Elastic properties and masticatory bone stress in the macaque mandible
Elastic properties and masticatory bone stress in the macaque mandible
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DOI：
10.1002/1096-8644(200008)112:4
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发表时间：
2000-08-01
影响因子：
2.8
通讯作者：
Hylander, WL
中科院分区：
文献类型：
--
作者：
Dechow, PC;Hylander, WL
用应变片进行力学分析的一个重要局限性是很难从应变测量值直接估计骨骼元件中的应力或载荷模式。由于皮质骨固有的各向异性，主应变和主应力的方向不一定一致，理论上已经证明这种差异可能高达45度（Cowin和哈特，1990）。同样，应力和应变大小的相对比例可能不同。本研究测量了猕猴下颌骨下缘颊面和舌面皮质骨区域的弹性特性，然后将弹性特性数据与已发表的猕猴下颌骨应变数据和一种新的在体应变计实验相结合，以确定最大和最小主应力的方向和大小。目的是比较应力和应变，并评估它们之间的方向和相对大小的差异。主要的问题是这些差异是否会导致对下颌功能的不同解释。弹性模量和剪切模量，泊松比测定使用超声波技术从颊和舌皮质表面在12猕猴下颌骨。下颌骨应变计数据来自一组已发表的实验（Hylander，1979）和一项新实验，在该实验中，将玫瑰花形应变计固定在成年雌性食蟹猴下颌体的颊侧和舌侧皮质上，然后记录咀嚼期间的骨应变。将平均弹性特性与应变数据结合起来计算下颌体的应力估计，弹性特性与人类下颌皮质的弹性特性相似。在其下边缘附近，猕猴下颌骨在纵向方向上最僵硬，在上下方向上不太僵硬，在垂直于骨表面的方向上最不僵硬。下颌骨的舌面比颊面稍硬。从平均应变计算的应力的大小范围从-16.00 GPa的压缩应力到8.84 GPa的拉伸应力。主应力的方向取决于应变片位置是在工作侧还是平衡侧。在下颌骨的平衡侧，最大主应力几乎垂直于下颌骨的下缘。在下颌骨的工作侧，最大主应力的方向比平衡侧更易变，表明可能的加载机制范围更大。在下颌骨下缘附近，应力和应变的方向差为12度或更小，与最大和最小应变之间的比值相比，最大和最小应力之间的比值更偏离1.0的比值。结果并没有提供任何重大的重新解释猕猴下颌骨功能，而是确认和扩展现有的工作。下颌骨平衡侧的应力和应变之间的差异通常支持以下观点：在动力冲程期间，下颌骨在咀嚼和换能器咬合期间弯曲并轻微扭曲。计算出的应力用来削弱扭转的相对重要性。在工作侧，与应变分析相比，应力分析的变化范围更大，这表明在每个单独的实验中对载荷和应力模式进行更详细的检查将有助于解释结果。但在许多实验中，需要更多的信息来解释其他叠加的区域负荷模式，这可能包括平行弯曲和反向平行弯曲。(C)2000 Wiley-Liss，Inc.
One important limitation of mechanical analyses with strain gages is the difficulty in directly estimating patterns of stress or loading in skeletal elements from strain measurements. Because of the inherent anisotropy in cortical bone, orientation of principal strains and stresses do not necessarily coincide, and it has been demonstrated theoretically that such differences may be as great as 45 degrees (Cowin and Hart, 1990). Likewise, relative proportions of stress and strain magnitudes may differ. This investigation measured the elastic properties of a region of cortical bone on both the buccal and lingual surfaces of the lower border of the macaque mandible, The elastic property data was then combined with macaque mandibular strain data from published and a new in vivo strain gage experiment to determine directions and magnitudes of maximum and minimum principal stresses. The goal was to compare the stresses and strains and assess the differences in orientation and relative magnitude between them. The main question was whether these differences might lead to different interpretations of mandibular function. Elastic and shear moduli, and Poisson's ratios were measured using an ultrasonic technique from buccal and lingual cortical surfaces in 12 macaque mandibles. Mandibular strain gage data were taken from a published set of experiments (Hylander, 1979), and from a new experiment in which rosette strain gauges were fixed to the buccal and lingual cortices of the mandibular corpus of an adult female Macaca fascicularis, after which bone strain was recorded during mastication. Averaged elastic properties were combined with strain data to calculate an estimate of stresses in the mandibular corpus, The elastic properties were similar to those of the human mandibular cortex. Near its lower border, the macaque mandible was most stiff in a longitudinal direction, less stiff in an inferosuperior direction, and least stiff in a direction normal to the bone's surface. The lingual aspect of the mandible was slightly stiffer than the buccal aspect. Magnitudes of stresses calculated from average strains ranged from a compressive stress of - 16.00 GPa to a tensile stress of 8.84 GPa. The orientation of the principal stresses depended on whether the strain gage site was on the working or balancing side. On the balancing side of the mandibles, maximum principal stresses were oriented nearly perpendicular to the lower border of the mandible. On the working side of the mandibles, the orientation of the maximum principal stresses was more variable than on the balancing side, indicating a larger range of possible mechanisms of loading. Near the lower border of the mandible, differences between the orientation of stresses and strains were 12 degrees or less. Compared to ratios between maximum and minimum strains, ratios between maximum and minimum stresses were more divergent from a ratio of 1.0. Results did not provide any major reinterpretations of mandibular function in macaques, but rather confirmed and extended existing work. The differences between stresses and strains on the balancing side of the mandible generally supported the view that; during the power stroke the mandible was bent and slightly twisted both during mastication and transducer biting. The calculated stresses served to de-emphasize the relative importance of torsion. On the working side, the greater range of variability in the stress analysis compared to the strain analysis suggested that a more detailed examination of loadings and stress patterns in each individual experiment would be useful to interpret the results.Torsion was evident on the working side; but in a number of experiments, further information was needed to interpret other superimposed regional loading patterns, which may have included parasagittal bending and reverse parasagittal bending. (C) 2000 Wiley-Liss, Inc.