Influence of Experimentally Deviated Mandibular Position on Static Standing Posture.

Background: The purpose of this study was to investigate changes in six segments in the head, jaw, torso, pelvis, and bilateral shanks, the ground reaction force vectors of each foot and the center of mass in the static standing posture induced by an experimental mandibular deviated splint. Methods: Ten healthy adults with no past medical history related to the stomatognathic system or otological disease participated in this study. Measurements were performed by motion capture (Vicon Nexus, Vicon) and tw o ground reaction force meters. We employed a three-dimensional motion analysis software (Visual 3D, c-Motion), and added the jaw model to the musculo-skeletal model disclosed by the International Society of Biomechanics. Results: Compared to those in the mandibular rest position, the center of gravity of the five segments and the center of mass were shifted leftward (mandibular deviated direction) at the mandibular deviated position, confirming that the shift was larger in the upper regions. Additionally, rotations in retroflexion, the left rotation of the jaw segment, and rotation in left lateroflexion at the right shank segment were observed. In the ground reaction forces, vertical components were shifted leftward. Moments in the Y component at the left ankle and right hip were significantly changed. Conclusion: The experimentally deviated mandibular position made the jaw segment itself shift leftward significantly. This mandibular deviation made the head shift significantly followed by larger effects in the more upper segments. Therefore, abnormalities of occlusal position affect the static standing posture. [ABSTRACT FROM AUTHOR]