CT and finite element analysis of mandibular advancement device mechanics in a participant with obstructive sleep apnea: a proof-of-concept study

BACKGROUND: This study constructed three-dimensional finite element (3D-FE) models of the upper airway and surrounding structures from spiral computed tomography (CT) data. An optimized fluid-structure interaction (FSI) analysis was applied to investigate the biomechanical effects of the mandibular advancement device (MAD) on peri-airway tissues, refining its therapeutic mechanism in obstructive sleep apnea (OSA). METHODS: One adult patient diagnosed with moderate OSA underwent CT scans in natural sleep before and after 2 months of MAD therapy. 3D-FE models of the upper airway and surrounding structures were constructed from CT data to quantify morphological changes and displacements of the hyoid bone, soft palate, tongue, epiglottis, and the upper airway. FSI analysis was performed to assess airflow pressure and velocity in both the sagittal plane and cross-sections of the upper airway, as well as the displacement of the aforementioned soft tissues, at both peak inspiration and expiration. RESULTS: MAD-induced mandibular protrusion resulted in anterosuperior displacement of the tongue, soft palate, epiglottis, and hyoid bone, accompanied by shortening of the soft palate and lengthening of the epiglottis. These alterations dilated the upper airway in both sagittal and coronal dimensions, thereby increasing airway volume and minimum cross-sectional area. MAD also reduced and homogenized airflow pressure and velocity in both the sagittal plane and key cross-sections of the upper airway at peak inspiration and expiration, while attenuating the displacement of the pharyngeal wall, tongue, soft palate, and epiglottis, with effects more pronounced at peak inspiration. CONCLUSIONS: MAD treats OSA through a synergistic biomechanical mechanism. It enlarges the pharyngeal airway via anterosuperior repositioning of peri-airway tissues. This resultant upper airway dilation attenuates and homogenizes airflow pressure and velocity, thereby stabilizing the pharyngeal wall and peripharyngeal structures, with more pronounced effects during inspiration.