Human tooth development are known as outer enamel epithelium (OEE). The columnar cells of the enamel organ adjacent to the enamel papilla are known as inner enamel epithelium (IEE). The cells between the IEE and the stellate reticulum form a layer known as the stratum intermedium. The rim of the enamel organ where the outer and inner enamel epithelium join is called the "cervical loop". In summary, the layers in order of innermost to outermost consist of dentin, enamel (formed by IEE, or 'ameloblasts', as they move outwards/upwards), inner enamel epithelium and stratum intermedium (stratified cells that support the synthetic activity of the
Human tooth permanent teeth begin to form in the twentieth week. If teeth do not start to develop at or near these times, they will not develop at all. A significant amount of research has focused on determining the processes that initiate tooth development. It is widely accepted that there is a factor within the tissues of the first pharyngeal arch that is necessary for the development of teeth. Tooth development is commonly divided into the following stages: the bud stage, the cap, the bell, and finally maturation. The staging of tooth development is an attempt to categorize changes that take place