Amelogenesis imperfecta

Abstract

Amelogenesis imperfecta (AI) represents a group of developmental conditions, genomic in origin, which affect the structure and clinical appearance of enamel of all or nearly all the teeth in a more or less equal manner, and which may be associated with morphologic or biochemical changes elsewhere in the body. The prevalence varies from 1:700 to 1:14,000, according to the populations studied. The enamel may be hypoplastic, hypomineralised or both and teeth affected may be discoloured, sensitive or prone to disintegration. AI exists in isolation or associated with other abnormalities in syndromes. It may show autosomal dominant, autosomal recessive, sex-linked and sporadic inheritance patterns. In families with an X-linked form it has been shown that the disorder may result from mutations in the amelogenin gene, AMELX. The enamelin gene, ENAM, is implicated in the pathogenesis of the dominant forms of AI. Autosomal recessive AI has been reported in families with known consanguinity. Diagnosis is based on the family history, pedigree plotting and meticulous clinical observation. Genetic diagnosis is presently only a research tool. The condition presents problems of socialisation, function and discomfort but may be managed by early vigorous intervention, both preventively and restoratively, with treatment continued throughout childhood and into adult life. In infancy, the primary dentition may be protected by the use of preformed metal crowns on posterior teeth. The longer-term care involves either crowns or, more frequently these days, adhesive, plastic restorations.

Figure 1

Phenotypic descriptions of amelogenesis imperfecta. Amelogenesis imperfecta may be subdivided at the clinical level into various forms depending on the type of defect and stages of enamel formation disturbed: hypoplastic (a, b, c, d), dysmineralised (e, f), hypomature (g, h). Note the pitted and ridged appearance of the enamel in a, the association of pitted enamel and open bite in b. c and d are slightly different phenotypic manifestations in a sister (showing a horizontal banding pattern) and brother. In the hypomineralised form (e and f) the enamel is rough, soft and discoloured. Amelogenesis imperfecta may be part of a syndrome as in f), a case of amelogenesis imperfecta and cone rod dystrophy. Various enamel defects (both hypoplastic and hypomineralised) may coexist in the same patient or even the same tooth (f). The hypomaturation forms (g, h) display an enamel of normal thickness and hardness but with a white-ish surface. They may be mistaken for fluorosis. (from A. Bloch-Zupan).