ENDOR study of irradiated tooth enamel

Semiconductor Physics, Quantum Electronics & Optoelectronics. 1999. V. 2, No 1. P.84-92. Eng. Il.: 8. Ref.: 29

g- and x-irradiated tooth enamel has been studied by EPR and ENDOR. Radiation-induced EPR spectrum of tooth enamel was found to be a superposition of signals with dominant contribution determined by CO2- radicals. Two types of these radicals were observed: ordered and disordered centers. EPR spectra of both CO2- centers are described by axial -tensor with = 1.9975 and | = 2.0021 with . The ENDOR spectrum of unannealed enamel powder consists of a singlet at Larmor frequency of 31P nuclei and doublet at Larmor frequency of 1H nuclei. Samples annealing at T = 200-250 ⁰C resulted in the destruction of disordered centers and appearence of superhyperfine structure of ENDOR spectra. Its analysis with advanced the powder ENDOR theory allows to determine the superhyperfine constants and to find for the first time that the ordered CO2- radical is located in B sites (phosphorous position) of bioapatite lattice. This substitution is accompanied by the shift of the nuclei of the first 31P shell towards the defects by 0.04 nm and the formation of the OH vacancy in the nearest radical surroundings.

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