The human mandible: lever or link?
The human mandible: lever or link?
复制标题
人类下颌：杠杆还是连杆？
DOI：
--
复制
发表时间：
1975
影响因子：
2.8
通讯作者：
W. Hylander
中科院分区：
文献类型：
--
作者：
W. Hylander
哺乳动物的下颌骨，特别是人类的下颌骨，通常被认为是咬人时的杠杆。然而，这一观念并非没有受到挑战。各种各样的工作者都认为下颌骨并不起杠杆的作用，他们的这一主张基本上基于两个断言：(1)咀嚼肌肉产生的合力总是通过咬点；(2)咬合时，髁突颈和/或颞下颌关节不适合承受反作用力。对肌电图数据和颞下颌关节组织特性的回顾不支持下颌功能的非杠杆假说。此外，对髁突颈部强度的分析表明，该结构足够强大，可以承受杠杆作用期间预期的反作用力。通常人类下颌骨和作用于它的力只在侧面投影中分析。然后通常分析关于下颌髁的力矩；然而，一些工人主张对其他点进行力矩，例如，瞬时旋转中心。显然，选择哪一点是没有区别的，因为在平衡条件下，任何一点的力矩都等于零。分析作用在下颌前突上的力也是有用的，特别是在单侧咬合时。肌电图数据表明，在强大的单侧磨牙咬时，所产生的内收肌力量在咬点和平衡（非咬侧）髁之间传递。因此，为了使这个系统处于平衡状态，必须有一个反作用力作用在平衡髁上。这表明平衡侧的反作用力大于工作侧，这可能解释了为什么患有颞下颌关节疼痛的人通常更喜欢咬患病关节的一侧。
The mammalian mandible, and in particular the human mandible, is generally thought to function as a lever during biting. This notion, however, has not gone unchallenged. Various workers have suggested that the mandible does not function as a lever, and they base this proposition on essentially two assertions: (1) the resultant of the forces produced by the masticatory muscles always passes through the bite point; (2) the condylar neck and/or the temporomandibular joint is unsuited to withstand reaction forces during biting. A review of the electromyographic data and of the properties of the tissues of the temporomandibular joint do not support the non-lever hypothesis of mandibular function. In addition, an analysis of the strength of the condylar neck demonstrates that this structure is strong enough to withstand the expected reaction force during lever action. Ordinarily the human mandible and the forces that act upon it are analyzed solely in the lateral projection. Moments are then usually analyzed about the mandibular condyle; however, some workers have advocated taking moments about other points, e.g., the instantaneous center of rotation. Obviously it makes no difference as to what point is chosen since the moments about any point during equilibrium conditions are equal to zero. It is also useful to analyze the forces acting on the mandible in the frontal projection, particularly during unilateral biting. The electromyographic data suggest that during powerful unilateral molar biting the resultant adductor muscle force is passing between the bite point and the balancing (non-biting side) condyle. Therefore, in order for this system to be in equilibrium there must be a reaction force acting on the balancing condyle. This suggests that reaction forces are larger on the balancing side than on the working side, and possibly explains why individuals with a painful temporomandibular joint usually prefer to bite on the side of the diseased joint.