Structure of Sorex (Insectivora) enamel.

Abstract

The enamel pigmentation of Sorex (Insectivora) is distributed over the whole of the tooth from the enamel surface to the zone of the middle enamel layer, except for some unpigmented micro-areas. With respect to the structure of the enamel, Sorex has two types of organization in the unpigmented enamel (UE) and pigmented enamel (PE); prismatic and prismless enamel or tubular and atubular enamel types. In the UE areas, the enamel prisms run in a relatively complex but systematic way. However, on the PE, the enamel prisms run almost parallel to the enamel surface.The enamel pigmentation is caused by iron. The X-ray micro-diffraction pattern suggests that the apatite of the PE is similar to that of the UE. The electron-diffraction pattern shows that the length of the axis of PE apatite is slightly different from that of natural apatite crystallites, and many dislocations were observed in PE crystals in high-resolution electron micrographs. These results suggest that some iron atoms may be distributed not only between but also inside the crystallites. The iron content is about 8% (by weight) of the enamel, as shown by SEM electron-probe microanalysis.