Comparison of relapse of orthodontic treatment following aligner versus conventional fixed appliance treatment. A systematic review

Background: Aligners are an alternative that are currently being widely used in orthodontic treatment, however, post-treatment relapse following aligner versus conventional treatment has not been compared. The objective of this study was to compare post-treatment relapse of orthodontic treatment with dental aligners versus conventional fixed orthodontics through a systematic review. Materials and methods: An exhaustive search was carried out in the MEDLINE (via PubMed), EBSCO, SCOPUS and EMBASE databases up to September 30, 2023. A total of 522 articles were found and after applying the selection criteria, the full texts of 24 articles were chosen for evaluation. At the end of the evaluation, only 3 studies were considered, two observational studies and one randomized clinical trial. The Newcastle Ottawa and Risk of bias (ROB-2) tools were used to assess the risk of bias. Results: Of the three studies, only one (evaluated three years post-orthodontic treatment) identified significant differences in the frequency of relapse following total, maxillary and mandibular anterior alignment using conventional orthodontics. The other two studies (one evaluated at six months and the other two years post-orthodontic treatment) did not show statistically significant differences (p>0.05). In addition, the two latter studies reported slight relapse related to detachment of the fixed retainer. Conclusions: The current evidence available indicates a lack of well-designed studies comparing post-treatment orthodontic relapse following the use of dental aligners versus conventional fixed orthodontic treatment, and the studies published to date have a high or moderate risk of bias. However, there are apparently no significant differences in frequency of relapse between the two types of treatment, suggesting similar stability results. Nonetheless, more well-designed studies are required to confirm this observation.