Journal of Dental Research, Vol 65, 698-702, Copyright © 1986 by International & American Associations for Dental Research Online Journals
In vivo effects of a SnF2 gel on acid-softened enamel
J. W. Clark, A. Quiros, R. E. Corpron, F. G. More and C. J. Kowalski
The purpose of this investigation was to study the intra-oral rehardening
of acid-softened enamel and fluoride uptake from SnF2 gel. Bovine enamel
slabs were softened with 0.1 mol/L lactate buffer at pH 4.0 for 14 hrs and
then mounted in a mandibular removable Hawley appliance. Control slabs were
worn for 96 hrs by seven adult males whose teeth were brushed daily with a
fluoride-free dentifrice. Test slabs were exposed once/day to 0.4% SnF2
gel. The gel was swabbed onto the slabs for one minute before being
replaced in the mouth unrinsed. The natural dentition was brushed 4 X /day
with a fluoride-free dentifrice. Microhardness testing was performed after
intra-oral exposure (IOE) and after acid-resistance-testing (ART) following
immersion in 0.01 mol/L lactate buffer for 24 hrs at pH of 4.0. Fluoride
uptake was measured on separate controls, test slabs, and test slabs after
ART, with 0.5 mol/L HClO4 etches of from 15 to 60 sec. The F content was
measured with a F-ion-specific electrode and the phosphate content by
spectrophotometry. Following IOE, microhardness recovery was 35.6% for
control and 37.9% for test slabs, and control slabs retained 1.4%
resistance to acid, as compared with 18.6% for the test slabs. The F
content of control slabs was significantly less than that of SnF2-treated
slabs from 5 to 60 micron in depth, and the F content of SnF2-treated slabs
after ART was significantly less at depths of from 5 to 35 micron than that
of SnF2-treated slabs not exposed to ART. Both control and SnF2 enamel
slabs demonstrated rehardening after IOE, but only SnF2-treated enamel
retained a significant fraction of that rehardening after ART.
