Abstract
ObjectiveThe purpose of this study was to evaluate the morphological changes of upper airway after Twin Block (TB) treatment in growing patients with Class II division 1 malocclusion and mandibular retrusion compared with untreated Class II patients by cone beam computed tomography (CBCT).Materials and MethodsThirty growing patients who have completed TB treatment were recruited into TB group. The control group (n = 30) was selected from the patients with the same diagnosis and without TB treatment. CBCT scans of the pre-treatment (T1) and post-treatment (T2) data of TB group and control data were collected. After three-dimensional (3D) reconstruction and registration of T1 and T2 data, the morphological changes of upper airway during TB treatment were measured. The statistical differences between T1 and T2 data of TB group as well as T2 and control data were accessed by t-test.ResultsDuring the TB treatment, the mandible moved advanced by 3.52±2.14 mm in the horizontal direction and 3.77±2.10 mm in the vertical direction. The hyoid bone was in a more forward and inferior place. The upper airway showed a significant enlargement in nasopharynx, oropharynx and hypopharynx. In addition, the nasopharynx turned more circular, and the oropharynx became more elliptic in transverse shape. However, the transverse shape of the hypopharynx showed no significant difference. After comparison between T2 and control data, only the horizontal movement of the hyoid bone, the volumetric expansion of the oropharynx and hypopharynx, and changes of the oropharyngeal transverse shape showed significant difference.ConclusionCompared to the untreated Class II patients, the upper airway of growing patients with Class II division 1 malocclusion and mandibular retrusion showed a significant enlargement in the oropharynx and hypopharynx as well as a more elliptic transverse shape in the oropharynx, and the hyoid bone moved to an anterior position after TB treatment.
Highlights
Narrowing of the upper airway has been increasingly recognized as a physiological characteristic in growing patients of Class II division 1 malocclusion with mandibular retrusion [1,2,3]
Compared to the untreated Class II patients, the upper airway of growing patients with Class II division 1 malocclusion and mandibular retrusion showed a significant enlargement in the oropharynx and hypopharynx as well as a more elliptic transverse shape in the oropharynx, and the hyoid bone moved to an anterior position after Twin Block (TB) treatment
Subjects The same selection criteria were used for both TB and control groups: 1) the overjet was at least 7 mm with an Angle Class II molar relationship; 2) SNA angle was within the normal range between 78.4u and 85u; 3) SNB angle was less than 75u, and the patients had a clinically retrognathic mandible which is determined by the soft tissue of the chin being posterior to Bass’ analysis vertical reference line [17]; 4) ANB angle was greater than 4u; 5) the patients had no other potential airway abnormalities
Summary
Narrowing of the upper airway has been increasingly recognized as a physiological characteristic in growing patients of Class II division 1 malocclusion with mandibular retrusion [1,2,3]. The upper airway changes in adult patients with OSA were measured after mandibular repositioning treatment, and showed a significant enlargement in pharyngeal volume [10,11]. The majority of the studies examined the changes of the upper airway through lateral cephalometric radiography. This method limited the accuracy of airway measurement since the two-dimensional (2D) images only allowed an anteroposterior dimension measurement in sagittal plane, and failed to provide a full-scaled view of the upper airway [13]. Retrospective 3D evaluation of the upper airway in growing patients during TB treatment needs to be established
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
