The arrangement of ameloblasts on the surface of maturing enamel of the rat incisor tooth.

The location of striated border cells versus non-striated border cells during enamel maturation in the rat incisor was studied by light microscopy. Serial cross sections of the lower incisors were examined from a segment of the incisor in sections which also included the first molar tooth. In the series recorded here every cross section showed both striated and non-striated border cells. A map showing the distribution of cells on the enamel surface, as plotted from their position in each of the cross sections, reveals that the non-striated border cells traverse the enamel as oblique bands. Between the narrow bands of non-striated border cells were wide bands of striated border cells. The non-striated border cells were joined at their basal nuclear poles by contacts which appeared to separate the lateral inter-ameloblast space from the space between the papillary-ridge cells. Neither the striated border cells nor the non-striated border cells went entirely to the edge of the enamel organs. The above pattern of striated border cells and non-striated border cells is regarded to be a manifestation of the cyclical activity of maturation ameloblasts.