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. Materials and Methods: Ultimate tensile cohesive strengths of the DEJ region of human and bovine teeth were measured using a microtensile test, and the nanohardness and Young's modulus from deep enamel to superficial dentin of human teeth were measured using a nanoindentation tester. Results: The mean ultimate tensile cohesive strengths of bovine and human DEJ region were 47.7 MPa 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 with previous results of the bond strength of resin bonding systems indicate that current resin bonding systems might reproduce the biological adhesion of enamel to dentin in terms of the tensile strength. Moreover, the indentation properties of the DEJ region showed higher values than those of the underlying dentin or of resin impregnated dentin. [ABSTRACT FROM AUTHOR]