Data sources The electronic databases MEDLINE, EMBASE, Google Scholar, the Cochrane Oral Health Group's Trials Register, and CENTRAL from 1946 to 31 March 2018 were searched to identify eligible studies. Information sources in the Grey literature were also searched.Study selection Randomised and non-randomised studies as well as retrospective studies irrespective of their language were selected by two reviewers independently.Data extraction and synthesis Data extraction and risk of bias assessments were performed by two reviewers independently. Data were synthesised qualitatively. Quantitative syntheses were not possible because of high heterogeneity.Results One randomised controlled trial, four cross-sectional studies, and three retrospective studies were selected according to the eligibility criteria. The quality of the evidence in the included studies was predominantly of low to moderate quality. All studies reported on Twitter, three on YouTube, two on Facebook and one study referred also to Google+, Pinterest, Instagram, and Internet Blogs. The included studies reported on the informational value of social media on various aspects of orthodontic treatment and patients' health experiences during orthodontic treatment.Conclusions The authors of this review concluded that social media represent a basic resource for exchanging knowledge on a wide variety of aspects of orthodontics.