Computed Tomographic Evaluation of Three-dimensional Changes in Pharyngeal Airway in Class II Division 1 Patients

Objective: Recent years have witnessed a renewed interest to determine a quantifiable relationship between mandibular advancement performed with an orthodontic appliance and the resulting airway dimensions and volume. The study was conducted to evaluate the changes in dimensions of pharyngeal airway space using computed tomography (CT) in Class II division 1 patients with retrognathic mandible treated by twin block appliance and to compare them with untreated controls. Materials and methods: Twenty-five patients with Class II division 1 malocclusion of age group 9 to 15 years were selected randomly and evaluated for changes in pharyngeal airway dimensions with and without twin block. Patients in each group underwent CT scan of head and neck region at pretreatment stage and 6 months after the initial scan. Institutional approval for the project was obtained from the ethical committee. Volume, area, transverse and anterioposterior (AP) dimensions of upper (oropharynx) and lower (hypopharynx) pharyngeal airways were measured on scanogram using computer software and intragroup as well as intergroup comparisons were done. Results: There was a statistically significant increase in the volume of both hypopharynx and oropharynx in patients treated with twin block. Area, transverse and AP dimensions of oropharynx also increased significantly. In hypopharynx, area and transverse dimensions increased markedly but no increase in AP dimension was observed. Three-dimensional (3D) reconstruction of the airway also demonstrates a considerable increase in pharyngeal airway space. Conclusion: Twin block can be a promising appliance for improving pharyngeal airway space in Class II division 1 patients with retrognathic mandible. However, the long-term implications of this treatment modality needs further consideration and a longer period of follow-up.