Clinical effect on the alveolar bone of maxillary molar after rapid maxillary expansion: a systematic review and meta-analysis

Abstract Background This study assessed the effects of rapid maxillary expansion (RME) on alveolar bone cortical thickness and vertical bone level of maxillary first molar. Material and methods PubMed, Web of Science, Cochrane Central Register of Controlled Trials (CENTRAL), Scopus and a manual search in reference lists of the included studies were searched up to November 2020. The data extraction and risk of bias assessment were performed independently by two authors. Review Manager 5 was used for quantitative analysis. Results Eight studies were selected for the systematic review, and six studies were statistically selected in meta-analysis. The thickness of the distal buccal alveolar bone was significantly reduced of both left (MD 0.53;95% CI:0.15–0.90) and right (MD 0.61;95% CI:0.28–0.94) sides of the maxillary first molar after RME. The same was true for the left (MD 0.63;95% CI:0.28–0.98) and right (MD 0.63;95% CI:0.36–0.91) sides of the mesial buccal side. And the vertical distance between the cusp tip and the buccal alveolar crest increased significantly after RME (SMD − 0.92;95% CI: -1.20–0.64). However, the study of palatal cortical thickness of maxillary first molar needs more clinical trials because of its high heterogeneity (left: I2 = 92%; right: I2 = 86%). Conclusions According to current studies, RME can reduce the buccal cortical thickness of maxillary first molars and increase vertical bone loss. More research is needed to determine the stability of the results. However, it is advisable to evaluate the alveolar bone before treatment.