Buccal bone plate thickness after rapid maxillary expansion in mixed and permanent dentitions

Introduction: Rapid maxillary expansion (RME) might cause buccal displacement of anchor teeth. Dislocation of teeth outside their alveolar process can damage the periodontium; for this reason, maxillary expansion using deciduous teeth as anchorage in the mixed dentition might be suggested. The aim of this study was to compare changes of buccal bone plate thickness on the maxillary permanent first molars after RME in the mixed and permanent dentitions with different types of anchorage. Methods: Two groups of patients were evaluated with cone- beam computed tomography before and after RME. Group E (21 patients) underwent RME using deciduous teeth as anchorage; group 6 (16 patients) underwent RME using permanent teeth as anchorage. The Wilcoxon test was used to compare changes between the time points in the same groups, and the Mann- Whitney U test was used to compare differences between the groups. Results: In group E, generally, no statistically significant reduction was found in buccal bone plate thickness between the time points. In group 6, most measurements showed significant reductions in buccal bone plate thickness (P <0.05) between the time points, with a maximum decrease of 1.25 mm. Conclusions: RME in the mixed dentition with the appliance anchored to deciduous teeth did not reduce the buccal bone plate thickness of the maxillary permanent first molars, except for the mesial roots on both sides. RME in the permanent dentition caused a reduction of the buccal bone plate thickness of the maxillary permanent first molars when they were used as anchorage in the permanent dentition.