Three-Dimensional Evaluation of the Upper Airway Morphological Changes in Growing Patients with Skeletal Class III Malocclusion Treated by Protraction Headgear and Rapid Palatal Expansion: A Comparative Research

Abstract

ObjectiveThe aim of this study was to evaluate the morphological changes of upper airway after protraction headgear and rapid maxillary expansion (PE) treatment in growing patients with Class III malocclusion and maxillary skeletal deficiency compared with untreated Class III patients by cone-beam computed tomography (CBCT).MethodsThirty growing patients who have completed PE therapy were included in PE group. The control group (n = 30) was selected from the growing untreated patients with the same diagnosis. The CBCT scans of the pre-treatment (T1) and post-treatment (T2) of PE group and the control group were collected. Reconstruction and registration of the 3D models of T1 and T2 were completed. By comparing the data obtained from T1, T2 and control group, the morphological changes of the upper airway during the PE treatment were evaluated.ResultsComparing with the data from T1 group, the subspinale (A) of maxilla and the upper incisor (UI) of the T2 group were moved in the anterior direction. The gnathion (Gn) of mandible was moved in the posterior-inferior direction. The displacement of the hyoid bone as well as the length and width of dental arch showed significant difference. The volume and mean cross-sectional area of nasopharynx, velopharynx and glossopharynx region showed significant difference. The largest anteroposterior/the largest lateral (AP/LR) ratios of the velopharynx and glossopharynx were increased, but the AP/LR ratio of the hypopharynx was decreased. In addition, the length and width of the maxillary dental arch, the displacement of the hyoid bone, the volume of nasopharynx and velopharynx, and the AP/LR ratio of the hypopharynx and velopharynx showed significant difference between the data from control and T2 group.ConclusionThe PE treatment of Class Ⅲ malocclusion with maxillary skeletal hypoplasia leads to a significant increase in the volume of nasopharynx and velopharynx.

Three-dimensional analysis of upper airway morphology in skeletal Class III patients with and without mandibular asymmetry

“…[1][2][3][4][5] Previous studies on airway morphology of patients with Class III malocclusion have been focused on the change of airway dimension after treatment with protraction headgear, 6 mandibular setback, 7,8,9 or bimaxillary surgery. 10 Ritcher et al 11 reported two cases of obstructive sleep apnea syndrome found in asymmetrical patients, indicating that upper airway obstruction could exist in patients with mandibular asymmetry.…”

Pharyngeal airway changes following maxillary expansion or protraction: A meta‐analysis

“…The effects of RME or FM on the pharyngeal airway have been repeatedly investigated using various methods, such as cephalometric radiography, computed tomography (CT) and cone beam CT (CBCT), to measure the changes in airway dimensions. However, the study outcomes were inconsistent . Statistically significant dimensional changes in the pharyngeal or nasopharyngeal airway were observed after RME and/or FM treatment in some studies, whereas no significant or limited changes were observed in others .…”

“…In addition, RME and FM were found to exert secondary treatment effects by increasing the pharyngeal airway dimension. However, several studies used only FM, some performed only RME, and other studies conducted FM in combination with RME …”

“…However, the study outcomes were inconsistent . Statistically significant dimensional changes in the pharyngeal or nasopharyngeal airway were observed after RME and/or FM treatment in some studies, whereas no significant or limited changes were observed in others . Among these studies, the major limitations included the lack of untreated controls and long‐term observations, as well as the variation in definition of pharyngeal airways .…”

Computational fluid dynamics simulation of the upper airway response to large incisor retraction in adult class I bimaxillary protrusion patients

“…Many studies have demonstrated that orthodontic treatment causes morphological or functional changes of upper airway34. Therefore, detailed evaluation of the upper airway is essential for orthodontic diagnosis and planning.…”