Trace-element content in the enamel surface and in whole enamel of deciduous incisors by proton-induced X-ray emission of children from rural and urban Finnish areas.

The absolute concentrations of Mn, Fe, Ni, Cu, Zn, Sr and Pb in whole enamel, and in labial and lingual surface enamel of deciduous incisors were determined with proton-induced X-ray emission calibrated with the International Atomic Energy Agency animal-bone standard. The differences between the mean concentration values of the 19 samples from the urban area and those of the nine samples from the rural region were not significant. The concentrations of the elements measured on the surface, depth 0-20 microns, were higher than the corresponding average values of the whole enamel by factors of 1.1-35. The lowest factor, 1.1, was for Sr and the highest, 35, for Pb. There were, however, large variations in concentration between the lingual and labial surfaces of individual teeth. Nevertheless, there were no significant differences between the mean concentrations for the labial and lingual surface, except for lead.