Investigation of cervical muscle mechanisms during jaw movement--using a prototype head-jaw-neck model--.

To explain the pain and dysfunction of neck during jaw movement associated with malocclusion, the physiologic relationships between jaw and cervical movement should be understood. However the complicated reflex effects made it difficult to investigate the biomechanical relationship between the head-neck components. For this reason we have created a model for mechanical system dynamic analysis of the normal stomatognathic system to assess the biomechanics of the cervical movement and muscle activity during jaw movement. We have also statistically validated the model and quantitatively verified the model to the human subject by the amounts and conditions of cervical muscle activity. During jaw opening-closing phases the movement of the model was highly correlated to the subject with an identical movement. However low consistency was achieved during intercuspid phase. These findings indicate the establishment of a valid system, which can be used to evaluate the biomechanical relationships between jaw and cervical movement. Moreover the model verification of cervical muscle activity indicate the mechanical action of jaw can be the primary factor to modify cervical muscles, and cervical muscles coordinate to resist changes in head balance during jaw movement to maintains head posture.