本文選題：牙合墊　切入點：深覆牙合　出處：《山東大學》2014年博士論文

【摘要】：研究背景 顳下頜關(guān)節(jié)紊亂病(temporomandibular joint disorders, TMD)是口腔頜面部常見的疾病之一。顳下頜關(guān)節(jié)紊亂病的病因非常復(fù)雜,咬合異常病因?qū)W說在顳下頜關(guān)節(jié)紊亂病中占有非常重要的地位。許多異常的咬合因素,比如深覆牙合、第三磨牙過長、部分后牙的反牙合、牙合干擾等等都曾經(jīng)被報道過與顳下頜關(guān)節(jié)紊亂病的病因有關(guān)。其中深覆牙合能夠影響咀嚼運動和肌電活動,與顳下頜關(guān)節(jié)紊亂病的發(fā)生密切相關(guān),有研究顯示深覆牙合的患者出現(xiàn)顳下頜關(guān)節(jié)紊亂病的幾率是正常人的13.2倍。 顳下頜關(guān)節(jié)紊亂病的治療方法很多,如各種藥物治療,各種物理治療,各種牙合治療包括各種牙合墊等。顳下頜關(guān)節(jié)紊亂病的治療原則是首選可逆性的治療方法,比如說通過牙合墊來做牙合間矯治。 隨著近些年來各個學科之間交流的日益廣泛,在力學研究中應(yīng)用的有限元分析方法(Finite Element Method, FEM)已經(jīng)被廣泛應(yīng)用到了醫(yī)學領(lǐng)域。Friedenberg在1969年第一次將有限元分析方法應(yīng)用于醫(yī)學領(lǐng)域。Thresher和Farah于1973年將二維有限元分析方法引入到了口腔醫(yī)學領(lǐng)域。目前有限元分析方法應(yīng)用的范圍已經(jīng)涉及到口腔醫(yī)學的各個領(lǐng)域。三維有限元法已被廣泛應(yīng)用到單個牙齒、牙周膜、牙槽骨、樁核冠、可摘局部義齒、固定義齒、種植義齒、全口義齒及顳下頜關(guān)節(jié)的應(yīng)力分析。但是,對于深覆牙合的顳下頜關(guān)節(jié)紊亂病患者,運用三維有限元分析方法對其進行牙合治療前后的的顳下頜關(guān)節(jié)進行受力分析,還未見相關(guān)報道。 研究目的 本研究就是通過建立深覆牙合顳下頜關(guān)節(jié)紊亂病患者的顳下頜關(guān)節(jié)以及下頜骨的三維有限元模型,分別在牙合墊治療前牙合墊治療后進行加載并分析顳下頜關(guān)節(jié)以及下頜骨的應(yīng)力分布情況,以便更好地深入研究顳下頜關(guān)節(jié)紊亂病患者的髁狀突、關(guān)節(jié)窩和關(guān)節(jié)盤以及與下頜骨之間的生物力學關(guān)系,為臨床設(shè)計提供生物力學參考依據(jù)。 材料與方法 1顳下頜關(guān)節(jié)以及下頜骨的三維CAD (Computer Aided Design,計算機輔助設(shè)計)模型的建立和處理 1.1建模素材 選擇一名24歲的深覆牙合顳下頜關(guān)節(jié)紊亂病患者作為志愿者,通過戴用牙合來治療顳下頜關(guān)節(jié)紊亂病。治療前后分別行雙源CT掃描,獲得顳下頜關(guān)節(jié)區(qū)的影像資料。 1.2雙源CT掃描 掃描的范圍自顱骨上方至下頜骨下緣,根據(jù)需要選擇性重建薄層圖像,掃描參數(shù)為掃描層厚0.6mm,重建間隔0.3mm,窗寬1500,窗位450,球管電壓為120kv。掃描完成后將獲得的掃描影像數(shù)據(jù)以DICOM格式存儲。 1.3圖像處理 將上述文件導入軟件Mimics當中,利用其中的分割工具將需要的目標區(qū)域邊界提取出來,完成幾何模型的建立。 1.4顳下頜關(guān)節(jié)盤CAD模型的提取 借助Magics12.0軟件,從下頜骨髁狀突的關(guān)節(jié)面選取與關(guān)節(jié)盤匹配的位置區(qū)域生成厚度約為2.0mm厚的關(guān)節(jié)盤原始形狀,將原始形狀的關(guān)節(jié)盤與下頜骨模型進行布爾運算,即可得到顳下頜關(guān)節(jié)盤的CAD模型。 2顳下頜關(guān)節(jié)以及下頜骨的三維有限元模型的建立和處理 2.1三維有限元模型的生成 采用軟件MSC.Marc2005中Mentat的CAD接口讀入上面步驟中建好的幾何模型,劃分網(wǎng)格后完成三維有限元模型的建立。 2.2分析條件假設(shè) 模型材料和組織假設(shè)為連續(xù)、均質(zhì)、各向同性的線彈性材料。由于人體骨骼是一種各向異性的生物體材料,而且各向異性的彈性常數(shù)太多,因此一般將其簡化為正交各向異性,同時由于骨骼各向異性較弱,故再進一步簡化為各向同性。材料受力變形為小變形。 3三維有限元模型的運行分析 對于載荷的加載,選擇牙位施加,利用軟件測算出接觸部位面積,換算成面壓力來施加。 參考國內(nèi)王景杰等實驗測定的各個牙位的加載力值,利用MSC.MARC的面積計算功能,將力轉(zhuǎn)化為加載于面上的壓應(yīng)力,實現(xiàn)對本實驗志愿者治療前、治療后的前牙咬合、正中咬合和單側(cè)磨牙咬合等六種工況下的加載。 4結(jié)果分析 測量牙合墊治療前、牙合治療后等六種工況下顳下頜關(guān)節(jié)各個部位的最大和最小Von Mises應(yīng)力及位移變形情況,觀察分析其應(yīng)力及位移的變化趨勢。由于多數(shù)學者認為在正常情況下,兩側(cè)顳下頜關(guān)節(jié)及其Von Mises應(yīng)力分布基本對稱,因此本研究只觀察單側(cè)顳下頜關(guān)節(jié)的Von Mises應(yīng)力變化情況。 結(jié)果 1通過雙源CT掃描儀聯(lián)合應(yīng)用Mimics軟件、Magics軟件和有限元分析軟件MSC.Marc無創(chuàng)傷建立活體組織結(jié)構(gòu)的三維有限元模型。本實驗我們成功建立了深覆牙合的顳下頜關(guān)節(jié)紊亂病患者牙合治療前和牙合墊治療后的顳下頜關(guān)節(jié)以及下頜骨的三維有限元模型。 2本實驗通過對深覆牙合顳下頜關(guān)節(jié)紊亂病患者牙合治療前和牙合治療后的前牙咬合、正中咬合和單側(cè)磨牙咬合等六種工況進行加載,獲得了顳下頜關(guān)節(jié)各個部位的Von Mises應(yīng)力和位移變形云圖等有限元應(yīng)力分析資料。 3應(yīng)力變化規(guī)律分析 從各種加載工況分析可以看出,在應(yīng)力變化規(guī)律方面,不同加載工況下,各部位應(yīng)力分布趨勢大致相同,應(yīng)力分布云圖類似,只是力的大小不同,說明顳下頜關(guān)節(jié)關(guān)節(jié)接觸面上規(guī)律分布的抗力(應(yīng)力)能夠?qū)⒉煌虞d點及加載位置的外力抵抗吸收；單側(cè)磨牙咬合工況時模型接觸部位應(yīng)力最大,其次為正中咬合工況,前牙咬合工況時對應(yīng)的應(yīng)力最�。焊鞣N工況下,髁狀突頸部、髁狀突頂部、顳骨關(guān)節(jié)面、關(guān)節(jié)盤腹面到背面區(qū)域的應(yīng)力逐漸減��；在同樣的咬合方式下,牙合墊治療后的各個模型的應(yīng)力均小于牙合墊治療前,牙合墊治療后的應(yīng)力較牙合墊治療前降低15%至40%；對于深覆牙合的顳下頜關(guān)節(jié)紊亂病患者,佩戴牙合墊治療后其顳下頜關(guān)節(jié)及下頜骨的應(yīng)力分布較治療前更合理。 4位移變化規(guī)律分析 從位移變化規(guī)律來說,與應(yīng)力分布規(guī)律類似,單側(cè)磨牙咬合工況時有限元模型產(chǎn)生的位移變形最大,其次是在正中咬合工況時,前牙咬合工況下的位移變形最小。通過牙合墊進行治療后,各種工況的位移變形較治療前減小。顳下頜關(guān)節(jié)區(qū)域內(nèi),髁狀突位移變形最大,關(guān)節(jié)盤次之,而與顱骨相連的顳骨關(guān)節(jié)面位移變形最小。 結(jié)論 1.聯(lián)合應(yīng)用雙源CT掃描儀、Mimics軟件、Magics軟件和有限元分析軟件MSC.Marc是一種能夠快速、精確的建立顳下頜關(guān)節(jié)及下頜骨三維有限元模型的方法,值得推廣應(yīng)用。 2.利用牙合墊治療深覆牙合的顳下頜關(guān)節(jié)紊亂病患者是一種行之有效的方法. 3.對于深覆牙合的顳下頜關(guān)節(jié)紊亂病患者,在同樣的咬合方式下,牙合墊治療后的顳下頜關(guān)節(jié)及下頜骨的應(yīng)力及位移變形均小于牙合墊治療前,牙合墊治療后顳下頜關(guān)節(jié)各個部位的應(yīng)力分布較牙合墊治療前更加合理。
[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 .

【學位授予單位】：山東大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：R783.5

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