Skeletal and dental changes in the sagittal, vertical, and transverse dimensions after rapid palatal expansion

The purpose of this study was to examine the maxillary and mandibular responses to rapid palatal expansion (RPE) in all 3 dimensions. Twenty children (average age, 11.7 years) who required RPE treatment were included in this study. Pre- (T1) and post-RPE (T2) lateral and posteroanterior (PA) cephalograms and study models were taken for all patients. For each patient, lateral and PA cephalograms at T1 and T2 were traced, and the sagittal, vertical, and transverse measurements were made. In addition, on the pre- and postexpansion models, the widths between the first premolars, the first molars, and the two acrylic halves of the Haas-type expander were measured. Results showed that from T1 to T2, the mean SNA increased 0.35degrees (P <.05) and ANB increased 1.00degrees (P < .05). Both the ANS and PNS moved downward (1.30 mm and 1.43 mm, respectively, P <.05), and the mandibular plane angle (MP-SN) increased 1.72degrees (P <.05). The maxillary and mandibular incisors did not change significantly after RPE. After RPE, the mean increase of maxillary interpremolar width, maxillary intermolar width, maxillary width (J-J), nasal width, and interorbital width were found to be 110.7%, 104.5%, 30.1%, 23.1%, and 3.3% of the screw expansion, respectively. After RPE treatment in children, the maxilla displaced slightly forward and downward (P <.05); the mandible rotated downward and backward, and the anterior facial height increased significantly (P <.05); and the widths of the maxilla and nasal cavity increased significantly (P <.05).