How effective is maxillary expansion as an interceptive treatment in individuals with palatally displaced canines? A systematic review and meta-analysis

Background: The objective was to provide a synthesis of the existing literature on the effectiveness of maxillary expansion in intercepting palatally displaced canines (PDCs).

Methods: Studies that evaluated the effectiveness of maxillary expansion in subjects with PDCs in the mixed dentition period were included. The following electronic databases were searched until November 30, 2021: MEDLINE (via PubMed), Scopus, Google Scholar, Web of Science, and Cochrane library. Grey literature search and manual search were also performed. The risk of bias was assessed using the Cochrane tool for the one randomized controlled trial (RCT) and the ROBINS-I tool for the non-RCTs. The data were extracted and meta-analysis was performed using RevMan 5.4. The Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach was used to assess the certainty of evidence.

Results: Four studies were selected from 9,586 records, which included one RCT and three non-RCTs. The former demonstrated a high risk of bias whereas the non-RCTs showed moderate risk. The meta-analysis of three non-RCTs found no significant improvement in the alpha angle of canines after rapid maxillary expansion, with a difference of -4.26 (95% CI -11.41 to 2.89; P = 0.24). The RCT showed an increase in the eruption rate of high-risk canines with rapid maxillary expansion. Slow maxillary expansion did not demonstrate any favorable change. The level of evidence ranged from low to very low.

Conclusions: There is insufficient evidence to recommend the use of maxillary expansion as a stand-alone procedure in intercepting PDCs. Additional well-conducted trials are required.