Zhang F, Langenbach G E, Hannam A G, Herring S W
Department of Oral Health Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, Canada.
J Dent Res. 2001 Jan;80(1):327-35. doi: 10.1177/00220345010800010601.
Specification of mass properties is an essential step in the modeling of jaw dynamics, but obtaining them can be difficult. Here, we used three-dimensional computed tomography (CT) to estimate jaw mass, mean bone density, anatomical locations of the mass and geometric centers, and moments of inertia in the pig jaw. High-resolution CT scans were performed at one-mm slice intervals on specimens submerged in water. The mean estimated jaw mass was 12% greater than the mean wet weight, and 33% more than the mean dry weight. Putative bone marrow accounted for an extra 13% of mass. There was a positive correlation between estimated mean bone density and age. The mass center was consistently in the midline, near the last molar. The mean distance between the mass center and geometric center was small, especially when bone marrow was taken into account (0.58 +/- 0.21 mm), suggesting that mass distribution in the pig jaw is almost symmetrical with respect to its geometric center. The largest moment of inertia occurred around each mandible's supero-inferior axis, and the smallest around its antero-posterior axis. Bone marrow contributed an extra 9% to the moments of inertia in all three axes. Linear relationships were found between the actual mass and a mass descriptor (product of the bounding volume and mean bone density), and between the moments of inertia and moments of inertia descriptors (products of the mass descriptor and two orthogonal dimensions forming the bounding box). The study suggests that imaging modalities revealing three-dimensional jaw shape may be adequate for estimating the bone mass properties in pigs.
质量属性的确定是颌骨动力学建模中的关键步骤，但获取这些属性可能具有挑战性。在此，我们使用三维计算机断层扫描（CT）来估计猪颌骨的质量、平均骨密度、质量和几何中心的解剖位置以及惯性矩。对浸没在水中的标本以1毫米的切片间隔进行高分辨率CT扫描。估计的颌骨平均质量比平均湿重大12%，比平均干重大33%。假定的骨髓占额外的13%质量。估计的平均骨密度与年龄之间存在正相关。质心始终位于中线，靠近最后一颗磨牙。质心与几何中心之间的平均距离较小，尤其是考虑骨髓时（0.58±0.21毫米），这表明猪颌骨中的质量分布相对于其几何中心几乎是对称的。最大惯性矩出现在每个下颌骨的上下轴周围，最小惯性矩出现在其前后轴周围。骨髓在所有三个轴上对惯性矩的贡献额外增加了9%。在实际质量与质量描述符（边界体积与平均骨密度的乘积）之间，以及惯性矩与惯性矩描述符（质量描述符与形成边界框的两个正交维度的乘积）之间发现了线性关系。该研究表明，揭示三维颌骨形状的成像方式可能足以估计猪的骨质量属性。
