牙合垫治疗对深覆牙合的TMD患者颞下颌关节应力分布影响的有限元分析

发布时间：2018-04-03 18:39

本文选题：牙合垫　切入点：深覆牙合　出处：《山东大学》2014年博士论文

【摘要】：研究背景颞下颌关节紊乱病(temporomandibular joint disorders, TMD)是口腔颌面部常见的疾病之一。颞下颌关节紊乱病的病因非常复杂,咬合异常病因学说在颞下颌关节紊乱病中占有非常重要的地位。许多异常的咬合因素,比如深覆牙合、第三磨牙过长、部分后牙的反牙合、牙合干扰等等都曾经被报道过与颞下颌关节紊乱病的病因有关。其中深覆牙合能够影响咀嚼运动和肌电活动,与颞下颌关节紊乱病的发生密切相关,有研究显示深覆牙合的患者出现颞下颌关节紊乱病的几率是正常人的13.2倍。颞下颌关节紊乱病的治疗方法很多,如各种药物治疗,各种物理治疗,各种牙合治疗包括各种牙合垫等。颞下颌关节紊乱病的治疗原则是首选可逆性的治疗方法,比如说通过牙合垫来做牙合间矫治。随着近些年来各个学科之间交流的日益广泛,在力学研究中应用的有限元分析方法(Finite Element Method, FEM)已经被广泛应用到了医学领域。Friedenberg在1969年第一次将有限元分析方法应用于医学领域。Thresher和Farah于1973年将二维有限元分析方法引入到了口腔医学领域。目前有限元分析方法应用的范围已经涉及到口腔医学的各个领域。三维有限元法已被广泛应用到单个牙齿、牙周膜、牙槽骨、桩核冠、可摘局部义齿、固定义齿、种植义齿、全口义齿及颞下颌关节的应力分析。但是,对于深覆牙合的颞下颌关节紊乱病患者,运用三维有限元分析方法对其进行牙合治疗前后的的颞下颌关节进行受力分析,还未见相关报道。研究目的本研究就是通过建立深覆牙合颞下颌关节紊乱病患者的颞下颌关节以及下颌骨的三维有限元模型,分别在牙合垫治疗前牙合垫治疗后进行加载并分析颞下颌关节以及下颌骨的应力分布情况,以便更好地深入研究颞下颌关节紊乱病患者的髁状突、关节窝和关节盘以及与下颌骨之间的生物力学关系,为临床设计提供生物力学参考依据。材料与方法 1颞下颌关节以及下颌骨的三维CAD (Computer Aided Design,计算机辅助设计)模型的建立和处理 1.1建模素材选择一名24岁的深覆牙合颞下颌关节紊乱病患者作为志愿者,通过戴用牙合来治疗颞下颌关节紊乱病。治疗前后分别行双源CT扫描,获得颞下颌关节区的影像资料。 1.2双源CT扫描扫描的范围自颅骨上方至下颌骨下缘,根据需要选择性重建薄层图像,扫描参数为扫描层厚0.6mm,重建间隔0.3mm,窗宽1500,窗位450,球管电压为120kv。扫描完成后将获得的扫描影像数据以DICOM格式存储。 1.3图像处理将上述文件导入软件Mimics当中,利用其中的分割工具将需要的目标区域边界提取出来,完成几何模型的建立。 1.4颞下颌关节盘CAD模型的提取借助Magics12.0软件,从下颌骨髁状突的关节面选取与关节盘匹配的位置区域生成厚度约为2.0mm厚的关节盘原始形状,将原始形状的关节盘与下颌骨模型进行布尔运算,即可得到颞下颌关节盘的CAD模型。 2颞下颌关节以及下颌骨的三维有限元模型的建立和处理 2.1三维有限元模型的生成采用软件MSC.Marc2005中Mentat的CAD接口读入上面步骤中建好的几何模型,划分网格后完成三维有限元模型的建立。 2.2分析条件假设模型材料和组织假设为连续、均质、各向同性的线弹性材料。由于人体骨骼是一种各向异性的生物体材料,而且各向异性的弹性常数太多,因此一般将其简化为正交各向异性,同时由于骨骼各向异性较弱,故再进一步简化为各向同性。材料受力变形为小变形。 3三维有限元模型的运行分析对于载荷的加载,选择牙位施加,利用软件测算出接触部位面积,换算成面压力来施加。参考国内王景杰等实验测定的各个牙位的加载力值,利用MSC.MARC的面积计算功能,将力转化为加载于面上的压应力,实现对本实验志愿者治疗前、治疗后的前牙咬合、正中咬合和单侧磨牙咬合等六种工况下的加载。 4结果分析测量牙合垫治疗前、牙合治疗后等六种工况下颞下颌关节各个部位的最大和最小Von Mises应力及位移变形情况,观察分析其应力及位移的变化趋势。由于多数学者认为在正常情况下,两侧颞下颌关节及其Von Mises应力分布基本对称,因此本研究只观察单侧颞下颌关节的Von Mises应力变化情况。结果 1通过双源CT扫描仪联合应用Mimics软件、Magics软件和有限元分析软件MSC.Marc无创伤建立活体组织结构的三维有限元模型。本实验我们成功建立了深覆牙合的颞下颌关节紊乱病患者牙合治疗前和牙合垫治疗后的颞下颌关节以及下颌骨的三维有限元模型。 2本实验通过对深覆牙合颞下颌关节紊乱病患者牙合治疗前和牙合治疗后的前牙咬合、正中咬合和单侧磨牙咬合等六种工况进行加载,获得了颞下颌关节各个部位的Von Mises应力和位移变形云图等有限元应力分析资料。 3应力变化规律分析从各种加载工况分析可以看出,在应力变化规律方面,不同加载工况下,各部位应力分布趋势大致相同,应力分布云图类似,只是力的大小不同,说明颞下颌关节关节接触面上规律分布的抗力(应力)能够将不同加载点及加载位置的外力抵抗吸收；单侧磨牙咬合工况时模型接触部位应力最大,其次为正中咬合工况,前牙咬合工况时对应的应力最小：各种工况下,髁状突颈部、髁状突顶部、颞骨关节面、关节盘腹面到背面区域的应力逐渐减小；在同样的咬合方式下,牙合垫治疗后的各个模型的应力均小于牙合垫治疗前,牙合垫治疗后的应力较牙合垫治疗前降低15%至40%；对于深覆牙合的颞下颌关节紊乱病患者,佩戴牙合垫治疗后其颞下颌关节及下颌骨的应力分布较治疗前更合理。 4位移变化规律分析从位移变化规律来说,与应力分布规律类似,单侧磨牙咬合工况时有限元模型产生的位移变形最大,其次是在正中咬合工况时,前牙咬合工况下的位移变形最小。通过牙合垫进行治疗后,各种工况的位移变形较治疗前减小。颞下颌关节区域内,髁状突位移变形最大,关节盘次之,而与颅骨相连的颞骨关节面位移变形最小。结论 1.联合应用双源CT扫描仪、Mimics软件、Magics软件和有限元分析软件MSC.Marc是一种能够快速、精确的建立颞下颌关节及下颌骨三维有限元模型的方法,值得推广应用。 2.利用牙合垫治疗深覆牙合的颞下颌关节紊乱病患者是一种行之有效的方法. 3.对于深覆牙合的颞下颌关节紊乱病患者,在同样的咬合方式下,牙合垫治疗后的颞下颌关节及下颌骨的应力及位移变形均小于牙合垫治疗前,牙合垫治疗后颞下颌关节各个部位的应力分布较牙合垫治疗前更加合理。
[Abstract]:Background of the study

Tempo - mandibular joint disorders ( TMD ) is one of the most common diseases in the oral and maxillofacial region . The etiology of temporo - mandibular joint disorder is very complex , and the etiology of occlusal abnormal is very important in the pathogenesis of temporo - mandibular joint disorder .

There are many methods for the treatment of mandibular joint disorders , such as various medication therapies , various physical treatments , various occlusal treatments including various occlusal pads , etc . The principle of treatment for the mandibular joint disorder is the preferred method of treatment , for example by occlusal pad .

Finite Element Method ( FEM ) has been widely used in the field of medicine in recent years . The finite element method ( FEM ) applied in mechanics has been widely used in the medical field .

Purpose of study

The purpose of this study was to establish a three - dimensional finite element model of the temporo - mandibular joint and the mandible of the patients with mandibular joint disorder by establishing a three - dimensional finite element model for the treatment of the mandibular joint and the mandible , respectively .

Materials and Methods

The establishment and treatment of 1 - D CAD ( Computer Aided Design ) model of the mandibular joint and mandible

1.1 Modeling material

A 24 - year - old patient with mandibular joint disorder was selected as a volunteer . After treatment , two - source CT scanning was performed before and after treatment to obtain the image data of the temporo - mandibular joint area .

1.2 Dual - source CT scan

The scan range is from above the skull to the lower edge of the mandible , and the thin layer image is selectively reconstructed according to the requirement . The scanning parameter is 0.6mm in thickness of the scanning layer , the reconstruction interval is 0.3 mm , the window width 1500 , the window position 450 , the ball tube voltage is 120kv . After the scanning is completed , the acquired scan image data is stored in DICOM format .

1.3 Image Processing

importing the file into the software Mimics , extracting the required target area boundary by using the segmentation tool , and completing the establishment of the geometric model .

1.4 Extraction of the CAD Model of Tempo - mandibular Joint

From the articular surface of the condyle of the mandible , the original shape of the articular disc with the thickness of 2.0 mm was selected from the articular surface of the condyle of the mandible with the aid of Magic12 . 0 software . The original shape of the articular disc and the mandible model were subjected to Boolean operation to obtain the CAD model of the joint disc .

Establishment and treatment of the three - dimensional finite element model of the mandibular joint and mandible

2.1 Generation of 3 - D Finite Element Model

In this paper , the CAD interface of Mentat in Marc2005 is used to read the geometric model built up in the above step , and the establishment of the three - dimensional finite element model is completed .

2.2 Analysis condition assumptions

Model materials and tissues are assumed to be continuous , homogeneous , isotropic linear elastic materials . Because the human skeleton is an anisotropic biological material , and the anisotropic elastic constants are too many , it is generally simplified to the orthogonal anisotropy , while the anisotropy of the bone is weak , so it is further simplified to isotropic .

Operation Analysis of 3 - D Finite Element Model

For the loading of the load , select the tooth position application , calculate the area of the contact area by using the software , and convert the surface pressure to apply .

According to the loading force value of each tooth position measured by Wang Jingjie and other experiments in China , the force is converted into the compressive stress loaded on the surface by using the area calculation function of the MSC . MARC , so as to realize the loading under the six working conditions such as the bite of the anterior teeth , the normal occlusion and the unilateral grinding bite before and after the treatment of the experimental volunteer .

4 Result Analysis

The stress and displacement of the temporo - mandibular joint under six working conditions were measured before and after occlusal therapy , and the variation tendency of stress and displacement was observed .

Results

1 . The three - dimensional finite element model was established by using Mimics software , Magics software and finite element analysis software MSC.Marc for establishing a three - dimensional finite element model of living tissue structure without trauma .

2 This experiment was carried out in six working conditions , such as the bite of the anterior teeth before and after the occlusal treatment of the patients with deep - covered occlusal temporomandibular joint disorder and the occlusion of unilateral maxillary teeth .

Analysis of the Changing Rules of Stress

It can be seen from the analysis of various loading conditions that under different loading conditions , the stress distribution tendency of each part is about the same , the stress distribution cloud image is similar , but the force is different in size , so that the resistance ( stress ) of the regular distribution on the joint surface of the joint joint of the mandibular joint can absorb the external forces at different loading points and loading positions ;
The stress of the contact part of the model was the biggest when unilateral molar occlusion , followed by the normal occlusion condition , the corresponding stress was the minimum in the occlusal condition of the anterior teeth : under various working conditions , the stress of the condylar neck , the condylar eminence , the articular surface of the temporal bone , the ventral surface of the articular disc to the back area gradually decreased ;
In the same occlusal mode , the stress of each model after occlusal pad treatment was less than that before occlusal pad treatment , and the stress after occlusal pad treatment decreased by 15 % to 40 % before treatment .
The stress distribution of the mandibular joint and the mandible was more reasonable before the treatment with occlusal splint .

Analysis of Variation Regularity of 4 Displacement

According to the rule of displacement , the displacement deformation of the finite element model is the most similar to the stress distribution rule , and the displacement deformation is the least under the condition of normal occlusion . The displacement deformation of various working conditions is reduced before the treatment . The displacement deformation of various working conditions is reduced before treatment . The displacement deformation of the condyle is the largest in the region of the temporo - mandibular joint , and the displacement of the articular surface of the temporal bone is minimal .

Conclusion

1 . The joint application of dual - source CT scanner , Mimics software , Magics software and finite element analysis software MSC . Marc is a method which can quickly and accurately establish a three - dimensional finite element model of temporo - mandibular joint and mandible , which is worthy of popularization and application .

2 . It is an effective way to use occlusal splint for the treatment of patients with deep - covered mandibular joint disorder .

3 . The stress and displacement of the temporo - mandibular joint and the mandible after occlusal pad treatment were less than those before and after the treatment of the occlusal pad .

【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：R783.5

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