Three-Dimensional Computed Tomography Analysis of Airway Volume Changes Between Open and Closed Jaw Positions

Abstract

Introduction Airway dimensions are closely linked to the bone and soft-tissue craniofacial anatomy. Reduction of the airway is seen with airway disorders and can impair function. The purpose of this retrospective study was to determine whether changing from open to closed jaw position affects the volume of the nasal cavity, nasopharynx, and oropharynx; the soft palate; the soft-tissue thickness of the airway; and the most constricted area of the airway. Methods Following reliability studies, in this retrospective study, we analyzed cone-beam computed tomography scans taken in both closed and open jaw positions of 60 subjects who were undergoing diagnosis and treatment of temporomandibular disorders. On each scan, condyle-fossa measurements, volumes of airway segments (nasal cavity, nasopharynx, oropharynx), soft palate areas, soft tissue thicknesses of the airway, and the most constricted area of the airway and its location were measured using Dolphin imaging software (version 11.5; Patterson Dental Supply, Chatsworth, Calif). Differences between the 2 jaw positions were analyzed with paired t tests, accepting P ≤0.05 as significant. Results Significant changes in airway dimensions were found between the closed and open jaw positions. With jaw opening, the nasopharynx volume increased, whereas the oropharynx volume decreased. Significant decreases were also found for measurements of basion to posterior airway wall, cervical vertebrae to posterior airway wall, most constricted area, nasal cavity volume, and soft palate area when the jaw was open. Conclusions Changing jaw position significantly affects airway dimensions.