An EPR study of intact and powdered human tooth enamel dried at 400 degrees C.

An EPR study of human tooth enamel dried at 400 degrees C is presented. Enamel blocks as well as powdered samples were investigated. The discussion deals mainly with three different spectral components, i.e., a CO3(3-) and two different CO2- signals. Using the anisotropic enamel block spectra, a convincing differentiation between the latter two radicals was possible. The first CO2- signal shows no dependence on the orientation of the enamel blocks, disappears from the spectrum upon heating, and was assigned to a surface radical. The second CO2- component is mainly responsible for the angular variation of the enamel blocks and is assigned to a bulk position. For the CO3(3-) ion, the (pseudo) angular variation of its isolated spectrum is presented and discussed. By means of the results presented in this study, earlier interpretation problems are considerably reduced.