The Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, Scopus, Web of Science, Google Scholar, Trip, CINAHL via EBSCO, EMBASE via OVID and ProQuest searched up to June 2023. Any clinical study with parallel arms and matched malocclusion severity should include permanent dentition participants with mild to mild-to-moderate anterior crowding. Participants should have undergone orthodontic treatment with either orthodontic labial fixed appliances or removable clear aligners. Total treatment time (primary outcome), chair time, number of appointments, and emergency visits (secondary outcomes) should also be reported.
Two reviewers selected the studies to be considered in two stages. If needed, a third reviewer was included to solve discrepancies. Endnote and Rayyan software supported the process.
The same two reviewers independently extracted the required data from the included studies. If needed, a third reviewer was included to solve discrepancies. Endnote and Rayyan software supported the process.
Ten studies were finally included (six RCTs and four non-RCTs). Only one included samples in which teeth were extracted due to crowding. The total included sample was 718 participants (aged 20–29 years). Only one study did not report crowding equivalency between groups.
Based on low to very low certainty levels, treatment duration is likely similar, chair time and emergency visits are less frequent, and the number of appointments is increased with clear aligners.
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