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
Tooth whitening filling the root canal with gutta-percha points, cleaning the inside of the canal using etchant and placing a peroxide gel or sodium perborate tetrahydrate into the pulp chamber so they can work directly inside the tooth on the dentine layer. In this variation of whitening the whitening agent is sealed within the tooth over a period of some days and replaced as needed, the so-called "walking bleach" technique.. A seal should be placed over the root filling material to minimise microleakage. There is a small risk of external resorption. An alternative to the walking bleach procedure is the inside-out bleach