Ultrastructure of Striations in Carious Human Enamel

Abstract

A correlated microradiographic-transmission electron microscopic study examined incipient caries in human enamel from the enamel surface through the body of the lesion. In sections parallel to enamel prisms in the body of the lesion, cross-striations are accentuated as 3–4 μm wide, light and dark bands. In the more radiolucent striations, crystals are reduced in number as well as in length with some showing longitudinal splitting. In sections with prisms cut in cross-section, most crystals exhibit central dissolution except for isometric hexagonal crystals bordering a gap at the prism periphery. Eventually a complete loss of crystals from prism cores occurs. Asymmetric widening of the gap at the prism borders may be associated with the striae of Retzius. Possible causes for differences in the rate of crystal dissolution in alternating striations are discussed.