Using electron microprobe analysis, the surface layer of enamel of rat maxillary incisors was found to contain 10–30% Fe. The Ca and P concentrations in different areas of the enamel surface varied inversely with the Fe concentration. The Ca/P weight ratio was 1.8 in areas containing 10% Fe, but decreased to 1.0 in the most Fe-rich areas. The Fe concentration was highest at the prism boundaries, whereas the maximum concentrations of Ca and P were found within the enamel prisms. The concentrations of Fe in rat incisor enamel are among the highest values reported for any mineralized tissue.
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