Tooth enamel is the hardest and most highly mineralized substance of the body, and with dentin, cementum, and dental pulp is one of the four major parts of the tooth. It is the normally visible dental tissue of a tooth and must be supported by underlying dentin. Ninety-six per cent of enamel consists of minerals, with water and organic material composing the rest. The normal color of enamel varies from light yellow to grayish white. At the edges of teeth where there is no dentin underlying the enamel, the color sometimes has a slightly blue tone. Since enamel is semitranslucent, the color of dentin and any restorative dental material underneath the enamel strongly affects the appearance of a tooth. Enamel varies in thickness over the surface of the tooth and is often thickest at the cusp, up to 2.5 mm, and thinnest at its border, which is seen clinically as the cementoenamel junction (CEJ).
Enamel's primary mineral is hydroxyapatite, which is a crystalline calcium phosphate. The large amount of minerals in enamel accounts not only for its strength but also for its brittleness. Dentin, which is less mineralized and less brittle, compensates for enamel and is necessary as a support. (More...)