, and the fixed effect model was applied with a 95% confidence interval (CI). The Cochrane collaboration scale was used to assess risk of bias and the GRADE tool to assess the quality of evidence.

Results: Six RCTs were included for systematic review and four for meta-analysis. UI resulted in less PP in 3 of 5 periods, at 6 h (MD - 1.40 [CI - 2.38 to - 0.42] p = 0.0052), 24 h (MD - 0.73 [CI - 1.07 to - 0.39] p = 0.0001), and 48 h (MD - 0.36 [CI - 0.59 to - 0.13] p = 0.022). However, PP showed no significant differences between the groups at 72 h and 7 days (p > 0.05). A low risk of bias was observed for most domains, except allocation that was considered unclear. The certainty of evidence was classified as moderate (24 h, 48 h, and 7 days) and low (6 and 72 h).

Conclusion: Within the limitations of this SRM, UI presented less occurrence of PP than CI. Further randomized clinical trials are needed to corroborate these findings.

Clinical Relevance: UI should be used by clinicians as it reduces postoperative pain in patients undergoing endodontic treatment.