stages). The interaction and signalling between the enamel organ and the surrounding mesenchymal cells play an important role in the later stages of tooth development. Each dental arch will have 10 tooth buds, accounting for 20 primary teeth. Cap Stage The cap stage occurs in week 9-10 i.u. Unequal proliferation of cells during this stage, invaginating into the ectomesenchyme tissue, leads to the formation of the cap-shaped enamel organ. The ectomesenchyme tissue also invaginates superficially to shape the primitive dental pulp. Differentiation of cells occurs at this stage to make different tissue layers; external enamel epithelium, stratum intermedium, stellate reticulum, internal enamel epithelium, dental papilla, and dental follicle. The external enamel epithelium, a layer of simple cuboidal epithelium, has a protective role during tooth development. The stellate reticulum, the innermost layer of the enamel organ, gathers GAGs between cells. The internal enamel epithelium will form enamel during the Bell Stage Early Bell stage There is uneven growth of enamel organ in this phase, and the epithelial cap deepens. The cap shape of the enamel organ assumes a bell shape as the undersurface of the cap deepens. Foldings of the internal enamel epithelium (done by the growing papilla cells) maps out the occlusal pattern of the tooth crown. The process is known as morphodifferentiation. The pressure exerted by the dental papilla cells has been shown to be opposed equally by the pressure from the fluid in the stellate reticulum (present in the enamel organ). The folding of the enamel organ is caused by different rates of mitosis and difference in cell differentiation times, causing different crown shapes in each tooth. Late Bell stage This stage is the apposition stage (formation of dental hard tissues), also characterised by the commencement of root formation and mineralisation. The area between the internal enamel epithelium and odontoblasts outline the future dentinoenamel junction. Formation of dentine (dentinogenesis) precedes enamel formation (amelogenesis). It occurs first as along the future dentinoenamel junction in the region of future cusps and proceeds pulpally and apically. Cells of the internal enamel epithelium become pre-ameloblasts and release inductive factors which encourage the differentiation of odontoblasts from the mesenchymal cells of the dental papilla. This can be seen in the figure (marked A). The odontoblasts lay down dentine (see pale blue band). After the first layer of dentine is formed, this induces ameloblasts (B) to lay down enamel (red region) over the dentine