Cementum

This is a thin, light yellow layer of bonelike tissue that covers the roots of the teeth. Its main function is to anchor teeth to the bony walls of the tooth sockets in the periodontium by attaching to the periodontal ligament. The cementum is composed of approximately 55% organic material and 45% inorganic material, mainly calcium salts. It joins the enamel at the cervix of the tooth at the cementoenamel junction. In most teeth, the cementum overlaps the enamel for a short distance; in some, enamel meets the cementum in a sharp line; and in a few teeth, there is a gap between the enamel and the cementum, exposing a narrow area of root dentin. Such areas may be very sensitive to thermal, chemical, or mechanical stimuli. Cementum is formed continuously to make up for the loss of tissue due to wear, and to allow for the attachment of new fibers of the periodontal ligament to the surface of the root.9