Introduction: The purpose of this study was to examine the maxillary response on the transverse dimensions to rapid palatal expansion (RPE) by using cone-beam computed tomography (CBCT).
Methods: Twenty-four children (average age, 9.9 years) who had RPE treatment with a bonded expander were included. Pretreatment orthodontic records (T1) and immediately after expansion (T2) CBCT images were taken for all patients. For each patient, the width of the nasal cavity at the level of the maxillary first permanent molar and second deciduous molar (or second permanent premolar), the width of the maxillary basal bone, and the width of the midpalatal suture at the level of the second deciduous molar (or the second permanent premolar), the first deciduous molar (or first permanent premolar), and the deciduous canine (or permanent canine) at T1 and T2 were measured. In addition, the amount of tipping for both the maxillary right and left first permanent molars was measured.
Results: From T1 to T2, mean increases in nasal width, related to the mean jackscrew opening (8.19 mm), occurred at the levels of the first permanent molars of 33.23% (2.73 mm, P <0.05) and the second deciduous molars of 37.32% (3.06 mm, P <0.05). Significant increases in basal bone of the maxilla were found at all levels (P <0.05), with mean increases of 40.65% (3.33 mm), 44.08% (3.49 mm), 46.73% (3.83 mm), and 46.83% (3.62 mm) of the mean jackscrew opening at the levels of the first permanent molars, and the second deciduous molars, first deciduous molars, and deciduous canines, respectively. Significant openings in the midpalatal sutures was found at all levels (P <0.05), with mean increases of 52.82% (4.33 mm), 53.23% (4.36 mm), 54.35% (4.46 mm), and 52.77% (4.33 mm) of the jackscrew opening at the levels of the first permanent molars, and the second deciduous molars, first deciduous molars, and deciduous canines, respectively. The right first molar tipped buccally an average of 6.2 degrees (P <0.05), and the left first molar tipped buccally 5.6 degrees (P <0.05).
Conclusions: After RPE, significant increases in the transverse dimensions of the nasal cavity, the maxillary basal bone, and the midpalatal suture opening occurred, with the greatest increase in the midpalatal suture followed by basal bone and nasal cavity. The midpalatal suture opened in a parallel fashion. Moreover, significant buccal tipping occurred on both maxillary first molars.
Copyright 2010 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.