The use of teeth as the site for the in vivo or ex vivo quantification of skeletal strontium by energy-dispersive X-ray fluorescence spectrometry: A feasibility study

Abstract

The use of an energy-dispersive X-ray fluorescence spectrometry (EDXRF) system equipped with an ¹²⁵I source was validated for in vivo and ex vivo quantification of strontium in human teeth. The mean concentration of enamel strontium for an area with a high influx of immigration (Toronto, Ontario, Canada) is also reported. It was found that the mass attenuation of the strontium and calcium X-rays allows for a probing depth of 1.8 mm (Sr Kα) allowing the front central incisors to act as the site for the in vivo or ex vivo quantification of strontium as well as for molars to be used ex vivo for the quantification of enamel strontium. The calcium signal for all teeth studied (n = 42) was found to have a relative standard deviation of 5.7% which allowed for successful normalization of the strontium signal to that of calcium. Validation of the EDXRF method was performed on human molars (enamel thickness of (1.9 ± 0.7) mm, p < 0.05), by graphite furnace atomic absorption spectrometry (GFAAS). The EDXRF method was found to produce equivalent strontium determinations to that of GFAAS (p < 0.05). Our results also demonstrate that for a sample from a large metropolitan area, the fresh enamel strontium concentrations range from 42–301 ppm with a mean strontium concentration of (169 ± 80) ppm (p < 0.05).