Alteration of enamel proteins in hypomaturation amelogenesis imperfecta.

Amelogenesis imperfecta (AI) is a diverse group of disorders that affects primarily the enamel of teeth through a number of developmental processes. The purpose of this study was to characterize the enamel proteins in normal enamel and in hypomaturation AI enamel. Impacted teeth, which were at similar stages of development, were obtained for analysis from an individual with AI and from normal healthy controls. Evaluation of the amino acid profile and quantity of organic material collected showed that there was an excess of enamel protein material that had an amelogenin-like amino acid profile in mature hypomaturation AI enamel. The AI enamel protein content was 5%, while the control enamel had 0.1% protein (by weight). These findings indicate that the maturation process had been altered in this type of AI, and that maturation did not progress beyond the initial stages of secondary mineralization. Since this disorder is inherited as an autosomal recessive condition, it seems likely that the primary defect involves an abnormality in the mechanism for protein removal in enamel maturation.