Since enamel is semitranslucent, the color of dentin and any material underneath the enamel strongly affects the appearance of a tooth. At the edges of teeth where there is no dentin underlying the enamel, the color sometimes has a slightly blue or translucent off-white tone, easily observable on the upper incisors. The normal color of enamel varies from light yellow to grayish (bluish) white. In humans, enamel varies in thickness over the surface of the tooth, often thickest at the cusp, up to 2.5 mm, and thinnest at its border with the cementum at the cementoenamel junction (CEJ).
The maintenance and repair of human tooth enamel is one of the primary concerns of dentistry. Remineralisation of teeth can repair damage to the tooth to a certain degree but damage beyond that cannot be repaired by the body. Once fully formed, enamel does not contain blood vessels or nerves, and is not made of cells. Enamel is formed on the tooth while the tooth develops within the jaw bone before it erupts into the mouth. The primary mineral is hydroxyapatite, which is a crystalline calcium phosphate. Enamel is the hardest substance in the human body and contains the highest percentage of minerals (at 96%), with water and organic material composing the rest.
