An analytical ultrastructural study of the iron-rich surface layer in rat-incisor enamel

Electron-dense particles, approximately 4 nm (40 A) in diameter were present. Evidence is offered that these particles represent iron probably in the form of amorphous hydrous ferric hydroxide. From X-ray probe analytical data, it is suggested that this iron component is accommodated through the process of adsorption rather than by direct substitution of calcium and phosphorus. The iron-rich surface layer was more resistant to acid etching than subsurface enamel. Reported areas of reduced mineral density of enamel at the enamel-dentine junction appear to be preparation artifacts.