Enamel is the hardest and most highly mineralized substance of the body.
Enamel is the part of the tooth that is normally seen and is supported by underlying dentin. Ninety-six percent of enamel consists of mineral, with water and organic material composing the rest. The normal color of enamel varies from light yellow to grayish white.
Enamel's primary mineral is crystalline calcium phosphate. The large amount of minerals in enamel accounts its strength.
Dentin is the tissue between enamel or cementum and the pulp chamber. It is secreted by the odontoblasts of the dental pulp. Dentin is a mineralized connective tissue with an organic matrix of collagenous proteins. Dentin is made up of 70% inorganic materials, 20% organic materials, and 10% water. Because it is softer than enamel, it decays more rapidly and is subject to cavities if not properly treated.
Cementum is a specialized bony substance covering the root of a tooth. It is approximately 45% inorganic material (mainly hydroxyapatite), 33% organic material (mainly collagen) and 22% water. The principal role of cementum is to serve as a medium by which the periodontal ligaments can attach to the tooth for stability.
The dental pulp or root canal, is the central part of the tooth filled with soft connective tissue. This tissue contains blood vessels and nerves that enter the tooth from a hole at the apex of the root. The pulp is commonly called "the nerve" of the tooth.