本文選題：沖擊載荷 + 種植體��； 參考：《第四軍醫(yī)大學》2016年碩士論文

【摘要】：種植義齒是在口腔缺牙區(qū)的牙槽骨內植入種植體,待種植體與骨組織發(fā)生骨結合后再在其上端制作完成的一類缺牙修復體。種植義齒能有效地提高咀嚼效率,具有類似真牙的舒適感,而且不損傷鄰牙,已逐漸成為牙列缺損和牙列缺失的主要修復形式之一。種植體植入后以骨結合的方式獲得牙槽骨組織的固位和支持,骨結合是種植義齒成功的關鍵,骨結合界面的損壞會導致種植體的松動甚至脫落。在日常咀嚼過程中,種植義齒所承受的咬合力近似于準靜態(tài)施加于種植體并傳導至周圍牙槽骨組織上。咀嚼活動中的這種咬合力刺激是維持種植體周圍牙槽骨組織穩(wěn)定和改建的重要因素。但在交通事故、體育競賽、士兵訓練、地質災害、軍事沖突等許多突發(fā)情況下,種植義齒往往會承受外部瞬態(tài)沖擊力的作用。沖擊力的特點是作用時間短,持續(xù)時間在幾十微秒到幾毫秒之間,并且載荷幅值遠高于準靜態(tài)載荷。沖擊載荷對人體組織所造成的破壞與沖擊力的作用時間及幅值密切相關。當沖擊載荷的脈沖寬度在微秒量級時,載荷是以應力波的形式在種植體與牙槽骨組織中進行傳播,應力波往往會沿著種植體、骨結合界面以及骨組織組成的復合結構中傳播和反射,當牙槽骨組織不能發(fā)生相應的組織形態(tài)改變來吸收和緩沖所承載的沖量時,種植體與骨結合界面便會出現(xiàn)破壞和分離,周圍骨組織的微結構也會發(fā)生改變。以往關于種植體的生物力學研究多以靜態(tài)載荷加載下進行分析,對種植體動態(tài)加載的研究較少,特別是對沖擊載荷作用下種植體周圍骨組織的損傷和破壞的研究還未見報道。本研究擬以動物實驗模型為基礎建立包含骨小梁微觀結構的有限元模型,導入沖擊載荷的載荷-時間歷程,進行動態(tài)加載的數(shù)值模擬分析。通過改變載荷方向和載荷沖量研究不同沖擊載荷作用下種植體周圍骨組織的受力情況和應力分布的動態(tài)變化。將模擬分析結果與動物實驗micro-ct和組織切片vg染色觀察到的種植體周圍骨結構改變進行比較,研究沖擊載荷對種植體周圍牙槽骨組織損傷特征和破壞機理,為臨床沖擊載荷作用下種植體周圍骨組織損傷情況的預測及防護提供參考依據(jù)。本研究包括以下四部分:1.沖擊損傷有限元模型的建立常規(guī)動物實驗將種植體植入兔股骨,待形成良好的骨結合后對種植體施加沖擊載荷,建立沖擊損傷實驗動物模型,觀察種植體周圍骨組織形態(tài)改變。對實驗動物進行micro-ct掃描,將掃描后骨組織數(shù)據(jù)導入逆向工程軟件和有限元分析軟件,建立包含種植體與骨小梁結構的適用于沖擊載荷加載的有限元模型。實驗結果表明:沖擊載荷加載后種植體底端骨小梁出現(xiàn)微結構改變,骨結合界面處骨組織出現(xiàn)高應力區(qū),易造成骨結合界面發(fā)生脫離和斷裂。所建立的微觀結構有限元模型能較好的反應出應力波的傳播過程和種植體周圍骨小梁的應力分布情況,為后續(xù)分析沖擊損傷特征奠定基礎。2.沖擊載荷作用下種植體周圍骨組織的損傷特征將模擬分析結果與動物實驗進行對比,驗證數(shù)值模擬計算可靠性,獲得能準確描述種植體與周圍骨組織動力學特性的有限元模型。對上述所建模型施加不同方向和不同作用時間的沖擊載荷進行分析,研究不同沖擊載荷作用下種植體周圍骨組織和骨結合界面處應力波的傳播、反射以及組織的受力、變形情況。分析揭示沖擊損傷特征,為后續(xù)分析沖擊后骨組織破壞機理奠定基礎。實驗結果表明:種植體受到沖擊載荷作用時,種植體頸部皮質骨首先出現(xiàn)應力變化,然后應力波從頸部向頰舌側的松質骨內傳播,骨組織發(fā)生損傷的部位和程度與載荷方向和載荷沖量相關。隨著水平向載荷增大,種植體頰、舌側及底端松質骨應力分布范圍擴大。當載荷作用時間增加時,骨組織最大應力值也增大,同時應力波傳播時間隨之延長。模擬分析結果與動物實驗中出現(xiàn)骨組織損傷的區(qū)域相一致。3.沖擊載荷作用下種植體周圍骨組織的破壞機理將實驗測定的兔股骨應力-應變曲線及屈服強度等參數(shù)導入有限元模型中,分析種植體周圍骨組織和骨結合界面破壞情況,結合骨組織力學特性數(shù)據(jù),揭示沖擊載荷的破壞機理。實驗結果表明:沖擊載荷作用下,骨組織高應力區(qū)主要分布在種植體底部松質骨內,應力波的透射和反射使得骨結合界面處骨組織中也出現(xiàn)應力集中,這些局部的高應力區(qū)會出現(xiàn)骨小梁斷裂和骨結合界面的破壞,模擬分析結果與動物實驗中出現(xiàn)骨組織損傷的部位相一致。4.下頜后牙種植體有限元模型的建立與種植體周圍牙槽骨沖擊損傷的預測通過建立人下頜骨種植義齒有限元模型,研究沖擊力作用下種植體周圍牙槽骨組織的應力分布動態(tài)變化,分析牙槽骨組織沖擊損傷的發(fā)生和特點。實驗結果表明:沖擊載荷作用下種植體頸部舌側皮質骨和底端松質骨處出現(xiàn)應力集中。隨著載荷沖量增大和方向改變,種植體底部松質骨處應力分布范圍增大,應力值升高。沖擊載荷形成的應力集中容易造成種植體底部松質骨區(qū)域出現(xiàn)骨損傷,提示對沖擊損傷患者的臨床診療過程中,應對其損傷情況做全面檢查和評估。結論:1.沖擊載荷加載后種植體周圍骨組織應力分布主要集中在種植體頸部和底部骨組織,導致周圍骨小梁出現(xiàn)斷裂。骨小梁應力分布和損傷部位以及損傷程度與沖擊載荷方向和載荷沖量相關。2.沖擊載荷作用下應力波的傳遞和反射使得種植體骨結合界面處骨組織中出現(xiàn)高應力區(qū),結合實驗測定的骨組織力學參數(shù)分析,這些局部的高應力區(qū)會出現(xiàn)骨結合界面的破壞。3.本研究所建的微觀結構模型通過與動物實驗結果對比驗證,可較好的反應沖擊載荷作用下種植體周圍牙槽骨的應力分布和損傷特點,其結果為臨床沖擊載荷作用下種植體周圍骨組織損傷情況的預測及防護提供參考依據(jù)。
[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.
【學位授予單位】：第四軍醫(yī)大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：R783.6

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