Department of Mechanics, Shanghai University, Shanghai 200444, People's Republic of China; Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai 200072, People's Republic of China.
Department of Mechanics, Shanghai University, Shanghai 200444, People's Republic of China; Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai 200072, People's Republic of China.
J Mech Behav Biomed Mater. 2018 May;81:149-160. doi: 10.1016/j.jmbbm.2018.02.029. Epub 2018 Feb 26.
Dentin is a biocomposite possessing complex hierarchical structure, which endows this hard tissue with excellent damage tolerance. In this study, crack growth in dentin at the microstructural scale is investigated and the synergistic effects of plastic deformation of intertubular dentin (ITD), elasticity and fracture properties of peritubular dentin (PTD), and fracture properties of PTD/ITD interface on the fracture of dentin are explored. A micromechanical model is developed, which captures the experimentally observed fracture process of dentin, i.e. occurrence of microcracking of PTD ahead of the main crack. It is found through numerical simulations that high relative stiffness and low cohesive strength of PTD increase the propensity of microcracking of PTD, whereas reduce the plastic dissipation and toughness of the microstructure of dentin. The microcracking of PTD can be also promoted by low toughness of PTD. The large friction angle and weak strain hardening of ITD could promote the microcracking of PTD, and simultaneously enhance the toughness of the microstructure of dentin. In addition, it is identified that the cohesive strength of the PTD/ITD interface plays a crucial role in dominating fracture mechanisms; low cohesive strength leads to fracture of interface and suppresses microcracking of PTD, which provides an explanation for the crack deflection along interface observed in experiments. Nevertheless, the toughness of interface has a negligible influence on the fracture of dentin.
牙本质是一种具有复杂层次结构的生物复合材料，这使这种硬组织具有出色的耐损伤能力。本研究在微观结构尺度上研究了牙本质中的裂纹扩展，并探讨了管间牙本质（ITD）的塑性变形、管周牙本质（PTD）的弹性和断裂性能以及 PTD/ITD 界面的断裂性能对牙本质断裂的协同作用。建立了一个细观力学模型，该模型捕捉到了牙本质的实验观察到的断裂过程，即主裂纹前 PTD 的微裂纹发生。通过数值模拟发现，PTD 的相对刚度高且内聚强度低会增加 PTD 微裂纹的倾向，而降低牙本质微观结构的塑性耗散和韧性。PTD 的低韧性也会促进 PTD 的微裂纹。ITD 的大摩擦角和弱应变硬化可促进 PTD 的微裂纹，并同时提高牙本质微观结构的韧性。此外，还确定了 PTD/ITD 界面的内聚强度在控制断裂机制方面起着至关重要的作用；低内聚强度会导致界面断裂并抑制 PTD 的微裂纹，这解释了实验中观察到的裂纹沿界面偏转的现象。然而，界面的韧性对牙本质的断裂影响可以忽略不计。
