Wavelength-independent Microradiography: A Method for Non-destructive Quantification of Enamel and Dentin Mineral Concentrations using Polychromatic X-rays

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Abstract
Wavelength-independent Microradiography (WIM), described in this paper, used polychromatic, high-energy (≤ 60 kV) x-rays for determination of mineral concentrations in tooth material non-destructively. This was done with the aid of a reference step-wedge made of 94% aluminum, 6% zinc. The mass attenuation coefficient of this material has a wavelength-independent ratio to the mass attenuation coefficients of enamel and dentin. With this method, mineral concentrations of enamel and dentin samples, with a thickness up to 500 μm, were determined at 20- and at 60-kV tube voltage. The samples were demineralized for 72 and 144 h and measured again. Comparison of the data showed that mineral quantification was within 1.5%, independent of the x-rays used. Finally, these mineral concentrations-obtained from the Wavelength-independent Microradiography-were compared with measurements of the same samples by Longitudinal Microradiography. A correlation of 0.99 was found for enamel and one of 0.96 for dentin.