A comparison of sagittal and vertical effects between bonded rapid and slow maxillary expansion procedures

The purpose of this study was to determine the vertical and sagittal effect s of bonded rapid maxillary expansion (RME), and bonded slow maxillary expa nsion (SME) procedures, and to compare these effects between the groups. Su bjects with maxillary bilateral crossbites were selected and two treatment groups with 12 patients in each were constructed. The Hyrax screw in the RM E treatment group and the spring of the Minne-Expander in the SME treatment group were embedded in the posterior bite planes, which had a thickness of 1 mm. At the end of active treatment these appliances were worn for retent ion for an additional 3 months. Lateral cephalometric radiographs were take n at the beginning and end of treatment, and at the end of the retention pe riod. The maxilla showed anterior displacement in both groups. The mandible signi ficantly rotated downward and backward only in the RME group. The inter-inc isal angle and overjet increased in both groups. No significant differences were observed for the net changes between the two groups.