A tooth bud is a mass of tissue that can eventually form the parts of a tooth. Every tooth passes through three developmental stages: growth calcification and eruption.
By the seventh week of fetal development epithelium cells skin cells of the mouth thicken along the ridge of the developing jaws. The epithelium cells eventually form the dental lamina a horseshoe-shaped band in the mouth. At this point the growth period begins. The growth period is divided into three stages: bud cap and bell. Tooth buds are the patches of epithelial cells that eventually grow into underlying tissues. Tooth buds for the primary teeth develop as soon as the dental lamina is formed. Typically each dental arch contains ten tooth buds that will eventually spawn the primary teeth. Tooth buds for the permanent teeth develop from the seventeenth week of fetal development until the age of five. When the permanent teeth are ready to erupt the primary teeth will undergo a process called exfoliation or shedding. The root of the primary tooth will weaken or resorb until the primary tooth falls out.
The cap stage the second stage of growth is also known as proliferation reproduction or multiplication. As the cells of the tooth grow the tooth bud takes the shape of a cap. The area underneath the cap is called the dental papilla. In the final stage the bell stage (also called histodifferentiation) the epithelium of the cap will form the enamel the hard white outer layer of the tooth. The dental papilla will form the dentin cementum and the pulp. The dentin is the internal layer of the tooth the cementum is the bony tissue covering the root of the tooth and the pulp is the soft inner part of a tooth. At this stage the tooth undergoes morphodifferentiationﾗthat is it takes on the shape and form of a tooth.
The next stage of tooth development is calcification. At this point the tooth bud has already taken on the shape of a tooth. Now deposits of calcium and mineral salts harden the tooth tissue. Next layers of enamel form the tooth from the top of the crown down.
The final stage eruption refers to the upward movement of the tooth into its assigned position in the mouth. Once the tooth crown has formed the root begins to develop triggering eruption. For permanent teeth about three years elapse between the time of crown completion and the time of tooth emergence.