Strontium metabolism in teeth and enamel dose assessment: analysis of the Techa river data

Abstract

People living on the banks of the Techa river were exposed to 90Sr in the early 1950s. Data obtained by radiochemical measurements of extracted permanent teeth, 90Sr autopsy measurements in bone and tooth samples, in vivo measurements of surface beta activity of the anterior teeth and whole-body counter (WBC) measurements of 90Sr in the skeleton have been analyzed. Surface beta activity measurements indicate a biological half-life of 90Sr of about 35 years in enamel. The WBC measurements have been performed since 1974 and a model for the age-dependent strontium retention in human bone has been used to extrapolate to previous time periods when the other measurement results were obtained. For the first decade after the intake, the ratio of the 90Sr concentrations in teeth and bones were found to decrease with age at the time of major intake, from about 10 for 1-year-old children to about 0.3 for adults. There was a considerable variability of individual data within each age group. For adults, the correlation between 90Sr in skeleton and teeth was not high at 0.47 according to radiochemical data for posterior teeth (molars and premolars) and 0.43 according to measurements of surface beta activity for anterior teeth. For children and adolescents there was no correlation between individual measurements in the skeleton and teeth. The absorbed dose in enamel due to 90Sr in dentine has been calculated by Monte Carlo simulations of the electron transport. The results are in agreement with EPR measurements of the absorbed dose in the enamel of persons exposed, mainly due to 90Sr ingestion.

EPR dosimetry with tooth enamel: A review

“…Gy in the teeth that had already been completed at that time (Tolstykh et al, 2000;Romanyukha et al, 2001). Because of the differences in the development processes of teeth in different buccal positions, incorporation of radioisotopes into teeth of different types occurs at different ages.…”

“…These factors make the volume-averaged dose provided by EPR measurements of little significance for short-range particles. Tolstykh et al (2000Tolstykh et al ( , 2003 argued against the suitability of EPR dosimetry with 90 Sr contaminated teeth, in particular because the estimate of the tooth enamel dose should account for the time dependence of the 90 Sr content and distribution not only in enamel, but also, and especially, in dentine. They concluded that EPR tooth enamel dosimetry should be limited to the assessment of the external dose component.…”

“…When the radioactivity level is sufficiently high, the volume-averaged 90 Sr concentration can be obtained by the traditional in vivo tooth β−counters and in vitro radiochemical methods (Tolstykh et al, 2000); otherwise, it can be measured by a low-background β−counting set, such as used by Tikunov et al (2006). Distribution of the β-emitting radionuclide concentration can be mapped with two methods: thin TLD (Goksu et al, 2002) and photostimulable phosphor imaging plates (Romanyukha et al, 2002b;Shishkina et al, 2002 Sr incorporated in dentine Tolstykh et al 2000), in jaw bone, and tooth enamel itself (Tolstykh et al 2000).…”

“…Distribution of the β-emitting radionuclide concentration can be mapped with two methods: thin TLD (Goksu et al, 2002) and photostimulable phosphor imaging plates (Romanyukha et al, 2002b;Shishkina et al, 2002 Sr incorporated in dentine Tolstykh et al 2000), in jaw bone, and tooth enamel itself (Tolstykh et al 2000). They used different Monte Carlo codes and made different assumptions of the 90 Sr deposition in the tissue sources.…”

“…The model proposed in the paper by Tolstykh et al (2000) and its upgraded versions (Shved and Shishkina, 2000;Shishkina et al, 2001a) was more sophisticated. The tooth was modelled as a set of coaxial cylindrical layers, each of its own composition, which described the various tissues of a tooth (root dentine, cementum, alveolar bone, pulp, crown dentine, tooth enamel and the enamel of the neighboring teeth).…”