Spatial distribution of naturally occurring 210Po and 226Ra in children's teeth

Deciduous and permanent teeth extracted from juveniles for orthodontic purposes have been analysed using alpha-sensitive plastic track detectors for the spatial distribution of total alpha-activity and naturally occurring 210Pb-supported 210Po and 226Ra. The distribution of these radionuclides is non-uniform, with 210Po being primarily associated with outer enamel and 226Ra with the pulp. The observations suggest that 210Pb/210Po concentrates at the interface of enamel with saliva or blood, by means of unidirectional ionic exchange with calcium. In contrast, 226Ra concentrates in the predentine band at the interface with pulp and with systemic blood circulation, where its uptake is permitted by the incomplete calcification in this band. Activity concentration was measured in 900 teeth. Total concentration on the outer enamel surface of deciduous teeth, permanent teeth from children < or = 10 years and permanent teeth from children > 10 years give respective mean values of 8.63 +/- 0.26, 5.76 +/- 0.48 and 7.00 +/- 0.15 Bq kg-1. 226Ra concentration on the corresponding longitudinal sections comprising pulp, dentine and annular enamel give respective mean values of 0.715 +/- 0.055, 0.418 +/- 0.083 and 0.514 +/- 0.029 Bq kg-1. Mean activity concentration in 32 foetal teeth was 2.05 +/- 0.31 Bq kg-1. The results form the basis of more detailed studies of (1) age-dependent uptake of alpha-radionuclides in teeth and their microdistribution, and (2) the geographical variation in activity concentration with respect to environmental factors such as domestic radon exposure.