【摘要】：口腔種植體能顯著提高患者的咀嚼功能,且具有類似真牙的舒適感覺,臨床上已經(jīng)被廣泛應(yīng)用于義齒修復(fù)。隨著口腔種植技術(shù)的發(fā)展,其生物力學(xué)性能成為這一領(lǐng)域的研究熱點(diǎn)。有限元法因其具有無創(chuàng)性、計(jì)算高效性、模型可重復(fù)性、可查看任意結(jié)構(gòu)處應(yīng)力值等優(yōu)點(diǎn),成為該領(lǐng)域重要的研究方法。相關(guān)的口腔生物力學(xué)有限元研究表明,影響其分析結(jié)果準(zhǔn)確性的三個(gè)關(guān)鍵因素是模型、材料屬性和邊界條件。由于牙周膜等軟組織的提取仍然存在一定難度,因此常規(guī)的口腔有限元模型往往忽視了軟組織的作用,此外由于下頜運(yùn)動的復(fù)雜性,邊界約束條件也常被簡化處理,而這些因素都會影響計(jì)算結(jié)果的準(zhǔn)確性。本文建立了含種植體的完整口腔有限元模型,研究了牙周膜與不同邊界約束條件對計(jì)算結(jié)果的影響。采用逆向建模軟件從計(jì)算機(jī)斷層掃描圖像中提取出完整下頜骨及牙列三維幾何模型,利用多邊形及曲面處理功能分離出皮質(zhì)骨、松質(zhì)骨和完整下牙列,并使用抽殼功能生成了牙周膜及顳下頜關(guān)節(jié)軟組織,從而獲得了完整的口腔三維幾何模型。此方法獲得的幾何模型更符合真實(shí)的口腔結(jié)構(gòu),有助于建立有效的含種植體口腔生物力學(xué)有限元模型。應(yīng)用顳下頜關(guān)節(jié)運(yùn)動軌跡分析儀,獲取了下頜最大垂直開閉口運(yùn)動時(shí)髁突中心的運(yùn)動數(shù)據(jù)。髁突中心點(diǎn)運(yùn)動軌跡表明下頜開閉口運(yùn)動并不是單一的鉸鏈運(yùn)動,而是髁突中心點(diǎn)轉(zhuǎn)動與滑動的結(jié)合。由數(shù)據(jù)分析獲得的下頜中切點(diǎn)運(yùn)動軌跡表明下頜骨并不是做剛體運(yùn)動,以往采用髁突中心點(diǎn)軌跡推導(dǎo)中切點(diǎn)軌跡的方法并不可行。結(jié)合下頜運(yùn)動分析,選取前人研究文獻(xiàn)中簡化的邊界約束條件與本文依據(jù)下頜實(shí)際運(yùn)動所建立的邊界約束條件,研究其在口腔生物力學(xué)中對牙槽骨乃至整個(gè)下頜骨應(yīng)力計(jì)算結(jié)果的影響。分析結(jié)果表明邊界約束條件對下頜骨應(yīng)力分布形式有顯著影響,且不同邊界約束條件下最大應(yīng)力值出現(xiàn)在不同區(qū)域。在含種植體口腔生物力學(xué)模型中,對牙周膜作用的分析發(fā)現(xiàn),有無牙周膜對種植體、牙槽骨及下頜骨上的應(yīng)力分布形式基本沒有影響,但是有牙周膜作用時(shí),種植體骨結(jié)合面上最大應(yīng)力值減小42.96%,牙槽骨上的最大應(yīng)力值會減小29.03%～52.20%,因此牙周膜能減少從牙齒傳遞到牙槽骨上的應(yīng)力;針對邊界約束條件的分析結(jié)果與不含種植體口腔模型一致,即邊界約束條件不僅會影響各組織結(jié)構(gòu)上的應(yīng)力分布形式,還會影響應(yīng)力值大小。因此在含種植體口腔生物力學(xué)三維有限元建模中應(yīng)考慮牙周膜組織的作用,并設(shè)置更符合下頜實(shí)際運(yùn)動情況的邊界約束條件,以提高有限元模型的精確性和計(jì)算結(jié)果的可靠性。
[Abstract]:Oral implants can improve the masticatory function of the patients significantly and have the comfortable feeling similar to the true teeth, which has been widely used in the clinical application of denture restoration. With the development of dental implant technology, biomechanical properties of dental implant have become a hotspot in this field. Finite element method (FEM) has become an important research method in this field because of its advantages of noninvasive, efficient calculation, repeatability of the model, and the ability to view the stress values of arbitrary structures. The related finite element analysis of oral biomechanics shows that the three key factors affecting the accuracy of the analytical results are the model, material properties and boundary conditions. Because the extraction of periodontal ligament and other soft tissue is still difficult, the traditional oral finite element model often ignores the role of soft tissue, in addition, because of the complexity of mandibular movement, boundary constraints are often simplified. These factors will affect the accuracy of the calculation results. In this paper, a complete oral finite element model with implants is established, and the effects of periodontal ligament and different boundary constraints on the calculation results are studied. Three dimensional geometric models of complete mandible and dentition were extracted from computed tomography images by reverse modeling software. Cortical bone, cancellous bone and complete lower dentition were separated by polygon and curved surface processing. The periodontal ligament and temporomandibular joint soft tissue were generated by the function of exfoliation, and a complete 3D model of oral cavity was obtained. The geometric model obtained by this method is more consistent with the real oral structure and is helpful to establish an effective finite element model of dental biomechanics containing implants. Using the temporomandibular joint motion trajectory analyzer, the movement data of the condyle center during the maximal vertical opening and closing of the mandible were obtained. The movement of the central point of the condyle indicates that the movement of the mandibular opening and closing is not a single hinge motion, but a combination of the rotation of the central point of the condyle and the sliding of the central point of the condyle. The results of data analysis show that the mandible is not rigid body motion, and it is not feasible to use condylar centroid locus to deduce the tangent point trajectory. Combined with the analysis of mandibular movement, the simplified boundary constraint condition in previous literatures and the boundary constraint condition established in this paper according to the actual movement of mandible are selected. To study the effect of the stress of alveolar bone and mandible in oral biomechanics. The results show that the boundary constraint conditions have a significant effect on the distribution of mandibular stress, and the maximum stress values under different boundary constraints appear in different regions. In the dental biomechanical model with implants, it was found that periodontal ligament had no effect on the stress distribution of implant, alveolar bone and mandible, but the periodontal ligament had no effect on the stress distribution of implant, alveolar bone and mandible. The maximum stress on implant bone joint plane decreased 42.96, and the maximum stress value on alveolar bone decreased 29.0352.20, so periodontal ligament can reduce the stress transferred from tooth to alveolar bone. The analytical results of boundary constraint conditions are consistent with the oral model without implants, that is, boundary constraints will not only affect the stress distribution in various tissue structures, but also affect the magnitude of stress values. Therefore, the role of periodontal ligament should be considered in the three-dimensional finite element modeling of dental biomechanics with implants, and the boundary constraint conditions should be set up in order to improve the accuracy of the finite element model and the reliability of the calculation results.
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：R783;R318.01

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