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Congenital or Developmental, continued
Developmental Tooth Defects
Hypoplasia: A condition of arrested development in which an organ or part of an organ remains below the normal size or in an immature state.
hypoplasia can result from a number of environmental insults during development, including infection, toxins (eg, lead or mercury), fluoride, medications, and prematurity. (Refer to Chapter 2: Dental Development and Chapter 12: Systemic Disease for more information.)
Inherited enamel defects include
Amelogenesis Imperfecta: Faulty development of tooth enamel that is genetically determined.
Amelogenesis Imperfecta. There are 4 genetically distinct types of this inherited condition (often autosomal dominant) that result in hypoplastic and hypocalcified enamel, which appears yellow or brown and is easily worn away.
Dentin: A calcareous material similar to bone but harder and denser that composes the principal mass of a tooth; consists of a matrix containing minute parallel tubules which open into the pulp cavity and during life contain processes of the cells of the pulp.
dentin defects include several types of Dentinogenesis Imperfecta and dentin dysplasia, which vary in phenotypic expression and are usually inherited in an autosomal dominant manner. The teeth appear blue-gray or yellow-brown in color because the abnormally colored dentin shines through the translucent enamel. The teeth have increased susceptibility to fracture. Dentinogenesis Imperfecta Type I may be associated with Osteogenesis Imperfecta.
Abnormal tooth development can result from many other genetic and systemic conditions, but a comprehensive review is beyond the scope of this endeavor.

Enamel: Intensely hard calcareous substance that forms a thin layer partly covering the teeth; the hardest substance of the animal body; consists of minute prisms arranged at right angles to the surface and bound together by a cement substance.

Enamel hypoplasia has many potential etiologies.
Dentinogenesis and Amelogenesis Imperfecta are usually inherited in an autosomal dominant fashion.
Dentinogenesis Imperfecta Type I can be associated with Osteogenesis Imperfecta.

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