ATOMIC-FORCE MICROSCOPE MEASUREMENTS OF THE HARDNESS AND ELASTICITY OF PERITUBULAR AND INTERTUBULAR HUMAN DENTIN

An atomic force microscope was used to measure the hardness and elasti city of fully-hydrated peritubular and intertubular human dentin. The standard silicon nitride AFM tip and silicon cantilever assembly were replaced with a diamond tip and stainless steel cantilever having sign ificantly higher stiffness. Hardness was measured as the ratio of the applied force to the projected indentation area for indentations with depths from 10-20 nm. The sample stiffness was measured by imaging spe cimens in a force-modulated mode. Hardness values of 2.3 +/- 0.3 GPa a nd 0.5 +/- 0.1 GPa were measured for the peritubular and intertubular dentin, respectively. Stiffness imaging revealed that the elastic modu lus of the peritubular dentin was spatially homogeneous; whereas, ther e was considerable spatial variation in the elasticity of the intertub ular dentin. The atomic force microscope can be used to measure the me chanical properties of fully hydrated calcified tissues at the submicr on level of spatial resolution, thus augmenting more traditional depth sensing probes.