Reorientable electric dipoles and cooperative phenomena in human tooth enamel

Publisher Website
Google Scholar
Abstract
A preliminary investigation of electric dipole reorientability in human tooth enamel (TE) in comparison to that in hydroxyapatite (OHAp) has been made with the fractional-polarization form of the thermally stimulated currents (TSC) method. The reorientable dipoles are the structural OH− ions. The OHAp exhibited compensation phenomena at 211.5°C and at 356°C which are associated here with the hexagonal form becoming quasi-statically stabilized and dynamically stabilized, respectively, against the monoclinic form. TE specimens were pretreated at various temperatures. All showed the onset of cooperative motions that could quasi-statically stabilize the hexagonal form at the same temperature, approximately 212°C, as did OHAp, even though the TE was already statically stabilized in the hexagonal form. Parts of the TSC spectra that did not conform to the 212°C compensation changed progressively with pretreatment temperature. Loss of incorporated H2O is identified as the most probable cause of most of these changes. This work shows considerable promise for TSC as a tool for further quantitative investigation of TE.