Ultrastructural study of tooth enamel with amelogenesis imperfecta in AI-nephrocalcinosis syndrome

This paper describes the ultrastructure of the affected enamel and the clinical features in two siblings with the syndrome of nephrocalcinosis and amelogenesis imperfecta. Nephrocalcinosis was diagnosed by intravenous pyelography, and confirmed by ultrasonography and CT scan. Amelogenesis imperfecta AI was diagnosed clinically and histologically. Light microscopy showed that the affected enamel surfaces were rough and the enamel was hypoplastic and mainly positively birefringent. Scanning electron microscopy revealed a rough and extensively cracked enamel surface covered with oval shaped blister-like protrusions. TEM showed porous enamel consisting of loosely packed and randomly oriented thin ribbon-like crystals with little or no prismatic structure. Observations showed that hypoplasia together with hypocalcification and/or hypomaturation defects were present in the same tooth, indicating the possibility of an abnormality in interstitial matrix, leading to dystrophic calcification in the kidney and abnormal tooth enamel formation, or alternatively an involvement of two separate but closely linked genes.