Scanning electron microscopy of developing deciduous tooth enamel.

Abstract

Structural details of the surface of the developing deciduous tooth enamel were studied under the scanning electron microscope using materials from human fetuses ranging in age from 6 to 8 months. The excised dental germs were fixed either in 2.5% glutaraldehyde or 10% neutral formalin solution. In a number of specimens fixed, treatment by 1:2 diamino-ethane was conducted to remove organic materials from the surface of enamel.1. The surface of developing enamel appeared to consist of a regular arrangement of depressions, each of which was concave due to the formation of the interrod portion which always preceded that of th rod ends. The size and depth of these depressions varied according to the stage of enamel development.2. In immature stages of enamel development the depressions were always deeper than those seen in the mature enamel and showed either tapared cylindrical or wedgelike forms. The floor of the depressions were rough-surfaced, being covered by particles smaller than 100mμ in diameter. On the walls of the depressions there were numerous structures of varying size acicular to columnar in form. Many depressions also contained other structures, such as spherical granules and amorphous lumps. In the specimens treated with organic solvent these structures had almost disappeared. Instead, there were crystalline structures of enamel matrix, most of which had the appearance of well defined flakes in relief.3. It was demonstrated by an electron microanalyser that the Ca concentration in the rod ends in immature stages of enamel development was much higher than that in interrod portions.4. In the boundary zone between immature and mature enamel the depressions became considerably shallower and showed a more flattened floor.5. The surface of mature enamel lacked even the shallowest kind of depressions as observed in the boundary zone, and there was seen only undulation of very slight concavities and elevations arranged alternately.