Head, neck and trunk movements accompanying jaw tapping

Several studies have examined the functional relationship between mandibula r movement and head or body posture, but head and body motion during jaw mo vement have not been extensively investigated. Ten healthy participants per formed repetitive jaw tapping movement. Piezoelectric accelerometers were a ttached on the surfaces of the participant's forehead, mentum, and over the spinous processes of the sixth cervical, twelfth thoracic and third lumbar vertebrae. The direction in which the antero-posterior acceleration signal s appeared around the onsets of jaw opening and closing were observed for t he period from the 6th to the 25th strokes of the jaw tapping. Around the o nset of jaw opening, the forehead and the lumbar vertebra tended to move po steriorly, but the cervical and thoracic vertebrae moved anteriorly with si gnificant frequencies. The directions of the motions of these locations rev ersed themselves at the beginning of jaw closing; so the motions of the for ehead and the lumbar vertebra were opposed again to the ones of the cervica l and thoracic vertebrae. The results suggest that the head extend-flex mot ion often accompanied the jaw open-close movement, and the motions of the n eck and trunk existed, which would serve the purpose of promoting the mandi ble to move smoothly.