Investigation of Fracture-resistance of Human Teeth at the Dentin-enamel Junction Using the J-integral Calculation of Finite Element Analysis

Most human teeth have an exposed surface layer of calcified enamel, which is harder than the inner layer of dentin. The interface between the enamel and dentin is called the dentin-enamel junction (DEJ), which ensures that teeth do not collapse and fall off. The purpose of this study was to use finite element analysis software through the $J$-integral method and the extended finite element method (XFEM) to evaluate three models of DEJ structures: i) wavy DEJ with no thickness, ii) rectangle DEJ with a thickness of 0.3 mm, and iii) wavy DEJ with a thickness of 0.3 mm. This paper demonstrates that the layered structure of human teeth plays a positive role in enhancing the fracture strength and preventing the crack from spreading to the depths of teeth. At the same time, we also justify of the scalloped structure and concave orientation of the DEJ interface. The residual stresses in DEJ and its adjacent dentin region are also an important factor of tooth resistance to crack propagation. In addition, the configuration of the DEJ interface and residual stresses in DEJ & dentin areas are further justified by means of XFEM method. The findings in this study provide potential inspiration for the biomimetic design towards strengthening the dentin and dentin-like materials.