High-resolution study by transmission electron microscopy of a microhypoplasia of the human enamel surface

The lesion of microhypoplasia of an unerupted tooth was composed of small, irregularly distributed crystals, similar to those of immature and hypomineralized enamel. The lesion appeared to be a defect of crystal growth and maturation, probably involving a partial and momentary failure of the operating cycle of an ameloblast.