A mineralized cuticular structure with connective tissue characteristics on the crowns of human unerupted teeth in amelogenesis imperfecta: A light and electron microscopic study

Abstract

Premature degeneration and absence of the reduced enamel epithelium was observed in two unerupted teeth from a patient with amelogenesis imperfecta. This epithelial degeneration was accompanied by the patchy formation of a mineralized cuticular structure resembling cementum on the follicular surface facing the enamel. The demineralized cuticle showed histochemical evidence of a high content of collagen and acid mucopolysaccharide. Electron microscopic studies failed to reveal the presence in the cuticle of typically banded collagen fibrils. The cuticle was granular and showed a laminated internal structure. Although the cuticle may represent a form of afibrillar cementum, it should be noted that its formation appeared unrelated to direct cellular synthesis. Rather, it appeared to be associated with the degenerative process affecting the reduced enamel epithelium. The possibility that cuticle formation is dependent on adsorption by the enamel of connective tissue components was suggested. The degeneration of the reduced enamel epithelium would merely allow these connective tissue components to gain access to the enamel surface. The resemblance of the coronal cuticle in amelogenesis imperfecta to that found near the cemento-enamel junction of normal human teeth was pointed out, both with respect to ultrastructure and possible origin. It may be that these cuticular structures should be considered under the category of acquired pellicles with the understanding that their formation occurs in unerupted teeth, in areas of the crown not covered by an intact layer of reduced enamel epithelium.