冲击载荷对种植体周围牙槽骨组织损伤和破坏机理的数值模拟分析

发布时间：2018-06-14 14:03

本文选题：冲击载荷 + 种植体　；参考：《第四军医大学》2016年硕士论文

【摘要】：种植义齿是在口腔缺牙区的牙槽骨内植入种植体,待种植体与骨组织发生骨结合后再在其上端制作完成的一类缺牙修复体。种植义齿能有效地提高咀嚼效率,具有类似真牙的舒适感,而且不损伤邻牙,已逐渐成为牙列缺损和牙列缺失的主要修复形式之一。种植体植入后以骨结合的方式获得牙槽骨组织的固位和支持,骨结合是种植义齿成功的关键,骨结合界面的损坏会导致种植体的松动甚至脱落。在日常咀嚼过程中,种植义齿所承受的咬合力近似于准静态施加于种植体并传导至周围牙槽骨组织上。咀嚼活动中的这种咬合力刺激是维持种植体周围牙槽骨组织稳定和改建的重要因素。但在交通事故、体育竞赛、士兵训练、地质灾害、军事冲突等许多突发情况下,种植义齿往往会承受外部瞬态冲击力的作用。冲击力的特点是作用时间短,持续时间在几十微秒到几毫秒之间,并且载荷幅值远高于准静态载荷。冲击载荷对人体组织所造成的破坏与冲击力的作用时间及幅值密切相关。当冲击载荷的脉冲宽度在微秒量级时,载荷是以应力波的形式在种植体与牙槽骨组织中进行传播,应力波往往会沿着种植体、骨结合界面以及骨组织组成的复合结构中传播和反射,当牙槽骨组织不能发生相应的组织形态改变来吸收和缓冲所承载的冲量时,种植体与骨结合界面便会出现破坏和分离,周围骨组织的微结构也会发生改变。以往关于种植体的生物力学研究多以静态载荷加载下进行分析,对种植体动态加载的研究较少,特别是对冲击载荷作用下种植体周围骨组织的损伤和破坏的研究还未见报道。本研究拟以动物实验模型为基础建立包含骨小梁微观结构的有限元模型,导入冲击载荷的载荷-时间历程,进行动态加载的数值模拟分析。通过改变载荷方向和载荷冲量研究不同冲击载荷作用下种植体周围骨组织的受力情况和应力分布的动态变化。将模拟分析结果与动物实验micro-ct和组织切片vg染色观察到的种植体周围骨结构改变进行比较,研究冲击载荷对种植体周围牙槽骨组织损伤特征和破坏机理,为临床冲击载荷作用下种植体周围骨组织损伤情况的预测及防护提供参考依据。本研究包括以下四部分:1.冲击损伤有限元模型的建立常规动物实验将种植体植入兔股骨,待形成良好的骨结合后对种植体施加冲击载荷,建立冲击损伤实验动物模型,观察种植体周围骨组织形态改变。对实验动物进行micro-ct扫描,将扫描后骨组织数据导入逆向工程软件和有限元分析软件,建立包含种植体与骨小梁结构的适用于冲击载荷加载的有限元模型。实验结果表明:冲击载荷加载后种植体底端骨小梁出现微结构改变,骨结合界面处骨组织出现高应力区,易造成骨结合界面发生脱离和断裂。所建立的微观结构有限元模型能较好的反应出应力波的传播过程和种植体周围骨小梁的应力分布情况,为后续分析冲击损伤特征奠定基础。2.冲击载荷作用下种植体周围骨组织的损伤特征将模拟分析结果与动物实验进行对比,验证数值模拟计算可靠性,获得能准确描述种植体与周围骨组织动力学特性的有限元模型。对上述所建模型施加不同方向和不同作用时间的冲击载荷进行分析,研究不同冲击载荷作用下种植体周围骨组织和骨结合界面处应力波的传播、反射以及组织的受力、变形情况。分析揭示冲击损伤特征,为后续分析冲击后骨组织破坏机理奠定基础。实验结果表明:种植体受到冲击载荷作用时,种植体颈部皮质骨首先出现应力变化,然后应力波从颈部向颊舌侧的松质骨内传播,骨组织发生损伤的部位和程度与载荷方向和载荷冲量相关。随着水平向载荷增大,种植体颊、舌侧及底端松质骨应力分布范围扩大。当载荷作用时间增加时,骨组织最大应力值也增大,同时应力波传播时间随之延长。模拟分析结果与动物实验中出现骨组织损伤的区域相一致。3.冲击载荷作用下种植体周围骨组织的破坏机理将实验测定的兔股骨应力-应变曲线及屈服强度等参数导入有限元模型中,分析种植体周围骨组织和骨结合界面破坏情况,结合骨组织力学特性数据,揭示冲击载荷的破坏机理。实验结果表明:冲击载荷作用下,骨组织高应力区主要分布在种植体底部松质骨内,应力波的透射和反射使得骨结合界面处骨组织中也出现应力集中,这些局部的高应力区会出现骨小梁断裂和骨结合界面的破坏,模拟分析结果与动物实验中出现骨组织损伤的部位相一致。4.下颌后牙种植体有限元模型的建立与种植体周围牙槽骨冲击损伤的预测通过建立人下颌骨种植义齿有限元模型,研究冲击力作用下种植体周围牙槽骨组织的应力分布动态变化,分析牙槽骨组织冲击损伤的发生和特点。实验结果表明:冲击载荷作用下种植体颈部舌侧皮质骨和底端松质骨处出现应力集中。随着载荷冲量增大和方向改变,种植体底部松质骨处应力分布范围增大,应力值升高。冲击载荷形成的应力集中容易造成种植体底部松质骨区域出现骨损伤,提示对冲击损伤患者的临床诊疗过程中,应对其损伤情况做全面检查和评估。结论:1.冲击载荷加载后种植体周围骨组织应力分布主要集中在种植体颈部和底部骨组织,导致周围骨小梁出现断裂。骨小梁应力分布和损伤部位以及损伤程度与冲击载荷方向和载荷冲量相关。2.冲击载荷作用下应力波的传递和反射使得种植体骨结合界面处骨组织中出现高应力区,结合实验测定的骨组织力学参数分析,这些局部的高应力区会出现骨结合界面的破坏。3.本研究所建的微观结构模型通过与动物实验结果对比验证,可较好的反应冲击载荷作用下种植体周围牙槽骨的应力分布和损伤特点,其结果为临床冲击载荷作用下种植体周围骨组织损伤情况的预测及防护提供参考依据。
[Abstract]:Implant denture is implanted in the alveolar bone in the oral cavity, and the implant is combined with bone tissue to make a kind of dental prosthesis. The implant can effectively improve the masticatory efficiency, have the comfort of the true teeth, and do not damage the adjacent teeth, and have gradually become the dentition defect and the dentition missing. One of the main forms of repair. Implant placement and support of the alveolar bone tissue after implantation, bone binding is the key to the success of implant denture. The damage of the bone interface will lead to the loosening and even off of the implant. In the daily chewing process, the bite force of the implant is almost static applied to the implant. It is an important factor in maintaining the stability and reconstruction of the bone tissue around the implant, but in many unexpected situations such as traffic accidents, sports competitions, soldiers' training, geological disasters, military conflicts, and so on, the implant denture often bears the external transient impact force. The impact force is characterized by short action time, a duration of tens of microseconds to several milliseconds, and the load amplitude is far higher than the quasi-static load. The damage caused by the impact load on human tissue is closely related to the time and amplitude of the impact force. When the Mai Chongkuan degree of the impact load is at the magnitude of microseconds, the load is based on the stress wave. The form is propagated in the implant and the alveolar bone tissue, and the stress waves are often propagated and reflected along the compound structure of the implant, bone binding interface and bone tissue. When the alveolar bone can not change the tissue form to absorb and buffer the bearing impulse, the interface of the implant and bone will be damaged. The microstructures of the surrounding bone tissue will also change. The previous biomechanical studies of the implant are mostly analyzed under static loading, and few studies have been made on the dynamic loading of the implants, especially the damage and destruction of the bone tissue around the implant under the impact of the impact load. The experimental model is based on the establishment of a finite element model containing the microstructure of the bone trabecula, which introduces the load time history of the impact load, and carries out the numerical simulation analysis of dynamic loading. By changing the load direction and load impulse, the dynamic changes of the stress and the stress distribution around the implant under different impact loads are studied. The results of simulation were compared with the changes of bone structure around implants observed in animal experiment micro-CT and tissue section VG staining. The damage characteristics and damage mechanism of the impact load on the alveolar bone tissue around the implant were studied, which provided a reference for the prediction and protection of bone tissue damage around the implant body under the effect of the clinical impact load. The study includes the following four parts: 1. the finite element model of impact damage is set up in a conventional animal experiment. The implant is implanted into the rabbit's femur. After a good bone combination is formed, the impact load is applied to the implant, the experimental animal model of the impact damage is established and the morphological changes of the bone around the implant are observed. The micro-CT scan of the experimental animals will be carried out. After scanning, the bone tissue data were introduced into the reverse engineering software and the finite element analysis software to establish a finite element model containing the implant and bone trabecular structure for the loading of the impact load. The experimental results showed that the bone trabecula at the bottom of the implant was changed after the load was loaded, and the bone tissue appeared high stress area at the bone interface, and it was easy to build. The finite element model of microstructure can better reflect the propagation of stress wave and the stress distribution of the bone trabecula around the implant. The damage characteristics of the bone tissue around the implant under.2. impact load will be established by the finite element model. The results were compared with animal experiments to verify the reliability of numerical simulation, and to obtain a finite element model that can accurately describe the dynamic characteristics of the implant and surrounding bone tissue. The impact load of different directions and different action time was applied to the above model, and the bone tissue and bone around the implant under different impact loads were studied. Combined with the propagation of stress waves at the interface, the reflection and the stress and deformation of the tissue, the analysis reveals the characteristics of the impact damage, which lays the foundation for the subsequent analysis of the destruction mechanism of the bone tissue after the impact analysis. The experimental results show that the stress changes in the cortical bone of the implant neck and the stress wave from the neck to the cheek when the implant is affected by the impact load. The location and degree of the injury in the cancellous bone of the tongue is related to the load direction and load impulse. With the increase of the horizontal load, the stress distribution of the cancellous bone of the implant cheek, the tongue side and the bottom is enlarged. The maximum stress value of the bone tissue increases as the loading time increases, and the propagation time of the stress wave is prolonged. The damage mechanism of the bone tissue around the implant under the same.3. impact load on the area of the bone tissue damage in the animal experiment was introduced into the finite element model of the measured stress strain curve and yield strength of the rabbit femur, and the damage of the periimplant bone tissue and the bone bonding interface was analyzed. The mechanical properties of the bone tissue reveal the failure mechanism of the impact load. The experimental results show that the high stress area of bone tissue is mainly distributed in the cancellous bone at the bottom of the implant under the impact load, and the stress wave is transmitted and reflected in the bone tissue at the interface of the bone, and the bone is small in these local high stress areas. The failure of the interface between the fracture of the beam and the bone, the simulation analysis is consistent with the site of the bone tissue damage in the animal experiment. The establishment of the finite element model of the.4. mandibular posterior implant and the prediction of the impact damage of the alveolar bone around the implant are predicted by establishing the finite element model of the implant denture of the human mandible, and the study of the surrounding implant under the impact force. The dynamic changes in the stress distribution of the alveolar bone tissue and the occurrence and characteristics of the impact damage of the alveolar bone tissue were analyzed. The experimental results showed that the stress concentration occurred at the lingual cortical bone and the cancellous bone in the bottom of the implant neck. The stress distribution of the cancellous bone at the bottom of the implant was increased with the load impulse increase and the direction change. The stress concentration increased. The stress concentration formed by the impact load may cause bone damage in the region of the cancellous bone at the bottom of the implant, which suggests that the damage of the patients with impact injury should be examined and evaluated comprehensively in the process of clinical diagnosis and treatment. Conclusion: the stress distribution of the perimenal bone tissue in the implant body is mainly concentrated in the implant neck after the loading of the 1. impact load. Bone trabecular fracture in the part and bottom of the bone leads to fracture of the surrounding trabeculae. The stress distribution and damage position of the trabecular bone, the degree of damage, the direction of the impact load and the load impulse are related to the transmission and reflection of the stress wave under the impact of the.2. impact load, which makes the bone tissue in the implant bone binding interface present high stress zone, combined with the experimental bone tissue. The mechanical parameters analysis, these local high stress areas will destroy the bone bonding interface. The microstructure model built by the.3. study is verified by comparison with the animal experimental results. The stress distribution and damage characteristics of the alveolar bone around the implant under the impact of the impact load are better. The results are under the effect of the clinical impact load. Provide a basis for prediction and protection of bone tissue injury around the body.
【学位授予单位】：第四军医大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：R783.6

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