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Effects of mandibular protrusion on the structural features of the masticatory muscles and upper airway space - a
Daria Madanchi1, Catherine M Paverd2, Constantin von Deuster3
1Clinic of Masticatory Disorders and Dental Biomaterials, Center for Dental Medicine, University of Zurich, Zurich, Switzerland.
Objectives:
Obstructive Sleep Apnea (OSA) is the most common sleep breathing disorder. Treatment of mild to moderate OSA includes mandibular advancement devices (MAD). The varying degrees of mandibular protrusion induced by MADs affect the 3-dimensional arrangement of masticatory muscles. This pilot study aimed to observe the effects of different mandibular protrusions on masticatory muscle features and upper airways in one healthy participant.
Study Design:
Anatomical and diffusion tensor imaging (DTI) magnetic resonance imaging (MRI) scans of the cephalic region of one 24-years-old healthy male subject were obtained with the mandible held stable by a personalized MAD in three positions: habitual bite position (PR=0 mm), middle protrusion (PMID=3.5 mm), maximum protrusion (PMAX=7 mm). Streamline tractography (ST) based on Spherical Deconvolution (SD) was performed. Anatomical masks for the masseter (superficial/deep), medial and lateral pterygoid, and temporalis muscles were manually drawn. The angles formed by each detected muscle fiber projected on coronal, sagittal, and axial planes were computed, and their distribution was calculated. Furthermore, airway volume and minimum cross-sectional area (CSAMIN) for each position were determined.
Results:
ST method captured the fiber orientation of all masticatory muscles. Variations in muscle fiber angles and airway space were observed across mandibular positions. Both airway volume and CSAMIN increased with increasing protrusion.
Conclusions:
Mandibular protrusion affected the orientation and distribution of the masticatory muscle fibers and the upper airway space in the observed subject. These preliminary findings support further investigations into OSA patients.
