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Dentinogenesis imperfecta (hereditary Opalescent Dentin) is a genetic disorder of tooth development. This condition causes teeth to be discolored (most often a blue-gray or yellow-brown color) and translucent. Teeth are also weaker than normal, making them prone to rapid wear, breakage, and loss. These problems can affect both primary (baby) teeth and permanent teeth. This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. Dentinogenesis imperfecta affects an estimated 1 in 6,000 to 8,000 people.

[edit] Types

Researchers have described three types of dentinogenesis imperfecta with similar dental abnormalities.

Type I: Occurs in people who have osteogenesis imperfecta, a genetic condition in which bones are brittle and easily broken.It is usually an autosomal dominant trait with variable expressivity but can be recessive if the associated osteogenesis imperfecta is of recessive type. This type is no longer considered true dentinogenesis imperfecta as the mutations occur in different genes in the two conditions, though the clinical and radiological features are the same.

Type II : Occurs in people without other inherited disorders ie Osteogenesis imperfecta.It is an autosomal dominant trait. A few families with type II have progressive hearing loss in addition to dental abnormalities.

Type III dentinogenesis imperfecta was first identified in a population from Brandywine, Maryland. Researchers now believe that type II and type III may be the same disorder.

Mutations in the DSPP gene have been identified in people with type II and type III dentinogenesis imperfecta. Type I occurs as part of osteogenesis imperfecta, which is caused by mutations in Collagen(COL1A1 and COL1A2) genes. The DSPP gene provides instructions for making three proteins that are essential for normal tooth development. These proteins are involved in the formation of dentin, which is a bone-like substance that makes up the protective middle layer of each tooth. Mutations in the DSPP gene may affect the proteins made by the gene, leading to the production of abnormally soft dentin. Teeth with defective dentin are discolored, weak, and more likely to decay and break. It remains unclear how DSPP mutations lead to hearing loss in some families with dentinogenesis type II.

[edit] Clinical features

Clinical appearance is variable.However, the teeth usually involved and more severely affected are deciduous teeth in type 1; whereas in type 2 both the dentitions are equally affected.

The teeth may be gray to yellowish brown. They exhibit transluscent or opalescent hue.Enamel is usually lost early due to loss of scalloping at DEJ. The teeth however are not more susceptible to dental caries than normal ones.

[edit] Radiographic features

Type 1 and 2 show total obliteration of the pulp chamber.

Type 3 shows thin dentin and extremely enormous pulp chamber.These teeth are usually known as Shell Teeth.

[edit] Histology

Dentinal tubules are irregular and are bigger in diameter. Areas of uncalcified matrix are seen. Sometimes odontoblasts are seen in dentin.

This article incorporates public domain text from The U.S. National Library of Medicine