Tooth discoloration decomposed gradually and a blue-brown discoloration develops. Teeth may turn grey following trauma-induced pulp necrosis (death of the pulp). This discoloration typically develops weeks or months after the injury and is caused by incorporation of pigments released during the breakdown of the pulpal tissue and blood into the dentin. Yellow discoloration may occur following pulp canal obliteration, i.e., the sealing up of the pulp. Trauma to a developing adult tooth (e.g., intrusion of a baby tooth into the bone) may affect the enamel layer of the adult tooth. This becomes apparent when the adult tooth erupts into the mouth. Teeth
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