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dentin
Dentin () (American English) or dentine ( or ) (British English) ((ラテン語:substantia eburnea)) is a calcified tissue of the body, and along with enamel, cementum, and pulp is one of the four major components of teeth. It is usually covered by enamel on the crown and cementum on the root and surrounds the entire pulp. By weight, 70% of dentin consists of the mineral hydroxylapatite, 20% is organic material, and 10% is water.〔 Yellow in appearance, it greatly affects the color of a tooth due to the translucency of enamel. Dentin, which is less mineralized and less brittle than enamel, is necessary for the support of enamel.〔Johnson, Clarke. "(Biology of the Human Dentition )." Page accessed July 18, 2007.〕 Dentin rates approximately 3 on the Mohs scale of mineral hardness.〔Marshall GW Jr, Marshall SJ, Kinney JH, Balooch M.J. The dentin substrate: structure and properties related to bonding ''J'' ''Dent.'' 1997 Nov;25(6):441-58.〕
Dentinal sclerosis/transparent dentin-sclerosis of primary dentin is regressive alteration in tooth characterized by calcification of dentinal tubules. It can occur as a result of injury to dentin by caries or abrasion, also manifestation of normal aging process.
==Development==
The formation of dentin, known as dentinogenesis, begins prior to the formation of enamel and is initiated by the odontoblasts of the pulp. Dentin is derived from the dental papilla of the tooth germ.〔 After apposition of predentin and maturation into dentin, the cell bodies of the odontoblasts remain in the pulp inside the tooth, along its outer wall. Unlike enamel, dentin continues to form throughout life and can be initiated in response to stimuli, such as tooth decay or attrition.
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