The polarized light microscopy and ultrastructure of Polynesian pigmented tooth enamel

Transmitted and polarized light microscopy of unerupted and erupted teeth affected by a pigmented anomaly found in two geographically isolated Polynesian populations, the New Zealand Maori and the French Polynesian Marquesas Islander, showed similar histological characteristics. Mounted in water, the pigmented areas were positively birefringent and covered with a thin negatively birefringent surface layer 200–250 μm thick. Cervical areas were negatively birefringent. Transmission electron microscopy of argon-ion-beam thinned specimens of affected enamel revealed large voids, disruption in the packing of crystals and spacing at prism boundaries. In the surface layer of enamel from erupted and unerupted teeth, the intra- and interprismatic spaces were occluded by fine crystals or amorphous material. A well-defined prism structure and close crystal packing were found in cervical enamel. The ultrastructure of these pigmented enamels was similar to and consistent with a hypomaturation type of amelogenesis imperfecta.