Retention period after treatment of posterior crossbite with maxillary expansion: a systematic review

OBJECTIVE: The aim of this systematic review was to evaluate the duration of the retention period in growing patients undergoing maxillary expansion and its relation with posterior crossbite stability. METHODS: Search strategies were executed for electronic databases Cochrane Library, Web of Science, PubMed and Scopus, which were completed on January 15, 2016. The inclusion criteria included randomized, prospective or retrospective controlled trials in growing subjects with posterior crossbite; treated with maxillary expanders; retention phase after expansion; post-retention phase of at least 6 months. The exclusion criteria were anterior crossbite, craniofacial anomalies, surgery or another orthodontic intervention; case reports; author's opinions articles, thesis, literature reviews and systematic reviews. The risk of bias of selected articles was assessed with Cochrane risk of bias tool for RCTs and Downs and Black checklist for non-RCTs. RESULTS: A total of 156 titles/abstracts was retrieved, 44 full-texts were examined, and 6 articles were selected and assessed for their methodological quality. The retention period after maxillary expansion ranged between 4 weeks and 16 months. Fixed (acrylic plate, Haas, Hyrax and quad-helix) or removable (Hawley and Hawley expander) appliances were used for retention. CONCLUSIONS: Six months of retention with either fixed or removable appliances seem to be enough to avoid relapse or to guarantee minimal changes in a short-term follow-up.