Nano-mechanical properties profiles across dentin-enamel junction of humanincisor teeth

Understanding how load is transferred from enamel to dentin and how the two tissues function as a single mechanical unit during mastication requires s tudies of micromechanics in relation to microstructure of the dentin-enamel junction (DEJ) zone. In this investigation, nano-hardness and elastic modu lus of human incisor teeth were studied across the DEJ. It was found that, over a length scale of about 20 mu m, there were decreasing trends in both hardness and elastic modulus across the DEJ zone profiling from enamel to d entin. Images obtained using atomic force microscopy from polished surfaces of cross-sectioned dental samples showed an interpenetrated microstructure of enamel and dentin at the DEJ zone. This result suggests that the nano-m echanical property profiles across the DEJ were due to a continuous variati on in the ratios of relative amount of enamel and dentin. These characteris tics of the DEJ zone could be significant for describing the structural and mechanical coupling of the two tissues. By increasing the contact area acr oss the interface between the two hard tissues the stresses are dissipated reducing interfacial stress concentrations at the DEJ, thereby promoting ef fective load transfer from the hard (brittle) enamel to soft (tough) dentin . (C) 2000 Elsevier Science S.A. All rights reserved.