Analysis of crack interacting with the composite microstructure of dentin

Dentin possesses strong fracture resistance, which is attributed to various toughening mechanisms associated with its unique hierarchical structure. In this study, the effects of microstructural features on crack growth in dentin are analyzed. A plasticity model incorporating a local fracture criterion is used to model the mechanical behavior of intertubular dentin (ITD), and a brittle cracking model is used for the peritubular dentin (PTD). Computational simulations of fracture behavior of microstructured dentin are performed, showing that crack growth in microstructured dentin is accompanied by microcracking of PTD ahead of the primary crack, and that fracture of dentin is caused by the merging of the primary crack and microcracks nucleating in PTD. It is identified that the decrease in tubule radius and PTD thickness can lead to the development of a significant degree of microcracking in PTD, thereby enhancing toughness. We further reveal that the toughness of microstructured dentin is dependent on tubule density. The transition in fracture mechanism from multiple void interactions to crack-void interaction occurs as the tubule density decreases, which promotes toughness of dentin. In addition, the effect of the arrangement of dentin tubules is also discussed. The findings of this study provide a mechanistic insight into the region dependent fracture behavior of dentin.