Electron microscopic studies on the potential loss of crystallites from routinely processed sections of young enamel in the rat incisor.

Newly formed rat incisor enamel was fixed aqueously by perfusion with glutaraldehyde and anhydrously by immersion in ethylene glycol. Ultrathin sections were studied using transmission electron microscopy and electron diffraction. Aqueously processed enamel was shown to lose its mineral content when sectioned on distilled water. This mineral loss was minimized by limiting the exposure of sections to the water. In such preparations, enamel crystallites were seen by virtue of their intrinsic electron density only. Selected area electron diffraction provided corroborative evidence for the presence or absence of crystallites in the sections. Observations on mineralized sections and on stained mineralized and distilled-water-demineralized sections revealed organic material apparently in the same location as the crystallites. Anhydrously processed enamel which was sectioned on ethylene glycol showed a similar appearance of the crystallites. This appearance was not obviously altered after staining despite evidence that organelles in the ameloblasts were stained. In view of the observations that both methods yielded similar crystallite morphology, it was concluded that aqueous techniques can be used to study the relationship between organic and inorganic components. However, valid description of crystallites in such preparations requires minimal exposure of ultrathin sections to water.