The human tooth is a functionally-gradient structural composite material composed of collagen and hydroxyapatite (HAP). The outer most region is a hard enamel layer consisting primarily of HAP. Underneath is dentin region, which is composed of HAP with a significant fraction of collagen fibers. It has been demonstrated that it is possible to perform nano-indentation on sub-micron regions of tooth using either a standard nanoindentor or modified cantilever type atomic force microscope tip (AFM). In this study, we report nano-mechanical properties of dentin and enamel regions of a human tooth, measured with a nanoindentor attached to an AFM using a vertical force, in correlation with the microstructures observed with TEM.

TEM and nano-indentation samples were prepared from a juvenile human incisor tooth. The tooth was first sectioned into 1 mm thick slices along its length, each containing both dentin and enamel regions. A slice was taken to prepare a TEM sample and an adjacent slice was used for nano-indentation measurements.