Hardness and indentation modulus of human enamel and dentin

Information on mechanical properties of human enamel and dentin and effect of load on their deformation and damage tolerance is very important in the development of successful dental materials. In this study, the hardness, indentation modulus and deformation characteristics of tooth have been investigated across the lingual-buccal enamel and dentin cross-section by instrumented indentation up to 1500-nm indentation depth. We realized and examined the distribution of hardness and modulus at different areas of enamel and dentin with the aim to understand deformation behaviour at these different locations. Scanning electron microscopy was used for the microstructure characterization of the enamel and dentin and their deformation behaviour. Raman spectroscopy analyses were carried out for determination of the enamel and dentin composition as well. The average values of hardness and modulus for enamel in the occlusal area are 5.35 +/- 0.19 and 98.1 +/- 1.5 GPa, in the inner area 3.68 +/- 0.5 and 81.8 +/- 5 GPa and in the area close to the dentin-enamel junction 2.83 +/- 0.27 and 71.4 +/- 4.1 GPa, respectively. The average values of hardness and modulus of dentin in the area close to the dentin-enamel junction are 0.71 +/- 0.05 and 21.27 +/- 0.76 GPa and in the inner area 0.65 +/- 0.06 and 19.79 +/- 0.93 GPa, respectively. The effect of the indentation location on deformation and mechanical properties was clarified.