顱顏面型態與頭頸部姿勢對於下顎-頭頸運動學策略的影響

Abstract

在人類演化學的進程上，雙足站立的姿勢是嶄新且極為重要的步驟。人類於雙足站立後，由於眼睛必須保持向前直視，因此頸椎與頭顱也必須隨著這樣的改變來加以調整，這樣的調整同時會減小身體軀幹與下顎間的空間關係。因此下顎頭頸運動鏈的運動學行為，勢必受到影響。此外，人類因頭型不同所造成發育的改變，伴隨著不同的下顎補償現象，此現象極有可能影響身體軀幹與下顎間的空間關係，進而改變下顎與頭頸運動鏈的運動學行為。根據神經生理學研究，一些周邊本體感受機制可以強烈地調節頭頸部姿勢，而一個密切整合的神經生理反射模式似乎存在於強直的頸部反射作用及三叉反射作用之間，此暗示著至少在神經的層級內，顱下顎頸部運動鏈之間的交互作用應該是存在的。約一個世紀以前，下顎運動學即被觀察出由髁頭的旋轉與位移運動所構成，隨著近年來光電紀錄系統的發展，髁頭旋轉/位移關係圖可被用來作為解釋下顎運動學理想的表現。本實驗的目的旨在探究頭頸部姿勢與顱顏面型態對於下顎頭頸運動策略的影響。 二十三位受測者參與本實驗(平均年齡26歲)，每位受測者被安排拍攝測顱攝影片以分析其顱顏面參數，並設定如下的六種不同頭頸部姿勢做為姿勢的變數，分別為：正常姿勢、一半伸展、全部伸展、一半屈曲、全部屈曲，頭頸前突，此六種頭頸部姿勢之角度由頸部活動範圍量測儀器來監控其角度。受測者於頭頸部活動受限情況下，以精確度達0.5mm之量尺，測量於上述六種姿勢下，上下門齒點最大張口之量測值。另使受測者於頭頸部活動無受限情況下，分別於頭部、軀幹部及下顎門齒點設置反光球標記，於步態分析實驗室中，利用VICON 512紅外線光電系統測量上述六種姿勢下之最大張口量值。該系統能夠建構出一個５０立方公分的工作範圍，量測解析度可達0.0008mm，而最終系統測量之絕對誤差小於0.4mm。 實驗結果顯示：（一）頭頸部運動受限時，不同頭頸部姿勢及不同的顱顏面型態均會明顯地影響下顎最大開口量。(二)當頭頸部無運動受限時，不同的頭頸部姿勢也會影響下顎的最大開口量，以及構成下顎最大開口量的髁關節頭旋轉角度值。而顱顏面型態參數中，下顎髁頭旋轉量可以解釋絕大部份的最大開口量變異數，而總下顎長及下顎支傾斜角度可依次增強此變異數的解釋量。（三）下顎運動學策略旋轉與位移關係圖，經過一次微分以去除參考點選擇的誤差後，極端的頭頸部姿勢對於下顎的運動學策略，有統計學上的差異。而下顎角點角此顏面參數也會影響下顎運動學策略。（四）頭頸部運動無受限時，頭部確實會伴隨著下顎最大張口而微動。且不同的下顎軀幹之間的空間有不同程度的頭頸部微動及運動發生的先後順序。 實驗結論，不論頭頸部是否為運動受限情況，不同的頭頸部姿勢與顱顏面參數皆會影響下顎最大開口量與下顎髁頭運動學策略。因此就我們的假設而言，不同的下顎軀幹之間空間，的確會對下顎運動學策略造成一定程度的影響。

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.