Dentin (BE: dentine) is the name of substance between the enamel (crown) or cementum (root) of a tooth and the pulp chamber. The porous, yellow-hued material 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 severe caries if not properly treated.

Dentin is a mineralized connective tissue with an organic matrix of collagenous proteins. The inorganic component of dentine consists of dahllite (http://www.mindat.org/min-896.html). Dentine contains a microscopic structure called dentinal tubules which are micro-canals that radiate outward through the dentine from the pulp cavity to the exterior cementum border. These canals have different configurations in different ivories and their diameter ranges between 0.8 and 2.2 micrometres. Their length is dictated by the radius of the tooth. The three dimensional configuration of the dentinal tubules is under genetic control and is therefore a characteristic unique to the order.