Karl Matthias, Winter Werner, Taylor Thomas D, Heckmann Siegfried M
Department of Prosthodontics, School of Dental Medicine, University of Erlangen-Nuremberg, Germany.
Int J Oral Maxillofac Implants. 2006 Sep-Oct;21(5):756-62.
It is believed that implant-supported fixed partial dentures (FPDs) should display passive fit. The objective of this in vivo-based finite element analysis (FEA) was to quantify the magnitude of bone loading occurring on account of the fixation of cemented or screw-retained 5-unit superstructures.
Based on a patient situation with 3 implants, 4 different groups of restorations with 10 samples each were fabricated. Strain gauges on the pontics of the restorations were used for in vivo measurements. Using the values obtained, bone loading in 3-dimensional FE models was simulated as von Mises equivalent stress.
The in vivo measured mean strain values ranged from 32 microm/m to 458 microm/m at the different sites. FEA revealed stresses between 5 and 30 MPa in the cortical area, while in trabecular bone values ranging from 2 MPa to 5 MPa were observed. Stress of a similar magnitude was found for axial implant loading with 200 N.
Assuming that the axial loading of a single implant with 200 N is within the realm of the bone's adaptation ability, it would appear that the amount of stress resulting from the fixation of superstructures alone does not constitute a risk.
The level of precision of fit which can be obtained in superstructure fabrication would appear to suffice to produce restorations that do not cause bone damage.
人们认为种植体支持的固定局部义齿（FPDs）应呈现被动就位。这项基于体内的有限元分析（FEA）的目的是量化由于粘结或螺丝固位的5单位上部结构固定而产生的骨负荷大小。
基于一名有3颗种植体的患者情况，制作了4组不同的修复体，每组10个样本。修复体桥体上的应变片用于体内测量。利用获得的值，在三维有限元模型中将骨负荷模拟为冯·米塞斯等效应力。
体内测量的不同部位平均应变值范围为32微米/米至458微米/米。有限元分析显示皮质区域应力在5至30兆帕之间，而在松质骨中观察到的值范围为2兆帕至5兆帕。在200牛的种植体轴向加载时发现了类似大小的应力。
假设单个种植体200牛的轴向加载在骨的适应能力范围内，那么仅由上部结构固定产生的应力大小似乎不构成风险。
在上部结构制作中能够获得的就位精度水平似乎足以生产出不会导致骨损伤的修复体。
