上颌窦底提升不同高度对种植义齿受力影响的三维有限元分析

Maxillary Sinus Floor Elevation and Implant Biomechanics: A Finite Element Analysis

目的:研究上颌窦底提升后种植义齿修复时,不同提升高度对种植体-骨界面应力状况的影响,为其临床应用提供生物力学参考依据。方法:采用健康志愿者的CT扫描数据,通过Mimics 11.0软件,建立上颌第一磨牙缺失、含上颌窦的上颌骨三维有限元模型,并模拟植入10 mm长标准种植体1枚。模拟上颌骨骨量不足,建立上颌窦底分别提升2、4、6 mm的种植义齿模型,并以无需窦底提升的种植义齿模型为对照。分别从垂直、颊向30°和舌向30°三个方向,对种植义齿上部结构牙冠咬合面中心点施加100 N的集中载荷,用三维有限元分析方法对不同模型的种植体-骨界面进行应力分析。结果:各模型在同一加载条件下,皮质骨的应力最大,松质骨和人工骨的应力值接近。随着窦底提升高度的增高,种植体颈部周围骨组织的应力总体呈先降后升的趋势,在提升高度为4 mm时最小。颊舌向加载时产生的应力远大于垂直载荷下产生的应力。结论:上颌骨后部骨量不足时,上颌窦底提升植骨可以大大改善种植体-骨界面内应力,植骨高度为4 mm时,种植体-骨界面应力总体最小;垂直载荷更有利于种植体-骨界面的应力分布状况,在临床设计种植义齿上部结构时应尽量减小或避免斜向载荷。

Objectives： This study was designed to examine the impact of sinus floor elevation on stress distribution around implants. Methods： CT scanning data were collected from a female volunteer, a 3-dimensional finite element model of maxillary bone with maxillary sinus and without first molar was set up using Mimics 11.0 software. Maxillary sinus floor with limited bone height was computer-simulated. A total of 4 models of the posterior maxilla with implant were computer-simulated by varying the thickness of the grafted bones （ 0, 2, 4, and 6 mm）, 0 mm artificial bone model was as control. Loading of the implants, in 3D, with forces of 100 N in an axial , buccal 30°, and lingual 30° directions respectively. A finite element analysis was performed to examine the stress distribution in the bone surrounding implants. Results： Under the same loading, the maximum yon Mises stresses of cortical bone was the largest, the maximum von Mises stresses of concelous bone was similar to that of artificial bone. To large extent, the maximum yon Mises stresses around implants after the first drop and then rise with the increase of grafted bone heights. 4 mm grafted bone model showed the smallest stress. The maximum yon Mises stresses under axial loading were markedly higher than those under buccal or lingual loadings. Conclusions： From a biomechanical viewpoint, maxillary sinus floor elevation with bone graft can decrease the stress distributions around the implants in the setting of posterior maxillary bone loss, 4 mm grafted bone model showed the smallest stress, axial loading leads to lower strains as compared with oblique loading. In clinical implant design, the oblique loading should be avoided.