Conventional vs ultrasonic irrigation - which leads to less post-operative pain?

Data sources Medline, Scopus, Web of Science, Embase, Cochrane Library, ClinicalTrials.gov and OpenGrey databases were systematically searched to find studies comparing post-operative pain experienced following root canal treatment with ultrasonic and conventional irrigation (up to May 2021). Hand searching of selected journals was also performed.Study selection Randomised controlled trials assessing post-operative pain experienced following primary non-surgical root canal treatment using conventional versus ultrasonic irrigation were screened. Exclusion criteria included an unsuitable follow-up period, systemic disease among the participants, severe pain, acute apical abscess diagnoses and fewer than 12 patients per trial arm. English language only studies were included. Two reviewers independently screened the studies and disagreements were resolved by consulting a third reviewer.Data extraction and synthesis Data extracted included tooth type, root type, pre-operative diagnosis, pain recording, time of pain recording, number of patients requiring analgesics and study conclusions. Meta-analyses of different post-operative time periods (6h, 24h, 48h, 72h and 7 days) were performed using a fixed-effects model to obtain a mean difference (with 95% confidence intervals) for post-operative pain. Heterogeneity between studies was evaluated using the I2 statistic. Quality assessment of the included studies was performed according to the Cochrane Collaboration protocol for randomised controlled trials. Publication bias was assessed using a funnel plot and modified via the 'trim-and-fill' method.Results A total of six articles were included in the systematic review, of which four were included in the meta-analysis. Overall risk of bias was deemed to be 'low' with one study presenting an unclear risk with respect to selection bias. Meta-analysis demonstrated that ultrasonic agitation significantly reduced post-operative pain compared to conventional irrigation at 6, 24 and 48 hours (p <0.05) but no significant differences were found at later time points.Conclusions Ultrasonic irrigation may lead to less post-operative pain compared to conventional irrigation techniques; however, the evidence base is limited and further research is needed to support these findings.