Grain Size Effect of Tooth Enamel to Electron Paramagnetic Resonance Spectrum

Abstract

Electron Paramagnetic Resonance (EPR) spectroscopy is one of the methods applicable to retrospective dosimetry. The retrospective dosimetry is a part of dose reconstruction for estimation of exposed dose occurred years before the estimation. As a biosample, tooth enamel is known as to show good sensitivity to the absorbed dose and is widely used. Since the later 1980s, EPR dosimetry with tooth enamel has been studied and applied for the retrospective dosimetry. There are some factors affecting the sensitivity of enamel to absorbed dose. One of the factors is a size of enamel. Grain size of the 1.0 mm -0.1 mm range is commonly used and 0.60 mm ~ 0.25 mm is recommended in other study. But the sensitivity can be varied by the grain size. In this study, the granular effect of enamel to the sensitivity of EPR spectrum is examined. To verify the effect, 15 teeth were used for the enamel separation. In the enamel separation, to minimize the physically induced EPR spectrum, only chemical separation method was used. Separated enamels were divided by their size. The sizes of each sample are 1.0 mm ~ 0.7 mm, 0.7 mm - 0.5 mm, 0.5 mm ~ 0.3 mm, 0.3 mm ~ 0.1mm and below 0.1 mm, respectively. All enamel samples show EPR spectrum related to the absorbed dose and the EPR spectrum shows linearity to the absorbed dose. The sensitivities are similar for each sample. But the enamel of size below 0.1 mm shows poor characteristics relative to other enamel size. So, it is not recommended to use enamel samples below 0.1 mm.