Northeastern University, Department of Mechanical Engineering, Boston, MA 02115, USA.
J Biomech. 2010 Jun 18;43(9):1761-70. doi: 10.1016/j.jbiomech.2010.02.017. Epub 2010 Mar 3.
In this paper the variation of normal and shear stresses along a path defined on the bone-dental implant interface is investigated. In particular, the effects of implant diameter, collar length and slope, body length, and the effects of four different types of external threads on the interfacial stress distribution are studied. The geometry of the bone is digitized from a CT scan of a mandibular incisor and the surrounding bone. The bone and the implant are assumed to be perfectly bonded. The finite element method with 2D plane strain assumption is used to compute interfacial stresses. Highest continuous interfacial stresses are encountered in the region where the implant collar engages the cortical region, and near the apex of the implant in the subcortical region. Stress concentrations in the interfacial stresses occur near the geometric discontinuities on the implant contour, and jumps in stress values occur where the elastic modulus of the bone transitions between the cortical and trabecular bone values. Among the six contour parameters, the slope and the length of the implant collar, and the implant diameter influence the interfacial stress levels the most, and the effects of changing these parameters are significantly noticed only in the cortical bone (alveolar ridge) area. External threads cause significant stress concentrations in interfacial stresses in otherwise smoothly varying regions. This work shows that the presence of external threads could cause significant variations in both normal and shear stresses along the bone-implant interface, but not reduction in shear stress as previously thought.
本文研究了沿骨-种植体界面上定义的路径的正常和剪切应力的变化。特别是，研究了种植体直径、颈圈长度和斜率、体长度以及四种不同类型的外螺纹对界面应力分布的影响。骨的几何形状是从下颌切牙及其周围骨的 CT 扫描中数字化得到的。假设骨和种植体完全结合。使用二维平面应变假设的有限元方法来计算界面应力。在种植体颈圈与皮质区域接合的区域以及在皮质下区域的种植体根尖附近，会遇到最高的连续界面应力。在种植体轮廓的几何不连续处会发生界面应力的应力集中，并且在骨的弹性模量在皮质骨和小梁骨值之间转换的地方会发生应力值的跳跃。在六个轮廓参数中，种植体颈圈的斜率和长度以及种植体直径对界面应力水平的影响最大，仅在皮质骨（牙槽嵴）区域才能明显注意到这些参数变化的影响。外螺纹会导致界面应力中的显著应力集中，即使在平滑变化的区域也是如此。这项工作表明，外螺纹的存在可能会导致沿骨-种植体界面的正常和剪切应力发生显著变化，但不会像以前认为的那样降低剪切应力。
