下颌骨材质仿真度对牙种植体有限元分析的影响

发布时间：2018-05-15 13:57

本文选题：牙种植体 + 三维有限元　；参考：《浙江大学》2014年博士论文

【摘要】：有限元分析已广泛地应用于种植牙的生物力学研究。但是,大多数研究是建立在简化的各向同性下颌骨模型上,极少数建立各向异性模型。而下颌骨是一种多相的、非均质的、多孔性、正交各向异性的复合材料。生物力学模型的仿真度会明显影响有限元计算的结果。本研究将基于多模态数据建立高度仿真的完全正交各向异性的下颌骨三维有限元模型(包括高精度牙冠和牙根形态的完整牙列、牙周膜及颞下颌关节结构和主要咀嚼肌群)；系统地比较分析颌骨材质的仿真度(正交各向异性、横观各向同性和各向同性)对种植牙有限元分析的影响；并且利用显微CT扫描建立骨小梁微结构的下颌骨三维有限元模型,比较分析骨小梁结构建模对种植体骨界面力学特性分布的影响。第一部分全牙列高仿真正交各向异性下颌骨三维有限模型的建立目的：建立全牙列高仿真的正交各向异性下颌骨三维有限元模型,为有限元计算结果的准确性提供了充分的保证。材料和方法：选取1名牙列完整的健康男性志愿者,采用螺旋CT和MR扫描下颌骨并以DICOM数据保存。将DICOM数据导入计算机,再结合口腔专用CT扫描的全牙列标准数据,用自主开发的通用外科手术集成系统(Universal Surgical Integration System, USIS)将三组数据配准与融合,最后集成包括皮质骨和松质骨,牙釉质、牙本质、牙周膜、颞下颌关节盘、髁突软骨、颞颌关节窝和关节窝软骨的实体模型。根据带全牙列下颌骨的形态结构和正交各向异性材质主方向的特点,进行网格单元划分,并模拟咀嚼肌加载,建立完全正交各向异性的下颌骨三维有限元模型。结果：建立的下颌骨三维有限元模型包含颞颌关节结构及关节盘、高精度的全牙列结构形态,网格单元形状规则,疏密可控,较密的网格单元分布在颞颌关节接触区和牙冠牙根等力学集中区域。对于颌骨的骨皮质和骨松质区域,每个局部点材质坐标系都用三个正交的主方向确定,每个单元有过渡光滑的局部正交各向异性材质坐标系方向。完整的下颌骨三维有限元模型总共包括497127个节点,334781个四面体网格单元,其中包括40928个膜单元。结论：本实验建立的全牙列正交各向异性下颌骨三维有限元模型,具有很高的生物仿真度,几何相似性和力学相似性极高,为种植牙有限元分析提供了良好的基础。第二部分下颌骨各向异性材质建模对牙种植体有限元分析的影响目的：比较分析正交各向异性、横观各向同性与各向同性下颌骨有限元模型对种植牙有限元分析结果的影响。材料和方法：在USIS软件中,建立包含颞颌关节的全牙列完整下颌骨模型同第一部分。利用光学投影仪和CATIA V软件对Straumann螺纹种植体和基台进行精确三维建模,并植入于下颌骨第一磨牙区。最后分别建成包含种植体的正交各向异性、横观各向同性和各向同性的下颌骨三维有限元模型,导入ANSYS软件进行有限元计算。正交各向异性用9个独立的力学参数来确定,即每个局部点材质坐标系必须三个正交的主方向确定；横观各向同性由等效各向异性推导出5个独立的力学参数来描述,存在一条对称轴,而在垂直于对称轴方向的平面上所有方向都是等效方向；各向同性用2个独立的力学参数来描述。结果：从各向同性到横观各向同性和正交各向异性模型,皮质骨、松质骨、种植体、牙釉质、牙本质和牙周膜等的应力值几乎都以递增为主,但种植体、基台、牙冠、釉质、牙本质和牙周膜等的应力值差别不明显。与各向同性模型相比,下颌骨正交各向异性模型中种植体骨界面的应力应变值几乎都增加,尤其以松质骨应力应变最大值增加最为显著,多则以成倍增加；但正交各向异性模型下颌骨的应力应变分布似乎较均匀,各向同性模型的应力应变集中较明显。结论：种植牙有限元分析时,下颌骨正交各向异性模拟会明显影响种植体骨界面应力和应变的分布,并以增加为主,尤其是松质骨。我们在种植牙生物力学研究中不可忽视下颌骨正交各向异性的力学特性。第三部分骨小梁微结构建模对牙种植体有限元分析的影响目的：利用显微CT扫描建立含种植体的骨小梁微结构下颌骨三维有限元模型,比较分析骨小梁微结构建模对种植体骨界面力学特性分布的影响。材料和方法：拔除健康成年比格犬下颌第三、四前磨牙,术后3月在骨愈合后的牙槽骨植入种植体。植入3月后取含种植体的下颌骨标本,分别用Micro-CT和CBCT扫描,并用USIS软件建立含种植体的骨小梁微结构下颌骨三维有限元模型(精确模型)和宏观结构下颌骨三维有限元模型(简化模型)。最后导入ANSYS软件进行有限元计算,种植体垂直加载50N。结果：考虑骨小梁结构时种植体骨界面应力最大值和平均值都显著增大,应变最大值和平均值都明显减小；等效应力最大值和平均值分别是简化模型的2.6-3.1倍和2.3-3.2倍,而等效应变最大值和平均值分别是简化模型的47%-58%和20%-22%。简化模型中种植体骨界面应力应变集中较明显,应力集中于颈部,应变集中于螺纹部位和底部的松质骨；而骨小梁结构的精确模型中种植体骨界面等效应力应变集中不明显、分布较均匀,应力应变都主要集中在骨小梁。结论：骨小梁结构的精确模型明显影响种植体骨界面应力应变的分布,骨小梁结构有分散应力和缓冲载荷的作用。
[Abstract]:Finite element analysis has been widely applied to the biomechanical study of implant teeth . However , most of the studies have been established on a simplified isotropic mandibular model with a very small number of anisotropic models . The simulation of biomechanical models can significantly affect the results of finite element calculations .
The influence of the simulation degree of jaw materials ( orthogonal anisotropy , transverse isotropic and isotropic ) on the finite element analysis of implant teeth was systematically compared .
The three - dimensional finite element model of the mandible was established by means of micro - CT scanning , and the effects of the structural modeling on the mechanical properties of the implant bone interface were compared .

the first portion

Establishment of Three - dimensional Finite Element Model of Orthotropic Mandible Mandible with Full - tooth Column

Purpose :

A three - dimensional finite element model of orthotropy mandible with full - tooth column height simulation is established , which provides sufficient assurance for the accuracy of finite element calculation .

Materials and methods :

Three groups of data were registered and fused by means of universal Surgical Integration System ( USIS ) , which included cortical bone and cancellous bone , tooth enamel , dentin , periodontal ligament , temporo - mandibular joint disc , condylar cartilage , temporalis joint fossa and articular cartilage .

Results :

The established three - dimensional finite element model of the mandible consists of the structure of the temporo - jaw joint and the articular disc , the high - precision all - tooth column structure , the shape rule of the mesh unit , the density - controllable , the dense mesh unit is distributed in the mechanical concentrated areas such as the temporognathic joint contact zone and the crown root canal .

Conclusion :

The three - dimensional finite element model of all - tooth column orthogonal anisotropy was established in this experiment , which has very high biological simulation , geometric similarity and mechanical similarity , and provides a good basis for the finite element analysis of implant teeth .

the second part

Influence of Modeling of Mandible Anisotropic Materials on Finite Element Analysis of Dental Implants

Purpose :

The effects of orthogonal anisotropy , transverse isotropic and isotropic mandibular finite element model on the results of finite element analysis were compared .

Materials and methods :

In the USIS software , the complete mandible model and the first part of the complete mandible were established . Using the optical projector and the CATIA V software , the Straumann screw implant and abutment were modeled in three dimensions and implanted in the first molar area of the mandible . Finally , three - dimensional finite element model of the mandibular first molar was built . The orthogonal anisotropy was determined by nine independent mechanical parameters , i.e . , each local point material coordinate system must be determined in three orthogonal principal directions ;
The transverse isotropic is described by the equivalent anisotropy of five independent mechanical parameters , and there is an axis of symmetry , and all directions in the plane perpendicular to the axis of symmetry are equivalent directions ;
Isotropic is described by two independent mechanical parameters .

Results :

The stress values of implant , abutment , crown , enamel , dentin and periodontal ligament were almost all increased from isotropic to transverse isotropic and orthogonal anisotropic models , but the stress values of implant , abutment , crown , enamel , dentin and periodontal ligament were not obvious .
However , the stress - strain distribution of the mandible under the orthogonal anisotropic model appears to be more uniform , and the stress - strain concentration of the isotropic model is more obvious .

Conclusion :

In the finite element analysis of implant teeth , the orthogonal anisotropy simulation of mandible can significantly affect the distribution of stress and strain of implant bone interface , especially cancellous bone , and we can not neglect the mechanical properties of mandibular orthogonal anisotropy in implant biomechanical study .

PART III

Effect of Microstructural Modeling on Dental Implant by Finite Element Analysis

Purpose :

The three - dimensional finite element model of bone trabecular structure with implant was established by means of micro - CT scanning , and the effects of microstructure modeling on the mechanical properties of implant bone interface were analyzed .

The mandibular third and four anterior teeth were removed from healthy adult Beagle dogs . The implants were implanted into the alveolar bone after bone healing in March . The mandibular specimens containing implants were scanned by Micro - CT and CBCT respectively . The three - dimensional finite element model ( exact model ) and three - dimensional finite element model ( simplified model ) were established by using the USIS software . Finally , the ANSYS software was introduced to calculate the finite element , and the implant was loaded vertically by 50N .

Results :

When considering the trabecular structure , the maximum stress and the mean value of the implant bone interface were significantly increased , and the maximum strain and the average value were significantly reduced .
The maximum and mean values of equal effect force are 2.6 - 3.1 times and 2.3 - 3.2 times of the simplified model , respectively , while the maximum and average values are 47 % -58 % and 20 % -22 % of the simplified model , respectively .
In the precise model of trabecular structure , the stress strain concentration of implant bone interface is not obvious , the distribution is more uniform , and the stress strain is mainly concentrated in the trabecular bone .

Conclusion :

The precise model of trabecular structure significantly affects the distribution of stress and strain in the implant bone interface , and the trabecular structure has the function of dispersing stress and buffering load .

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：R783.6

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