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

PLoS One. 2015 Aug 7;10(8):e0135273. doi: 10.1371/journal.pone.0135273. eCollection 2015.

Abstract

Objective: The 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).

Methods: Thirty 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.

Results: Comparing 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.

Conclusion: The PE treatment of Class III malocclusion with maxillary skeletal hypoplasia leads to a significant increase in the volume of nasopharynx and velopharynx.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Child
  • Cone-Beam Computed Tomography
  • Female
  • Humans
  • Image Processing, Computer-Assisted / methods
  • Imaging, Three-Dimensional
  • Male
  • Malocclusion, Angle Class III / diagnosis
  • Malocclusion, Angle Class III / diagnostic imaging*
  • Malocclusion, Angle Class III / therapy*
  • Maxilla / abnormalities*
  • Maxilla / diagnostic imaging
  • Nasopharynx / diagnostic imaging
  • Nasopharynx / physiology
  • Orthodontic Appliances
  • Palatal Expansion Technique*
  • Radiographic Image Interpretation, Computer-Assisted
  • Treatment Outcome

Grants and funding

The study was supported by grants from national natural science foundation of china project (No.11202118), Shandong Science and Technology Planning (Nos. 2007GG3002027, 2010G0020232 and 2010HM053, 2050205) and Shandong University Dental School Project Research (Nos. P2009008, P2009010) of China. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.