Schematic diagrams of a partially formed tooth showing details of amelogenesis. a. The enamel is drawn to show the enamel rods extending from the dentinoenamel junction to the surface of the tooth. Although the full thickness of the enamel is formed, the full thickness of the dentin has not yet been established. The contour lines within the dentin show the extent to which the dentin has developed at a particular time, as labeled in the illustration. Note that the pulp cavity in the center of the tooth becomes smaller as the dentin develops. (Based on Schour I, Massler M. J Am Dent Assoc 1936;23:1948.) b. Dur ing amelogenesis, enamel formation is influenced by the path of the ameloblasts. The rod produced by the ameloblast forms in the wake of the cell. Thus, in mature enamel, the direction of the enamel rod is a record of the path taken earlier by the secretory-stage ameloblast. c. At the apical pole of the secretory-stage ameloblasts are Tomes' processes, surrounded by the developing enamel. Junctional complexes at the apical pole are also shown. Note the numerous matrix-containing secretory vesicles in the cytoplasm of the processes.
substance in the body. Amelogenins and ameloblastins are removed during enamel maturation. Thus, mature enamel contains only enamelins and tuftelins. The ameloblasts degenerate after the enamel is fully formed, at about the time of tooth eruption through the gum.
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