Limited evidence on differences between fixed appliances and clear aligners regarding pain level.

Design Systematic review for randomised and non-randomised studies.Data sources Eight electronic databases: PubMed, Cochrane, Scopus, Web of Science, Lilacs, Google Scholar, Clinical Trials and OpenGrey were searched without language or date restrictions during the search, in addition to hand-searching.Study selection Randomised and non-randomised controlled trials (RCTs and non-RCTs) and cross-sectional studies that compare pain levels between fixed appliances and clear aligners during orthodontic treatment in adults patients.Data extraction and synthesis The reviewers followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The study selection was done by two reviewers. The reviewers assessed the risk of bias using three risk of bias tools (ROB.2 tool for RCTs, ROBINS-I tool for non-RCTs and the Newcastle-Ottawa scale for cross-sectional studies).Results Seven studies were included in this review. Five studies were non-RCTs, one was an RCT and one study was a cross-sectional design. The risk of bias was moderate to high in the non-RCTs, low in the RCT and low for the cross-sectional study. All studies used the same type of aligners (Invisalign aligner) and they differed in the fixed appliance type and archwire sequences. However, meta-analysis was not possible. In the first 24 hours of treatment, four studies revealed that the pain is higher in the fixed appliance group. During days three and four, two studies reported a higher level of pain in a fixed appliance group. On days five to seven, only one study reported a higher level of pain in a fixed appliance group. On day 14, two studies evaluated pain levels and reported that there is no difference between the two groups.Conclusions With low certainty, patients treated with clear aligners seems to have less pain perception than patients treated with conventional fixed appliances during the first days of treatment. There were no noticeable differences up to three months between the two groups. Furthermore, the malocclusion was not described in detail in the individual studies, which may play a role in pain level differences.