An electron microprobe investigation of the distribution of iron in rat incisor enamel

Abstract

abstract – Maxillary incisors from six five‐month‐old rats were studied with thc electron microprobe. Analysis of enamel in the pigmented portion of the teeth revealed a zone of high iron content extending 15–20 microns from the enamel surface. From a maximum of 10.1% (range 8.8–12.6%) close to the enamel surface, the iron concentration gradually decreased over a distance of 10 microns to less than 0.1%. At the point of maximum iron concentration the calcium content averaged 28.2% and the phosphorus content 15.7%. The concentrations of these elements increased gradually from the enamel surface and reached a plateau of approximately 34% calcium and 17% phosphorus at a point where the concentration of iron had decreased to a minimal Ievel. The mean Ca/P weight ratio in the zone of maximum iron content was 1.80 and differed significantly from the Ca/P ratio of 1.98 of the enamel beneath the pigmented zone. The zone of raised iron concentration coincided with the extension of the pigmented zone of the enamel. Apically to the pigment incorporation zone, the enamel contained less than 0.1% iron in the surface layer as well as in deeper layers.