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The aim of the present study was to examine in detail, both at light and electron microscopical levels, the morphological variations in ameloblast of the fetal rat incisor enamel organ. Rats were started on distilled water at the beginning of pregnancy. The pups were sacrificed 11 days after delivery and the animals were perfused intravascularly with glutaraldehyde and the incisors were removed. To examine on the ultrastructure of the ameloblast, the study employed primary light microscopy but electron microscopy was used to clarify some of the light microscopic findings. Longitudinal sections through the incisors of a show continuous layer of ameloblasts on the labial surface of the teeth. This layer contains the entire sequence of developmental stages in enamel production. The ameloblast layer was divided into three main zones : 1) Presecretory zone, region of ameloblasts facing pulp. 2) Secretory zone, region of inner and outer enamel secretion. 3) Maturation zone, region of reduced ameloblasts. In particularly, the present study has shown that two distinctively different types of ameloblasts appear in the enamel organ during enamel maturation in the rat incisors. These two types have been designated ruffle-ended ameloblasts(rAB) and smooth-ended ameloblasts(sAB).
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