Mineral content of developing rat incisor enamel

ABSTRACT – The contents of Ca and P in developing enamel of the continuously growing rat incisor were examined by the electron microprobe. A longitudinally sectioned, epoxy res-in-embedded maxillary incisor from a 5-month-old rat was analyzed by linear scans across the enamel at intervals from the growing end. Near the growing end, concentrations of approximately 2 % Ca and 1 % P were found close to the ameloblast-enamel junction, increasing to 18 % Ca and 9 % P near the dentino-enamel junction. With increasing distance from the growing end, a successive increase of the mineral content was observed, together with a leveling out of the concentration gradients from the enamel surface to the amelo-dentinal junction seen at earlier stages of mineralization. Mature enamel contained about 35 % Ca and 17 % P. The results were discussed in the light of previous electron microscopic observations of the same specimen material. It was concluded that in analysis of mineralized tissues in an early stage of development, the mineral content as found by the electron microprobe technique can be considered a valid approximation of the true situation. This technique may also be applied to the study of hard tissues in varying stages of demineralization.