Petrie Cynthia S, Williams John L
Department of Restorative Dentistry, School of Dentistry, University of Missouri-Kansas City, Kansas City, MO 64108, USA.
Clin Oral Implants Res. 2007 Oct;18(5):611-9. doi: 10.1111/j.1600-0501.2007.01384.x. Epub 2007 Jun 21.
The purpose of this study was to examine the influence of variability in bone properties and loading on peri-implant crestal and cancellous bone strains using a probabilistic approach, in combination with finite element (FE) analysis.
Oblique occlusal loading was applied to a single endosseous implant embedded in a two-dimensional (2-D) FE model of a premolar section of a mandible. Perfect bonding was assumed at all interfaces. Five independent parameters (cortical bone thickness (T), cortical (ECORT) and cancellous (ECANC) bone Young's moduli, and vertical (FVERT) and horizontal (FHOR) occlusal forces) were assigned statistical distributions based on data in the literature. Two cancellous bone distribution models were examined, one with a lower mean and range (LM) and the second with a higher mean and range (HM) of cancellous bone Young's modulus values. Sets of randomly chosen values for the five parameters were selected from the distributions and FE analyses were performed for all randomly selected sets.
In the LM model, 50% of the cases experienced hyper-physiologic peri-implant crestal strains in the region of commonly reported saucerization, compared with about 25% of the cases in the HM model. Relative probabilistic sensitivities (%) of bone strains to the independent input parameters (T, ECORT, ECANC, FVERT and FHOR) were as follows: 29, 11, 30, 13, and 17 for the LM model, and 17, 11, 35, 21, and 15 for the HM model, respectively.
Probabilistic analyses of FE models suggest that up to twice as many cases in the LM distribution may be at risk of saucerization as compared with the HM distribution model. Although based on hypothetical distribution values and the limitations inherent to a 2-D analysis, this probabilistic study demonstrated that FE models are very sensitive to the often arbitrarily assigned values for cancellous bone Young's modulus, and also to values used for cortical bone thickness, when the cancellous bone modulus is low.
本研究旨在采用概率方法结合有限元（FE）分析，研究骨特性和负荷变异性对种植体周围嵴顶和松质骨应变的影响。
在下颌前磨牙区二维（2-D）有限元模型中，对单个骨内种植体施加斜向咬合负荷。假定所有界面均为完美结合。根据文献数据，为五个独立参数（皮质骨厚度（T）、皮质（ECORT）和松质（ECANC）骨杨氏模量，以及垂直（FVERT）和水平（FHOR）咬合力量）赋予统计分布。研究了两种松质骨分布模型，一种松质骨杨氏模量值的均值和范围较低（LM），另一种均值和范围较高（HM）。从分布中随机选择五个参数的值集，并对所有随机选择的集进行有限元分析。
在LM模型中，50%的病例在通常报道的骨碟化区域经历了超生理的种植体周围嵴顶应变，而在HM模型中这一比例约为25%。骨应变对独立输入参数（T、ECORT、ECANC、FVERT和FHOR）的相对概率敏感性（%）如下：LM模型分别为29、11、30、13和17，HM模型分别为17、11、35、21和15。
有限元模型的概率分析表明，与HM分布模型相比，LM分布中可能有多达两倍的病例存在骨碟化风险。尽管基于假设的分布值和二维分析固有的局限性，但这项概率研究表明，当松质骨模量较低时，有限元模型对松质骨杨氏模量通常任意指定的值以及皮质骨厚度所使用的值非常敏感。
