STRESS AND STRAIN IN THE MANDIBULAR SYMPHYSIS OF PRIMATES - A TEST OF COMPETING HYPOTHESES
STRESS AND STRAIN IN THE MANDIBULAR SYMPHYSIS OF PRIMATES - A TEST OF COMPETING HYPOTHESES
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DOI：
10.1002/ajpa.1330640102
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发表时间：
1984-01-01
影响因子：
2.8
通讯作者：
HYLANDER, WL
中科院分区：
文献类型：
--
作者：
HYLANDER, WL
本研究的主要目的是检验灵长类动物联合应激的各种假说。首先，这些模式的联合应变，将与各种假设模式的联合应力制定。然后，通过将公式化的骨应变模式与实际的体内联合骨应变模式进行比较，对这些假设的应力和应变模式进行测试。在6只成年食蟹猴（Macacafascicularis）的耻骨联合唇侧中下三分之一的中线上粘贴玫瑰花形和/或单元件应变片，测定了活体耻骨联合骨应变的模式。从麻醉中恢复后，在咀嚼、切开和等长咬合期间记录骨应变。在打哈欠、舔和威胁行为中也记录了联合骨应变。在咀嚼的动力冲程期间，猕猴联合明显地主要被背腹侧地剪切和/或围绕横轴扭转并且通过下颌体的侧向横向弯曲而弯曲。在下颌体横向弯曲过程中，猕猴联合的唇侧受到压缩弯曲应力，而舌侧受到拉伸弯曲应力。在咀嚼的开启行程和其他开颌行为中，猕猴的下颌体内侧横向弯曲使联合弯曲。此时，联合的唇侧经历拉伸弯曲应力，而其舌侧经历压缩弯曲应力。在咀嚼的动力和张开冲程期间，猕猴下颌骨在其曲率平面内弯曲，因此下颌骨充当弯曲梁。这一点很重要，因为它会导致猕猴联合舌侧沿着的应力水平升高，特别是在咀嚼的动力冲程期间。在切开的动力冲程期间，咬合力的局部影响尚不清楚;然而，此时猕猴联合的下半部分由于下颌体绕其长轴扭转而被背腹剪切和弯曲。这种应力分析的结果对理解联合结构的力学属性具有意义。为了抵抗背腹侧剪切，最重要的联合属性是在施加应力的平面内具有足够的骨横截面积。相比之下，骨的横截面积和联合形状对于在联合扭转和3种联合弯曲状态下有效对抗应力都很重要。对抗由于下颌体绕其长轴扭转而引起的联合弯曲的有效方法是增加联合的垂直高度或通过使骨沿着联合的下侧面集中而形成不对称的梁截面，例如，形成了一个猿类大陆架对抗由于下颌体的内侧或外侧横向弯曲而引起的关于横轴的联合扭转和联合弯曲的有效方法是增加联合的唇-舌厚度，例如，形成一个上级横向圆枕。
The primary purpose of this study was to test various hypotheses about symphyseal stress in primates. First, those patterns of symphyseal strain that would be associated with various hypothetical patterns of symphyseal stress were formulated. Then these hypothetical patterns of stress and strain were tested by comparing the formulated bone strain pattern with actual in vivo symphyseal bone strain patterns. Patterns of in vivo symphyseal bone strain were determined by bonding rosette and/or single-element strain gauges to the midline of the middle and lower third of the labial aspect of the symphysis of 6 adult Macaca fascicularis. Following recovery from the anesthetic, bone strain was recorded during mastication, incision and isometric biting. Symphyseal bone strain was also recorded during yawning, licking and threat behaviors. During the power stroke of mastication, the macaque symphysis is apparently predominately sheared dorsoventrally and/or twisted about a transverse axis and bent by lateral transverse bending of the mandibular corpora. During lateral transverse bending of the mandibular corpora, the labial aspect of the macaque symphysis experiences compressive bending stress, while the lingual aspect experiences tensile bending stess. During the opening stroke of mastication and during other jaw opening behaviors, the macaque symphysis is bent by medial transverse bending of the mandibular corpora. At this time the labial aspect of the symphysis experiences tensile bending stress, while its lingual aspect experiences compressive bending stress. During both the power and opening strokes of mastication, the macaque mandible is bent in the plane of its curvature, and therefore the mandible acts as a curved beam. This is important because it results in elevated levels of stress along the lingual aspect of the macaque symphysis, particularly during the power stroke of mastication. During the power stroke of incision, the local effects of the bite force are unknown; however, at this time the lower half of the macaque symphysis is both sheared dorsoventrally and bent due to twisting of the mandibular corpora about their long axes. The results of this stress analysis have implications for understanding the mechanical attributes of symphyseal structure. In order to counter dorsoventral shear, the most important symphyseal attribute is to have adequate cross-sectional area of bone in the plane of the applied stress. In contrast, both the cross-sectional area of bone and symphyseal shape is important in order to counter stress effectively during symphyseal torsion and the 3 symphyseal bending regimes. An effective way to counter symphyseal bending due to twisting of the mandibular corpora about their long axes is to either increase the vertical height of the symphysis or to form an asymmetrical beam section by concentrating bone along the lower aspect of the symphysis, e.g., forming a simian shelf. An effective way to counter symphyseal torsion about a transverse axis and symphyseal bending due to medial or lateral transverse bending of the mandibular corpora is to increase the labio-lingual thickness of the symphysis, e.g., forming a superior transverse torus.