FIGURE 2.

The principal stages of tooth formation. Thickening of the oral epithelium (blue) to form the dental lamina, the placode, bud, cap, and bell stages. The dental epithelium is shown in blue, the neural crest-derived mesenchyme in green, and all other (non-neural crest-derived) underlying mesenchyme in pink. At the cap and bell stage, the outer enamel epithelium is shown in white, the inner enamel epithelium (ameloblasts) is shown in orange, and the dentin-forming cells (odontoblasts) are shown as light brown. At the bell stage the forming enamel is yellow and the dentin dark brown. Green represents the (cranial) neural crest-derived mesenchymal cell population that migrates to the dental lamina and will eventually form the pulpal tissues seen in the bell stage.