附着体类型对种植支持可摘局部义齿应力分布的影响

目的：研究种植支持可摘局部义齿修复下颌远中游离端缺失的应力分布，探讨附着体类型对于种植体、各支持组织、义齿以及附着体的应力影响。方法：建立可摘局部义齿修复下颌双侧前磨牙和磨牙缺失的KennedyⅠ类牙列缺损的三维有限元模型，分别为采用传统可摘局部义齿（无种植体）、种植体+Locator附着体+可摘局部义齿、种植体+Magfit磁性附着体+可摘局部义齿进行修复。分析对比各主要成分的应力分布，得到最大von Mises应力值和位移值。结果：建立含有牙体组织、牙周组织以及种植体、附着体、可摘局部义齿的三维有限元模型。有种植体的模型义齿基托下黏骨膜的最大位移量（Locator模型垂直向载荷9.38 μm、斜向载荷45.48 μm，Magfit模型垂直向载荷9.54 μm、斜向载荷39.45 μm）小于没有种植体的RPD（removable partial dentures）模型（模型垂直向载荷95.27 μm，斜向155.70 μm）。Locator和Magfit两种类型的附着体相比较，Locator模型中种植体颈部周围皮质骨的最大应力值大于Magfit模型（Locator模型垂直向载荷10.850 MPa、斜向载荷43.760 MPa，Magfit模型垂直向载荷7.100 MPa、斜向载荷19.260 MPa）。Magfit模型中末端基牙的牙周膜受力更小（Locator模型垂直向载荷0.520 MPa，Magfit模型垂直向载荷0.420 MPa）。结论：在修复下颌KennedyⅠ类牙列缺损时，种植支持可摘局部义齿可减少对末端基牙的扭力，提高义齿稳定性；Locator和Magfit磁性附着体两者对比，Locator附着体水平约束作用更大。

Influence of attachment type on stress distribution of implant-supported removable partial dentures

Objective: To compare influences of different retention attachments on stress among supporting structures .Methods: By 3-dimensional laser scanner and reverse engineering computer aided design ( CAD) software , a basic partially edentulous digital model with mandibular premolar and molar missing was established .Implant attachment and removable partial dentures ( RPD) were added into the basic model to build three kinds of models: RPD only, RPD +implant +Locator attachment , and RPD +implant +Magfit attachment .Vertical and inclined loads were put on artificial teeth unilaterally . By means of 3-dimensional finite element analysis , the stress distribution and displacement of the main supportive structures were compared . Results: A complete 3-dimensional finite element model was established , which contained tooth structure , and periodontal structures .The displacement of the denture was smaller in Locator (9.38μm vertically, 45.48μm obliquely) and Magfit models (9.54μm vertically, 39.45 μm obliquely) compared with non-implant RPD model (95.27 μm vertically, 155.70 μm oblique-ly) .Compared with the two different attachments , cortical bone stress value was higher in Locator model ( Locator model 10.850 MPa vertically , 43.760 MPa obliquely;Magfit model 7.100 MPa vertically , 19.260 MPa obliquely).The stress value of abutment periodontal ligamentin Magfit model (0.420 MPa vertically) was lower than that in Locator model (0.520 MPa vertically).Conclusion:The existence of implant could reduce maximum von Mises value of each supportive structure when Kennedy Ⅰpartially edentulous mandible was restored .Comparing the structure of Magfit and Locator attachment , the contact of Magfit attachment was rigid , while Locator was resilient .Locator attachment could improve stability of the denture dramatical -ly.Locator had stronger effect on defending horizontal movement of the denture .