| Summary: | 碩士 === 國立臺灣大學 === 臨床牙醫學研究所 === 94 === During the human evolutional process,the bipedal posture was an important and a whole new step. Because of the eyes of human have to view forward, so the cervical vertebra and cranium must adapt for such change. This adaptation will reduce the space between the trunk and the mandible at the same time. Consequently, the kinematic chain of the mandible-head-neck should be influenced. Besides, the developmental changes due to different human head form often concomitant with different mandibular compensation. The compensation appearance might strongly effect the spatial relationship between the trunk and the mandible and then change the kinematic action of the mandible-head-neck kinematic chain. According to the neurophysiological studies that some peripheral proprioceptive mechanisms could strongly regulate the head-neck posture. And a closely organized neurophysiological reflex pattern seemed to be existed between the TNR activity and trigeminal reflex activity. These findings suggest that interaction within the cranio-mandibular-cervical kinematic chains, at least at this neurological level, should exist. About one century ago, the mandibular kinematics was observed that it was composed by condyle rotation and translation. As the optoelectronic recording device was recently developed, the rotation/translation diagrams could be the best presence for accounting mandibular kinematics. The aim of this study was to explore the influences of craniofacial morphology and head-neck posture on the mandibule-head-neck kinematic strategy.
Twenty-three subjects were invited to participate the study(average age was 26 y/o). Every subject was arranged for taking cephalometric films for analyzing the craniofacial parameters. And setting the following six different postures for postures parameters, they are normal posture, half extension, full extension, half flexion, full flexion, and head-neck protrusion. The degree of six head-neck postures were monitored the degrees by using the cervical range of motion instrument. Under the limited motion of head-neck, the subjects were measured the maximum mouth opening between the upper and lower incisal edge by using the ruler with 0.5mm accuracy, under above six head-neck postures. And setting retroreflective maker balls on the head, trunk and mandibular anterior teeth. Using the optoelectronic recording device(Vicon 512) to measure the maximum mouth opening under the above six head-neck postures in the gait-analyzing laboratory. This set up could yield a working volume of 50 x 50 x 50 cm3 with spatial resolution of 0.0008 mm and absolute system measuring error being less than 0.4 mm..
The present results of experiments express that: (1)As the head-neck motion was limited, different head-neck postures and different craniofacial morphology all significantly effect the maxium mouth opening. (2)As the head-neck motion was unlimited, different head-neck postures and different craniofacial morphology all significantly affect the maxium mouth opening. About the craniofacial morphology parameters, the mandibular rotation could explain almost the maximum mouth opening variation, and total mandibular length and the inclination of mandibular ramus could successively enhance the explaining amount of variation. (3)About the rotation/translation diagrams of the mandibular kinematics strategy,it has statistical significance between the extreme head-neck posture and mandibular kinematics strategy after deleting the errors of choosing the reference point by using the differential. And the gonion angle could also be influenced on the mandibular kinematics strategy. (4) As the head-neck motion was unlimited,the head was really to move slightly concomitant with mandibular maximum mouth opening. And the different spaces which existed between the mandible and trunk will show the different grade of head-neck slight moving and have the early or late sequence of motion occurrence.
The conclusion of the present experiments suggests that whatever the motion of head-neck was limited or unlimited, different head-neck posture and craniofacial parameters all affect the mandibular maximum mouth opening and the mandibular condyle kinematics strategy. Therefore, according to our hypothesis, different space between mandibule and trunk was really influenced on the mandibular kinematic strategy.
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