Journal of Dental Research, Vol 63, 629-634, Copyright © 1984 by International & American Associations for Dental Research Online Journals
Single bovine enamel particles examined by electron optics
W. J. Landis, M. Navarro, J. R. Neuringer and K. Kurz
Whole enamel scrapings from teeth of embryonic calves have been separated
by density gradient centrifugation in organic solvents into fractions (1.6
less than p less than 2.4 g/cm3) representing progressive stages of mineral
phase maturation. Single enamel particles or their small aggregates from
such fractions were examined by transmission electron microscopy, electron
diffraction, and high-spatial-resolution electron probe micro-analysis. The
electron optical methods demonstrated the presence of poorly crystalline
hydroxyapatite as the only detectable solid phase in all fractions.
Octacalcium phosphate and brushite were not identified in the fractions.
Changes in electron diffraction patterns were indicative of a progressive
increase in apatite crystallinity with enamel maturation. Molar Ca/P ratios
were found to range from 1.48 to 1.70, with a higher mean value obtained
for lower-density fractions (p less than 2.0 g/cm3). Lower-density
fractions contained some particles with high ratios (approximately equal to
2.0-4.0) and a non-uniform distribution of Ca and P, as revealed by
electron probe mapping. These characteristics are suggested as possibly
being related to carbonate phases in early enamel.
