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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15mm,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250N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80.62~109.64MPa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5mm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0mm的模型最大应力要略大于下降5mm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5mm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 types of implant-supported mandibular complete denture with denture to study the stress distribution of the implants under different mandibular vertical heights. Methods Mandibular and superior dentures were scanned by cone beam computed tomography (CBCT) to establish the mandibular reference model. The mandibular vertical height of the model was decreased by 0, 5, 10 and 15 mm, respectively. After the implant was assembled, The first six parallel implant supports and the different vertical mandibular implant implant finite element models supported by All-on-four were 6-implant models and 4-implant models, respectively, in two groups (8 One). In the right mandibular first molar central arch static load 250N vertical force, with Ansys 15.0 software for each part of the stress analysis. Results Under the same loading conditions, the maximal implant stress was located on the neck. The maximum stress distribution of 8 models in two groups showed that the maximum stress values of 4-implant group at different vertical mandibular height ranged from 40.12 to 49.06 MPa The maximal stress value of 6-implant group was between 80.62 and 109.64MPa. The maximum stress value of 6-implant group was 2 times that of 4-implant group. The maximal stress of the implants in the two groups showed the lowest when the vertical height of the mandible was reduced by 5 mm. The stress increased with the decrease of the vertical height of the mandible. The maximal stress of the model with 0 mm vertical height was slightly larger than that of the 5 mm lower model. Conclusion The 4-implant and 6-implant-supported edentulous dentures showed no destructive stress on the implant under relatively extreme loading. The 4-implant had a more reasonable stress distribution. The vertical height of the mandible dropped by 5mm The minimum stress, indicating that appropriate to reduce the vertical height is conducive to implant stress distribution more reasonable.