Journal of Dental Research, Vol 68, 1289-1292, Copyright © 1989 by International & American Associations for Dental Research Online Journals
Fluoride incorporation into and retention in remineralized enamel
Y. Iijima and T. Koulourides
Department of Preventive Dentistry, Nagasaki University School of Dentistry, Japan.
This study assessed the incorporation of fluoride into remineralized enamel
and the stability of the incorporated fluoride under various test
conditions. Lesions were produced on bovine enamel slabs by a two-day
immersion in 0.01 mol/L lactic acid buffer containing 3.0 mmol/L Ca, 1.8
mmol/L P, and 1% CMC adjusted to pH 4.0 at 37 degrees C. The
remineralizaing solution contained the same amount of Ca, P, and CMC, plus
150 mmol/L NaCl and 3 ppm F, and was adjusted to pH 7.0 at 37 degrees C.
All slabs were exposed to this unstirred solution, which was changed every
two days during the ten-day remineralizing period. The remineralized slabs
were divided into four groups. Group A (the control group) received no
further treatment. The other three groups were exposed for 24 h to either
the intra-oral environment (Group B), a 1.0 mol/L KOH solution (Group C),
or a 0.01 mol/L lactic acid buffer (Group D). Fluoride incorporation
assessed by abrasion biopsy in 10-microns layers showed about 10,000 ppm F
maximum in Group A. Similar levels of fluoride concentration from the
surface to approximately 30 microns thick were found in Groups A, B, and C.
No appreciable fluoride was released from remineralized slabs from Groups B
or C, and only a small fraction from Group D. Statistical analyses of the
fluoride values showed no significant differences between the various test
conditions in any of the layers sampled. No difference was evident in the
Ca/P ratio between the ten-day remineralized enamel (Group A) and the
treatment groups. The lack of appreciable fluoride loss from enamel with
any of the above three conditions indicated a stable fixation of fluoride
in the remineralized enamel lesions.
