Dentin () (American English) or dentine ( or ) (British English) (Latin: 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 volume, 45% of dentin consists of the mineral hydroxyapatite, 33% is organic material, and 22% 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. Dentin rates approximately 3 on the Mohs scale of mineral hardness. There are two main characteristics which distinguish dentin from enamel: firstly, dentin forms throughout life; secondly, dentin is sensitive: 125  and can become hypersensitive to changes in temperature due to the sensory function of odontoblasts, especially when enamel recedes and dentin channels become exposed. Dentinal sclerosis
Dentinal sclerosis or transparent dentin sclerosis of primary dentin is a change in the structure of teeth characterized by calcification of dentinal tubules. It can occur as a result of injury to dentin by caries or abrasion, or as part of the normal aging process. Development
Prior to enamel formation, dentine formation begins through a process known as dentinogenesis, and this process continues throughout a persons life even after the tooth has fully developed.
Fibrofolliculomas are 2 to 4 mm in diameter, dome-shaped, yellowish or skin-colored papules usually located on the head, neck, and upper trunk. They are characteristically seen in Birt–Hogg–Dubé syndrome. : 674

See also
List of cutaneous conditions
List of cutaneous neoplasms associated with systemic syndromes
Trichodiscoma


== References ==