title: Electron paramagnetic resonance of human tooth enamel at high gamma ray doses.
abstract: Powdered human tooth enamel was exposed to 60Co gamma rays up to a dose of 100 kGy. The electron paramagnetic resonance (EPR) signal intensity (1) of the radiation-generated carbon dioxide radicals was measured for dependence on absorbed dose (D). The EPR dose response can be fitted with an exponential saturation function I = I(M)[1 - exp(-D/D37)] with the saturated signal intensity (I(M)) and the dose saturation value (D37). The obtained value D37 = 9.64 (+/- 0.96) kGy (measured at least one month after irradiation) exceeds those given in the literature. The saturated concentration of orthorhombic CO2- radicals was estimated at 6.5 x 10(17) per gram of enamel by comparing the integrated EPR spectra of enamel and a standard MgO:Cr probe. For enamel samples, which were heated before irradiation for one hour at +405 degrees C, the value of D37T = 3.89 (+/- 0.44) kGy and the saturated value of CO2- radicals 3.4 x 10(17) per gram of enamel were lower than for unheated samples. The initial rise of the signal with the dose was slightly higher (8.8 x 10(13) radicals/g x Gy) for heated compared with unheated samples (6.8 x 10(13) radicals/g x Gy).
authors.affiliation: National Institute of Chemical Physics and Biophysics, Tallinn, Estonia. gli@kbfi.ee
authors.forename: G
authors.initials: G
authors.lastname: Liidja
authors.forename: A
authors.initials: A
authors.lastname: Wieser
mesh_terms: D003037:Cobalt Radioisotopes; D003743:Dental Enamel / Q000033:anatomy & histology / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D005720:Gamma Rays; D006801:Humans; D066298:In Vitro Techniques; D008964:Molar, Third
chemical_list: D003037:Cobalt Radioisotopes