牙釉质折裂发生机理的多尺度研究

Teeth bear many physiological functions such as chewing of food, pronunciation, and maintenance of human facial appearance. Tooth fracture is one of the three major reasons of tooth loss. It was a catastrophic result caused by the external force during mastication. Tooth fracture usually originated in the enamel, and is closely related to the mechanical properties and structural characteristics of the enamel. In the study of the primary cracking of the teeth, the effects of enamel structure at different scales on the crack is the most critical and the fundamental issue need to be resolved..This project will be carried out on human enamel. We will conduct the following studies: 1) Observe the multi-scale structure of enamel of clinically fractured teeth; 2) Establish the multi-scale three-dimensional finite element model of posterior teeth; 3) Conduct ex situ loading tests on extracted human teeth in order to analyze the multi-scale feature of pattern and path of enamel crack and fracture. Through these studies, we may understand the stress distribution characteristics of molars under occlusal stress, as well as the effect of the multi-scale structure, component, mechanical properties and stress distribution of enamel in the initiation and development of the crack, thus gain a better understand of the mechanism of tooth fracture..The results of the project may have great implications in enrichment of the bio-mechanical speculative knowledge of human body and oral cavity, speculation of susceptible populations of cracked tooth, prediction of the trends and prognosis the crack, as well as the development of prevention and treatment programs of cracked tooth.

牙齿承担咀嚼食物、发音和维持颜面外形等功能。牙折裂是牙齿行使咀嚼功能这一力学作用过程中由外力引起牙齿灾变的结果，是引起人失牙的三大原因之一。牙釉质是人最硬组织，但牙折裂多起源于牙釉质，并与釉质的结构特性和力学性能密切相关。研究牙齿原发性开裂的发生机理，牙釉质不同尺度结构对裂纹发生发展的影响是急需解决的最关键基础性问题之一。.本课题以人牙釉质为研究对象，通过观察和测量牙釉质多尺度结构与性能，建立牙齿釉质开裂损伤演化的力学理论模型，结合球压实验观察及有限元计算结果，分析牙釉质不同尺度水平上的结构、组成、力学性能对其裂纹发生发展的影响，明确后牙在咬合力作用下的应力分布特点和裂纹损伤演化规律,探讨牙釉质折裂的发生机理。.本项目成果将对丰富人体和口腔生物力学理论知识、推断牙折裂易感人群、预测裂纹发展趋势和预后、制定牙折裂防治计划及研制仿生材料都具十分重要意义。

牙齿承担咀嚼食物、发音和维持颜面外形等功能。牙折裂是牙齿行使咀嚼功能这一力学作用过程中由外力引起牙齿灾变的结果，是引起人失牙的三大原因之一。牙釉质是人体最硬组织，但牙折裂多起源于牙釉质，并与釉质的结构特性和力学性能密切相关。研究牙齿原发性开裂的发生机理，牙釉质不同尺度结构对裂纹发生发展的影响是急需解决的最关键基础性问题之一。.本研究借助力学和生物材料学的研究思想和研究手段，通过对离体牙的准静态及疲劳加载，对牙釉质牙本质复合体原位单轴压缩断裂行为的研究，以及对釉质微结构力学性能和化学成分的增龄性改变的相关测量，探讨牙齿损伤断裂及其影响因素，跨尺度研究牙齿损伤断裂发生的力学机制，同时，在研究中将牙齿的另一重要组织-牙本质共同纳入研究比较，并考察医源性因素等对牙齿折裂的影响，从全局观考察牙齿折裂发生机理。.本研究成果表明牙齿发生整体失效需在突发极高载荷以及更靠近牙齿中轴的条件下发生。硬物的尺寸也是导致整体失效的关键因素。不同部位牙齿断裂特点的差异与其加载方式和宏观结构关系更密切。同时，牙齿硬组织微结构存在对抗裂纹的自我保护机制：釉质的绞釉部分存在增韧机制（架桥韧带、裂纹桥接等），从釉质到釉牙本质界（DEJ）处韧性的明显改变使得绝大多数情况下裂纹在DEJ处停止或仅穿入少量牙本质，从而保护内部牙本质结构，避免发生结构性破坏。人牙釉质及牙本质的力学性能呈现空间分布变化，并与年龄变化密切相关。医源性因素可能导致折裂隐患，牙根弯曲程度、牙本质形态、器械锥度和横截面设计等因素均可能促成牙本质裂纹的形成。.本项目成果将对丰富人体和口腔生物力学理论知识、推断牙折裂易感人群、预测裂纹发展趋势和预后、制定牙折裂防治计划及研制仿生材料都具十分重要意义。