Purpose: To assess the clinical treatment effectiveness of clear aligners in orthodontic tooth movements.

Methods: The database of Cochrane Central Register of Controlled Trials, Embase, PubMed, Web of Science, and Scopus were searched from Jan 2015 to Jan 2020. The National Institute for Health and Clinical Excellence assessment tool was used for the methodological quality of included studies.

Results: The literature review yielded 166 articles after removal of duplicates, and an additional 2 articles were included from hand search of the bibliographies of included articles and relevant reviews. Fifteen studies were included in the systematic review. One study was randomized controlled trial, one study was prospective case-control study, two studies were retrospective case-control and eleven studies were retrospective cohort studies.

Conclusion: The clear aligner treatment (CAT) is effective in managing minor malocclusion. CAT could achieve a comparable treatment outcome to that of the fixed orthodontic appliance in nongrowing patients with mild malocclusion. There are weak evidences to support the efficacy of CAT in extraction orthodontics. The results should be interpreted with caution due to heterogeneity in studies.