Department of Mechanical Engineering, University of Erlangen-Nuremberg, Glueckstrasse 11, Erlangen, Germany.
Int J Oral Maxillofac Implants. 2010 Sep-Oct;25(5):947-52.
To show, by comparison of horizontal, vertical, and angular misfit in a three-dimensional finite element model, that clinical methods for the evaluation of implant framework fit cannot provide objective results.
Two three-dimensional finite element models were designed for the simulation of experimentally determined strain values of three-unit fixed dental prostheses supported by two implants. Horizontal, vertical, and angular misfits between implants and restorations were used to create predetermined strain levels. The magnitudes of misfit and resulting bone loading were recorded as von Mises equivalent stresses for the different types of misfit.
A horizontal misfit of 36 μm and a vertical misfit of 79 μm had to be modeled to simulate the experimentally determined strain values. An angular misfit of 0.083 degree (equivalent to a gap of 3 μm on one aspect of the implant) resulted in comparable strain levels. Bone loading in the cortical area around both implants ranged from 50 to 90 MPa for horizontal and vertical misfit. In trabecular bone, loading of 2 to 5 MPa was found. For the angular misfit, bone loading up to 20 MPa in the cortical layer and 1 MPa in the cervical part of the trabecular bone occurred at the implant where the misfit had been introduced. Horizontal and vertical misfits led to comparable loading patterns around both supporting implants. Under angular misfit, bone loading mainly occurred around the implant where the misfit had been introduced. Almost no loading was observed in the circumference of the contralateral implant.
Minimal angular misfits between implant abutments and restorations, which cannot be detected clinically, may lead to substantial bone loading.
通过比较三维有限元模型中的水平、垂直和角度不匹配，证明临床评估种植体框架匹配的方法无法提供客观结果。
设计了两个三维有限元模型，以模拟由两个种植体支撑的三单位固定义齿的实验确定的应变值。通过植入物和修复体之间的水平、垂直和角度不匹配来产生预定的应变水平。不同类型不匹配的错位量和由此产生的骨负荷记录为 von Mises 等效应力。
必须模拟 36 μm 的水平不匹配和 79 μm 的垂直不匹配，以模拟实验确定的应变值。0.083 度的角度不匹配（相当于植入物一侧的 3 μm 间隙）导致可比的应变水平。两个种植体周围皮质区的骨负荷范围为水平和垂直不匹配时的 50 至 90 MPa。在小梁骨中，发现负载为 2 至 5 MPa。对于角度不匹配，在引入不匹配的植入物的皮质层中，骨负荷高达 20 MPa，在小梁骨的颈部区域为 1 MPa。水平和垂直不匹配导致两个支撑植入物周围的负载模式相似。在角度不匹配下，骨负荷主要发生在引入不匹配的植入物周围。在对侧植入物的圆周几乎没有观察到负载。
种植体基台和修复体之间无法临床检测到的最小角度不匹配可能导致大量骨负荷。
