Artefacts of electron paramagnetic resonance dosimetry caused by a mechanical effect on samples of tooth enamel

It has been ascertained that in the process of the mechanical preparation of tooth enamel, two types of paramagnetic centres are formed. The centres of one type, the long-lived ones, occurred in the process of friction of dental borers against the enamel. Their number grew with an increase of the treated surface area and the rotation rate of the borers. The electron paramagnetic resonance signal of such radicals looked like a symmetric singlet with the width deltaHpp=0.094 mT and g=2.0029. The other, short-lived centres, occurred when tooth enamel was crushed into small granules, which caused an increase in the background signal intensity. The mechanism of formation of paramagnetic centres in enamel during the process of teeth treatment and prepartion has been considered. The estimation of an increase in the reconstructed absorbed dose due to the contribution from the mechanically induced signal has been made. Contamination of tooth enamel samples with diamond crumb during diamond borer preparation has been shown to lead to an imaginary increase in radiation-induced signal intensity and, consequently, to an increase in the reconstructed dose.