Enamel microhardness and histological features of composite enamel pearls of different size.

The aim of this study was to investigate the enamel microhardness and the histological features of eight enamel pearls of various size. The microhardness of the pearl enamel ranged from 272.4 to 407.2 Vickers microhardness values (VMV) and resembled that of the enamel of the carrier teeth (277.1-424.3). A histological resemblance between the tissues of the enamel pearls and those of the carrier teeth was also found. The resemblance was more pronounced in larger pearls, which showed a variability of the enamel microhardness and structure in the occlusal-cervical direction typical of the tooth crown. Large pearls also exhibited a root and a pulp. Some histological features of the enamel pearls were probably caused by pressures exerted on the developing pearl by its surroundings. It is suggested that the histogenesis of small and large pearls is based on the ability of the developing root of the carrier tooth to behave in part as a new tooth germ.