牙根纵裂发生机理的力学研究

Vertical root fracture (VRF)is an important reason for tooth loss. Sofar there is no effective treatment for it .This catastrophic result was caused by the repeated loading of masticating force transmitted from crown down to the root.The process of development of dentin cracks under occlusal stress is crucial for understanding the mechanism of vertical root fracture and improving the prognosis of it. Our previous study found that ageing significantly affect the distribution of human enamel fracture mechanics, while studies on the incidence of vertical root fracture demonstrated that aging, pathological changes of dentin and wear of crowns are risk factors for the disease.Accordingly, we plan to (1) measure the root dentin fracture mechanics properties in both micro-and macro view and investigate how the aging, pathological changes of dnetin ; (2) establish numerical and physical research models of root vertical fracture to clarify the stress distribution and crack damage evolution in root under and the mechanism of the development of vertical root fracture.The project can lay the foundation for the new method of vertical root fracture studies,advance the diagnosis and treatment of disease, reduce health care costs of patients and has important significance and broad prospect.

牙根纵裂是引起人失牙的重要原因，尚无有效治疗手段。该疾病是牙齿行使咀嚼功能过程中外力经牙冠传导至牙根，引起牙根灾变的结果。这一过程如何影响牙本质裂纹发生发展，是解释牙根纵裂发生机理，提高该病预后亟需填补的研究空白。申请者所在课题组前期研究发现人牙釉质的增龄性变化明显影响牙釉质断裂力学性能，同时，对牙根纵裂好发病因的研究显示牙本质的增龄性，病理性改变和牙冠磨耗为该病易感因素。据此，本课题拟通过（1）测量根部牙本质微观及宏观断裂力学性能，考察牙本质的增龄性、病理性变化通过何种途径对其性能造成影响；（2）在此基础上建立牙根纵裂的数值和实体研究模型，阐明咬合力作用下牙根的应力分布特点的和裂纹损伤演化规律，明确各易感因素在裂纹发生发展中的作用，揭示牙根纵裂的发生机理。该项目将为牙根纵裂相关研究奠定基础，并对该疾病预防和诊治新方法的推进，降低患者医疗成本具有重要的理论意义和广阔的应用前景。

牙根纵裂后果严重，尚无有效治疗手段，是引起人失牙的重要原因。裂纹起源于牙根部牙本质，与牙根受力状态及牙根部牙本质力学性能密切相关。本课题围绕牙本质的增龄性、病理性变化及口腔治疗等因素对牙根部牙本质受力及裂纹发生发展的影响，探索牙齿在咬合力作用下的应力分布特点和裂纹损伤演化规律，揭示牙根纵裂的发生机理。.研究结果表明根部牙本质的显微结构、化学成分和力学性能自上向下存在空间变异性，且随着年龄发生变化，老年者根尖牙本质较年轻者具有更高的应力水平，由此推测在口腔循环咀嚼受力下可能导致老年根尖牙本质的疲劳寿命下降。牙根的颊舌面较近远中面承受更大的应力。随磨耗的加重，近中根面应力向根下段的转移更明显，导致近中根较远中根更容易发生根折，结果与牙根纵裂的临床特征相符。此情况主要存在于垂直加载过程。此外，根管弯曲、镍钛器械的材质和运动模式等因素均对牙本质微裂形成和发展产生影响。不同器械之间存在差异，在根管治疗中应合理选择预备成形的器械，以达到更好的预后和患牙保存率。本项目成果为牙根纵裂相关研究奠定基础，为推断牙根纵裂易感人群、预测裂纹发展趋势、制定牙根纵裂防治计划及研制牙本质仿生材料提供思路。.