Human dental enamel: A natural nanotechnology masterpiece investigated by TEM and t-EBSD

The micro- and nanostructures of human dental enamel were investigated by transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). For this purpose, TEM slices were prepared from teeth by focused ion-beam milling. These slices enabled TEM and transmission-EBSD (t-EBSD) investigations to be performed, while standard EBSD on bulk tooth samples resulted only in Kikuchi patterns. On the TEM slices, t-EBSD enabled automated mapping. The TEM images and the EBSD data clearly elucidated the arrangement of the hydroxyapatite crystals on the nanometer scale. Information regarding the crystallographic orientation of the apatite grains enabled the deduction of novel nanotechnological building principles of the enamel structure based on a chain-like arrangement of the crystallites.