Immediate changes in condylar position after rapid maxillary expansion

Introduction: Although the dentoalveolar and skeletal effects of rapid maxillary expansion are well documented, the condylar response to this procedure is not well understood. The purpose of this study was to test the following null hypothesis: rapid maxillary expansion promotes immediate changes of the position of the condyles in patients with Class I malocclusion. Methods: Thirty-four subjects with Class I malocclusion underwent rapid maxillary expansion. Cone-beam computed tomography images were collected before activation of the expander and 3 weeks later, after screw stabilization. Using specific software functions, it was possible to determine and reproduce head positioning and landmarks during the different times of the study. Results: The axial, coronal, and sagittal planes were examined, and no asymmetries in condylar positions were found at either time. However, statistically significant anterior and inferior displacements of these structures occurred, with respective average values of 0.52 and 0.49 mm. Lateral inclinations of both condyles were observed and confirmed by the coronal condylar angles. Conclusions: The null hypothesis was rejected. Statistically significant anterior and inferior displacements of the condyles occurred. Lateral inclination of the condyles was observed.