In-situ observation of fractal structures and electrical conductivity in human tooth enamel

In this paper we present two phenomena observed in situ when human tooth enamel is heated in the transmission electron microscope. One is the deposition of hydrocarbon molecules on the enamel surface, forming fractal structures (‘bushes’), and the other is the dielectric-to-conductive transition that this material presents. The explanation of the fractal phenomenon is the reaching of an umbral energy after which an electrical field appears, producing these structures, whereas the conductivity phenomenon is a behaviour which enamel presents with increasing temperature. It seems that for the fractal phenomenon the electron beam and a high temperature are necessary elements for its appearance; for the electrical conductivity, a high temperature is the only requirement. All this opens some potential technological applications for hydroxyapatite, the principal component of tooth enamel.