Weijs W A
Dept. Anatomy and Embryology, Academic Centre for Dentistry, Amsterdam, Netherlands.
Acta Morphol Neerl Scand. 1989;27(1-2):149-62.
A review is given of what is known about the functional significance of variation of the morphology of the human mandible and jaw muscles. First, the mandible is a lever transferring muscular forces to the teeth. The angle between corpus and ramus and the width of the ramus are particularly relevant in this respect as they determine the mechanical advantage of the lever system and the capacity for sagittal (open-close) movement. The stability of the mandible in asymmetric bites is especially affected by the ratio between the intermolar and intercondylar distances. The repertoire of bite forces that can be generated at any tooth and the loading pattern of the temporomandibular joint are strongly dependent on the relative size of the masseter, temporalis and medial pterygoid muscles. Second, executing its function as a lever, the mandible is subjected to shearing, bending and torsional forces. The bony parts harbouring the teeth, joints and muscle attachments serve to counter these forces; additional strength is needed in three areas i.e. in the symphysis, the condylar neck and in the transition area between corpus and ramus. In human populations there are clear-cut patterns of correlation between some facial skeletal traits, jaw joint morphology and strength and line of action of the jaw muscles. As a result, facial morphologies can be distinguished with marked differences in mechanical performance of their masticatory apparatus. It is suggested that they emerge as a result of diverging environmental influences during postnatal growth.
本文综述了关于人类下颌骨和颌肌形态变异的功能意义的已知信息。首先，下颌骨是一个将肌肉力量传递到牙齿的杠杆。在这方面，下颌体与下颌支之间的角度以及下颌支的宽度尤为重要，因为它们决定了杠杆系统的机械优势以及矢状（开合）运动的能力。不对称咬合时下颌骨的稳定性尤其受到磨牙间距离与髁突间距离之比的影响。在任何一颗牙齿上能够产生的咬合力范围以及颞下颌关节的负荷模式在很大程度上取决于咬肌、颞肌和翼内肌的相对大小。其次，作为一个杠杆发挥功能时，下颌骨会受到剪切力、弯曲力和扭力。容纳牙齿、关节和肌肉附着点的骨部分用于抵抗这些力；在三个区域即正中联合、髁突颈部以及下颌体与下颌支之间的过渡区域需要额外的强度。在人类群体中，一些面部骨骼特征、颌关节形态与强度以及颌肌的作用线之间存在明显的关联模式。因此，可以区分出咀嚼器官机械性能存在显著差异的面部形态。有人认为，它们是出生后生长过程中不同环境影响的结果。
