X-Ray Attenuation and X-ray Fluorescence Measurements of a Primary Incisor Tooth Slice*

Primary teeth are accessible human tissues whose analysis can reveal developmental health issues such as toxic exposures, malnutrition, and dietary changes. X-ray fluorescence (XRF) elemental analysis is nondestructive, fast, and inexpensive. Modern table-top systems can probe microscopic elemental distributions and may become a viable alternative to synchrotron-based studies. A primary incisor tooth was cleaned by sonication in distilled water for 2-3 hours, embedded in resin, and cut in thin slices with a diamond saw blade. A 0.63 mm-thick slice was selected for analysis by the microbeam from an integrated polycapillary x-ray lens and x-ray tube unit. XRF and linear attenuation coefficient (μ) measurements consisted of photon energy spectra acquired by an x-ray detector in backscatter and transmission geometries, respectively. A linear scan of 0.05 mm steps measured μ of dentin, enamel-dentin junction, and enamel regions. Two locations in the dentin and enamel layers were probed by XRF. Average μ values for photon energy range 9.6-15.5 keV, were in the 0.59 to 5.3 mm^-1, and 2.0 to 9.8 mm^-1 ranges for dentin and enamel, respectively. These results are consistent with reported density differences: 1.8-2.1 g/cm³ for dentin and 2.6-3.0 g/cm³ for enamel, as well as enamel’s higher Ca and P content. The fundamental parameter method was applied to convert XRF measurements into concentrations. In dentin, P, Ca, Cu, Zn, and Sr concentrations in mg/g units were estimated to be 140±40, 157±3, 1.76±0.05, 0.18±0.02, and 0.026±0.003, respectively. In enamel, the same elemental concentrations in mg/g were 80±30, 168±3, 0.70±0.05, 0.57±0.03, and 0.015±0.002, respectively. Sr/Ca ratios agreed with reported measurements, but Zn/Ca ratios were 10 times larger. This result is consistent with past observations of Zn and Cu XRF peaks from metallic parts of the experimental setup. Future work will further investigate the accuracy of XRF results and subtraction of XRF signals not originating in the sample.