Role of mandibular displacement and airway size in improving breathing after rapid maxillary expansion.

Oral breathing and maxillary deficiency are often associated with steep mandibular plane angle, and retrognathic mandible compared with the faces of healthy controls. Some studies suggested that after rapid maxillary expansion, improvement in nasal breathing and repositioning of mandible with transitory increasing of facial height and, in some cases, spontaneous forward repositioning might occur. The abovementioned mandibular effects could contribute to enlarge oropharynx volume with repositioning of tongue and soft palate with an improvement of upper airway volume after treatment. The aim of this study was to investigate by cone beam computed tomography the role of oropharyngeal volume and mandibular position changes after rapid maxillary expansion in patients showing improved breathing pattern confirmed by polysomnography exam.The final sample of this retrospective study comprised 14 Caucasian patients (mean age 7.6 years) who undergone rapid maxillary expansion with Haas-type expander banded on second deciduous upper molars. Cone beam computed tomography scans and polysomnography exams were collected before placing the appliance (T0) and after 12 months (T1). Mandibular landmarks localization and airway semiautomatic segmentation on cone beam computed tomography scans allowed airway volume computing and measurements.No significant differences were found between oropharyngeal airway changes and mandibular displacement after rapid maxillary expansion in growing patients.The suggested improvement in upper airway and breathing after rapid maxillary expansion should be further related to different compartments of airway such as rhinopharynx and nasal cavity.