Advances in Dental Research, Vol 3, 241-248, Copyright © 1989 by International & American Associations for Dental Research
Crystal morphology and decalcification patterns compared in rat and human enamel and synthetic hydroxyapatite
J. W. Simmelink and S. C. Abrigo
The purpose of this investigation was to compare morphology and dissolution
patterns by ultrastructural examination of rat and human enamel crystals as
well as synthetic apatite crystals. Mature enamel crystals were of
particular interest, since crystal maturation appears to be inhibited in
amelogenesis imperfecta. Specimens were isolated from developing and mature
rat incisor enamel. Rat enamel, mature human enamel, and synthetic apatite
were thin-sectioned without decalcification and examined by transmission
electron microscopy. Some sections were exposed to acid, and selected
synthetic apatite sections were further treated for removal of embedding
plastic, followed by vacuum-shadow-coating with carbon. Results showed that
cross-sections of rat, human, and synthetic crystals had a distortion in
the flattened hexagonal outline in regions where the growth of one crystal
impinged on another. Crystal dissolution occurred preferentially along the
c-axis, producing a central defect or hole in the crystals. Preliminary
studies with weak acid on mature human enamel indicate that the relatively
soluble crystal core is quickly dissolved, while the outer shell remains
intact over a much longer period of time. In the mature rat and human
enamel, this crystal hole formation had a consistent dimension of
approximately 10-nm thickness. The crystal hole dimension was the same size
as crystals that are formed during the early secretory phase in rat
amelogenesis. Acid-treated synthetic apatite also showed dissolution of the
crystal core along the c-axis, but dimensions of the hole were not
consistent.(ABSTRACT TRUNCATED AT 250 WORDS)
