Department of Mechanical Engineering, University of Erlangen-Nuremberg, Erlangen, Germany.
Int J Oral Maxillofac Implants. 2011 Nov-Dec;26(6):1288-95.
Stress caused by a non-passively fitting implant superstructure may induce bone adaptation, thereby changing the magnitude of static implant loading.
In a previous investigation, repeated in vivo strain measurements were conducted on an implant-supported bar to evaluate changes in the magnitude of misfit resulting from bone remodeling processes. Both maximum (445 μm/m) and minimum (383 μm/m) strain values were simulated using a three-dimensional finite element model. The horizontal misfit needed to simulate experimentally determined strain values and the resulting stresses occurring in the restoration and the bone were quantified as von Mises equivalent stress. Additionally, different stages of osseointegration were modeled by altering the elastic modulus of bone immediately surrounding the implants.
To simulate the maximum strain value, a horizontal misfit of 83.3 μm had to be introduced, whereas the minimum strain value could be simulated via a horizontal misfit of 71.5 μm. Maximum misfit caused stress magnitudes of 105 MPa in cortical bone and 5.3 MPa in trabecular bone. Minimum misfit caused stress magnitudes of 90 MPa in cortical bone and 4.6 MPa in trabecular bone. The difference between maximum and minimum horizontal misfit was 12 μm and led to a reduction in maximum stress levels of 15 MPa in cortical bone and 0.7 MPa in trabecular bone. Progressing osseointegration affected the stress situation of the supporting implants.
Within the limitations of this investigation, it can be concluded that bone adaptation may lead to implant site displacement in the range of several micrometers. Early fixation of non-passively fitting superstructures on implants may lead to greater passivity of fit.
非顺应性种植体上部结构引起的应力可能会引发骨适应性反应，从而改变静态种植体负载的大小。
在之前的一项研究中，对种植体支持的杆进行了重复的体内应变测量，以评估骨重塑过程引起的不匹配程度的变化。使用三维有限元模型模拟了最大（445μm/m）和最小（383μm/m）应变值。模拟实验确定的应变值所需的水平不匹配以及在修复体和骨中产生的相应应力通过 von Mises 等效应力进行量化。此外，通过改变种植体周围骨的弹性模量来模拟不同阶段的骨整合。
为了模拟最大应变值，必须引入 83.3μm 的水平不匹配，而最小应变值可以通过 71.5μm 的水平不匹配来模拟。最大不匹配导致皮质骨中的应力值为 105MPa，小梁骨中的应力值为 5.3MPa。最小不匹配导致皮质骨中的应力值为 90MPa，小梁骨中的应力值为 4.6MPa。最大和最小水平不匹配之间的差异为 12μm，导致皮质骨中的最大应力水平降低了 15MPa，小梁骨中的最大应力水平降低了 0.7MPa。骨整合的进展影响了支撑种植体的应力情况。
在本研究的限制范围内，可以得出结论，骨适应性可能导致种植体部位在几个微米的范围内发生位移。早期将非顺应性上部结构固定在种植体上可能会导致更好的顺应性。
