Journal of Dental Research, Vol 62, 964-968, Copyright © 1983 by International & American Associations for Dental Research Online Journals
Concentration changes in surface Ca, P, F, Zn, Fe, and Sr during white spot formation
A. W. Crawford and H. J. de Bruin
The purpose of this study was to investigate the mechanism of surface layer
formation in artificial white spots. Two nondestructive nuclear
micro-analysis techniques were employed to analyze windows of human dental
enamel at progressive stages of an artificial lesion. Fluoride
concentrations were measured to a depth of 9 micron using resonant reaction
profiling. Surface concentrations of Ca, P, Zn, Fe, and Sr were measured
using proton-induced X-ray emission. The enamel windows were analyzed
longitudinally after zero, four, and 16 hours' exposure to lactic acid gels
of pH 3.7 and pH 4.5. During the first four hr of lesion formation,
nonfluoridated apatite was preferentially removed from the surface with up
to a 40% loss of Ca and P, depending on the gel pH. The next 12 hr saw a
build-up of Ca and P in the surface to values approaching those of healthy
enamel. In comparison, F and Sr concentrations changed very little, Fe
tended to show a small increase at the end of each demineralization period,
and Zn was less readily lost and gained than was Ca. These results and
others suggest that the white spot surface layer phenomenon is a combined
demineralization/remineralization process aided by, but not requiring, the
presence of endogenous fluoride.
