Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai Institute of Applied Mathematics and Mechanics, School of Mechanics and Engineering Science, Shanghai University, Shanghai 200444, China.
QianWeiChang College, Shanghai University, Shanghai 200444, China.
J Biomech Eng. 2024 Dec 1;146(12). doi: 10.1115/1.4066286.
Dentin is a biological composite exhibiting multilevel hierarchical structure, which confers excellent damage tolerance to this tissue. Despite the progress in characterization of fracture behavior of dentin, the contribution of composite structure consisting of peritubular dentin (PTD), intertubular dentin (ITD) and tubules to fracture resistance remains elusive. In this study, calculations are carried out for energy release rate associated with crack propagation in the microstructure of dentin. Crack penetration and deflection at the PTD-ITD interface are accounted for in the numerical analyses. It is found that high stiffness of the PTD plays a role in increasing crack driving force, promoting crack growth in the microstructure of dentin. For crack penetration across the PTD-ITD interface, the crack driving force increases with increasing tubule radius; and thick PTD generates amplified crack driving force, thereby leading to weak fracture resistance. The driving force for crack deflection increases with the increase in tubule radius in the case of short cracks, while for long cracks, there is a decrease in driving force with increasing tubule radius. Furthermore, we show that the competition between crack penetration and deflection at the PTD-ITD interface is controlled by the ratio of PTD to ITD elastic modulus, tubule radius and thickness of PTD. High PTD stiffness can increase the propensity of crack deflection. The microstructure of dentin with large tubule radius favors crack deflection and thick PTD is beneficial for crack penetration.
牙本质是一种具有多层次结构的生物复合材料，这种结构使其具有出色的耐损伤能力。尽管人们在牙本质断裂行为的特性研究方面已经取得了进展，但对于由管周牙本质（PTD）、管间牙本质（ITD）和牙本质小管组成的复合材料结构对断裂阻力的贡献仍然难以捉摸。在本研究中，对与牙本质微结构中裂纹扩展相关的能量释放率进行了计算。在数值分析中考虑了 PTD-ITD 界面处的裂纹穿透和偏转。结果表明，PTD 的高刚度在增加裂纹驱动力方面发挥了作用，促进了牙本质微结构中的裂纹扩展。对于穿透 PTD-ITD 界面的裂纹，随着管半径的增加，裂纹驱动力增加；而厚的 PTD 会产生放大的裂纹驱动力，从而导致断裂阻力降低。对于短裂纹，当管半径增加时，裂纹偏转的驱动力增加，而对于长裂纹，随着管半径的增加，驱动力会减小。此外，我们表明，PTD-ITD 界面处的裂纹穿透和偏转之间的竞争受 PTD 与 ITD 弹性模量之比、管半径和 PTD 厚度控制。高 PTD 刚度会增加裂纹偏转的倾向。具有大管半径的牙本质微结构有利于裂纹偏转，而厚的 PTD 有利于裂纹穿透。
