Advances in Dental Research, Vol 3, 203-210, Copyright © 1989 by International & American Associations for Dental Research
Ultrastructure and composition of enamel in human dental fluorosis
T. Yanagisawa, S. Takuma and O. Fejerskov
Materials used in this work were 13 permanent molars exhibiting dental
fluorosis (between 5 and 9 on the Thylstrup-Fejerskov scale, 1978) obtained
from adults (aged 20-40 years) living in regions with 3.5 ppm fluoride in
the water supplies. Small but deep occlusal caries lesions necessitated
extraction. Light and polarized microscopic, microradiographic, electron
microscopic, and electron-probe- and ion-micro-analytical studies were
made. Enamel surfaces were generally cloudy to opaque, with several pits or
defects of various sizes and degrees of brown-staining. An extensively
hypomineralized area extended from the inner enamel to the surface layer,
which was mineralized to a high degree. The hypomineralized area contained
sparsely arranged, flattened, hexagonal crystals with either perforated
centers or defects extending from the perimeter and indicating either no or
low fluoride content. The highly mineralized surface layer, however, was
composed of many large, flattened, hexagonal crystals and extremely small,
irregularly shaped crystals. Both types were free of central perforations
and defects. A high fluoride concentration was determined in the highly
mineralized surface layer. These findings suggest that the hypomineralized
area undergoes caries-like changes in terms of crystal dissolution and that
the highly mineralized surface layer contains hydroxyapatite and
fluoridated-hydroxyapatite, or fluorapatite, or both.
