Introduction: The orthopedic treatment for Class III malocclusion increase the upper airway space in children and young adolescents. Cone-beam computed tomography (CBCT) have been widely used to assess the upper airway due the adequate accuracy and possibility of tridimensional appraisal. Objective: This randomized clinical trial aims to compare the airway volume and shape after orthopedic maxillary protraction using two different protocols. Methods: The experimental group is composed by 20 patients with a mean initial age of 10 years and two months old (8 females and 12 males) treated with miniscrew anchored maxillary protraction. In this group, miniscrew anchored rapid palatal expansion (MARPE) was used in the maxilla and two miniscrews at the distal aspect of permanent canines were placed in the mandible. Class III elastics were used full-time for one year. The control group is composed by 15 patients with a mean initial age of 10 years and seven months old (9 males and 6 females) treated with a Hyrax expander and two miniscrews in the distal aspect of mandibular canines. Class III elastics were used similarly to the experimental. CBCT with 13cm-FOV and 0.25mm voxel size was obtained before (T1) and after 12 months of therapy (T2). The sample was treated from June 2017 to June of 2019 in Bauru Dental School, University of São Paulo. Data analyses will be performed at Case Western Reserve University, Cleveland, Ohio, USA. Using Dolphin software, minimum cross-sectional area, total upper airway volume, nasopharyngeal airway volume, oropharyngeal airway volume and hypopharyngeal airway volume will be evaluated. Open-source softwares (ITK-SNAP and 3D slicer) will be used for performing airway segmentations and volume measurements. 3-D color maps and semitransparency overlays of the airway will be acquired. Shape analysis of the T1 and T2 superimposed airways will be obtained using the SPHARM-PDM tool in the 3D Slicer software. The paired t test will be used for intragroup comparisons. Independent t test will be used for intergroup comparisons. A significance level of 5% will be regarded for all tests.
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