Hyoid bone position and orientation in Class I and Class III malocclusions.

Various studies have documented a variability of hyoid bone position in relation to changed mandibular position or head posture. The aim of this study was to investigate the hyoid bone position and inclination on the cephalometric radiographs of two groups of patients exhibiting Class I and Class III malocclusions. The radiographs were taken in both centric occlusion and wide-opened mandibular position, and 17 measurements were performed on both tracings. The findings reveal a statistically significant difference in the position and inclination of the hyoid bone in the two groups; Class III patients, especially the boys, show a more anterior position of the hyoid bone and also a reverse inclination. This might have an implication on the function of the suprahyoid and infrahyoid muscles and thus on the direction of mandibular growth.