两种种植体支持式下颌半口固定义齿种植体应力有限元分析

目的 设计两种种植体支持式下颌半口全牙列固定义齿，研究在不同下颌骨垂直高度降低情况下种植体应力分布情况。方法 利用锥束计算机断层扫描成像（CBCT）扫描下颌骨及上部义齿，形成下颌骨基准模型，将基准模型中下颌骨垂直高度分别下降0、5、10和15 mm，组装种植体后，建立颏孔前6枚平行种植体支持和“All-on-four”支持的不同下颌骨垂直高度的种植体有限元模型，分别为6-种植体模型和4-种植体模型，共两组（8个）。在右下颌第一磨牙中央窝静态加载250 N垂直力，用Ansys 15.0软件进行模型各部分的应力分析。结果 在相同的加载条件下，种植体最大应力值位于颈部；两组8个模型最大应力值分布显示，不同下颌骨垂直高度下4-种植体组的最大应力值在40.12~49.06 MPa之间，6-种植体组的最大应力值在80.62~109.64 MPa之间；6-种植体组的最大应力值是4-种植体组的2倍。两组模型中种植体最大应力在下颌骨垂直高度降低5 mm时均表现为最低，随着下颌骨垂直高度降低，应力逐渐增大，而垂直高度下降0 mm的模型最大应力要略大于下降5 mm模型。结论 4-种植体和6-种植体支持的无牙颌固定义齿在相对极端的载荷下种植体都没有出现破坏性应力，4-种植体有着更加合理的应力分布；下颌骨垂直高度下降5 mm组应力最小，说明适当降低垂直高度有利于种植体应力更加合理的分布。
Objective To design two kinds of fixed full-arch implant-supported prosthesis and to investigate their stress distribution in the different vertical heights of the edentulous mandible. Methods The cone-beam computed tomography(CBCT) scan data of the upper denture and mandible were collected to establish the base models of the mandible. The vertical heights of the mandible models were lowered by 0, 5, 10 and 15 mm, and the three-dimensional finite element models of implants with different vertical heights supported by mental foramen 6 parallel implants and supported by "All-on-Four" were established, including 2 groups (8 models):6-implant group and 4-implant group. A 250 N vertical force was applied to the central fossa of the right mandibular first molar. The stress of each part of the models was analyzed by Ansys 15.0 software. Results Under the same loading condition, the maximum stress value of the implants was in the neck of the implants. The maximum stress distribution of 8 models showed that the maximum stress value was 40.12-49.06 MPa for the 4-implant group and was 80.62-109.64 MPa for the 6-implant group, with the latter being two folds that of the former. In two groups, the maximum stress was the lowest when the vertical height reduction was 5 mm. With the decrease of the mandible vertical height, the stress increased gradually. However, the maximum stress of the 0 mm-height-reduced models was larger than that of 5 mm-height-reduced models. Conclusion There is no destructive stress under certain extreme load in both 4-implant group and 6-implant group, with the 4-implant group having a more reasonable stress distribution. The 5 mm-hight-reduced models have the minimum stress, indicating that appropriate vertical height reduction can lead to more reasonable implant stress distribution