Physical properties of the dentin-enamel junction region

Purpose: To determine the physical properties between enamel and dentin at the dentin-enamel junction (DEJ) region of natural tooth structure. Materia ls and Methods: Ultimate tensile cohesive strengths of the DEJ region of hu man and bovine teeth were measured using a microtensile test, and the nanoh ardness and Young's modulus from deep enamel to superficial dentin of human teeth were measured using a nanoindentation tester. Results: The mean ulti mate tensile cohesive strengths of bovine and human DEJ region were 47.7 MP a and 51.5 MPa, respectively. The nanohardness, dynamic hardness and Young' s modulus of the DEJ region showed moderate values between those of enamel and dentin. Comparison of the cohesive strength of the human DEJ region wit h previous results of the bond strength of resin bonding systems indicate t hat current resin bonding systems might reproduce the biological adhesion o f enamel to dentin in terms of the tensile strength. Moreover, the indentat ion properties of the DEJ region showed higher values than those of the und erlying dentin or of resin impregnated dentin.