Enamel is outermost layer of the tooth, which lies above dentin. The enamel is a tissue with a 96% mineral content and 4% organic material and water. The inorganic content of the enamel is a crystalline calcium phosphate, hydroxyapatite, which is also found in bone, calcified cartilage, dentin and cementum.
The dissolution of the hydroxyapatite crystals by the action of acids is the cause of dental caries. The chemical nature of the organic material has not been fully elucidated, but it is considered to be of a proteic nature and to contain some polysaccharide material.
Due to its high mineral content, the enamel is hard tissue, this property enables it to withstand the mechanical forces acting upon enamel. The enamel is transparent in nature and have a color that varies from a light yellow to greish white.
Among all the layers of the tooth, Enamel is hardest layer. It is as hard as lightweight steel.