The origin or the development of the tooth and tissue formation is known as Odontogenisis.
The formation of the tooth begins at six weeks in the human embryo. However not all tooth develop at the same time. Although Odontogenisis is a continuous process it is divided into various stages. These stages are Bud stage, Cap stage and Bell stage which is followed by root formation and eruption. The basal layer of the ectoderm which is derived from the oral epithelium at the stomadeum undergoes proliferation both on the maxillary and mandibular arches.This however forms a horse shoe like shape of ectodermal tissue, which is the dental lamina; the ectomesenchyme which is derived from the neural crest cells surrounds the dental lamina.
The epithelial derived cells are separated from the underlying and surrounding connective tissue elements by the thin acellular layer the basement layer The Bud Stage The bud develops distally of the dental lamina on each arch. These correlate to the ten temporary teeth of each dental arches, this identifies the bud stage of tooth development. The basement membrane separates the bud from the ectomesenchyme.The ectomesenchyme cells are located deep to the bud forming clusters of cells, which is the beginning of the thickening of the ectomesenchyme. The remaining ectomesenchyme cells are grouped more or less in a uniformed manner.
The Cap Stage Cells of the inferior aspect of each tooth bud proliferate forming a larger, more expanded structure, the cap. The cap is known to be composed of an epithilially derived enamel organ, which is separated by the basement membrane, from the condensation of ectomesenchymal cells knows as dental papillaThe Bell Stage The bell stage is also termed as the differentiation stage. Mitotic activity of the enamel organ enlarges this structure and forms a new cell layer which is called the stratum intermeduim. The enlarged structure resembles a bell hence it is called the bell stage of tooth development. The cubodial cells from the previous stages start to form columnar cells which form inner enamel epithelium and outer enamel epithelium and stellate reticulum because the star shaped cells stratum intermeduim.
Towards the second stage the dental lamina breaks of and there are capillary growths up and the follicle condenses and then breaks off and goes deeper. Cytodifferentiation stage, stage of the bell stage The inner epithelial cell signals dental papilla to form odontoblast. The formed odontoblast signals the inner epithelial cells to now form ameloblast.
There dentin is formed first then enamel a little at a time.