Journal of Dental Research, Vol 69, 458-462, Copyright © 1990 by International & American Associations for Dental Research Online Journals
A comparison of the influence of lanthanum and fluoride on de- and remineralization of bovine enamel in vitro
K. Collys, D. Slop, L. de Langhe and D. Coomans
Vrije Universiteit Brussel, Faculteit Geneeskunde en Farmacie, PRTA, Belgium.
The influence of fluoride and lanthanum on enamel softening was compared by
hardness measurements and by determination of the calcium content in the
solution. The addition of lanthanum to an acetate buffer solution (0.05
mol/L, pH = 5.0) had no significant influence on the change of the
indentation length and on the calcium release, compared with those of the
control group. In the fluoride group, a moderate increase of the
indentation length and a reduced calcium loss were observed. In a second
experiment, surface-softened bovine enamel was treated with calcifying
solutions (Ca/P ratio = 1.67). Differences in treatment were created by the
addition of traces (2 ppm) of lanthanum, fluoride, or both. The acid
resistance of the treated enamel was evaluated by two successive softening
steps (0.1 mol/L acetate buffer, pH = 5.5). Alterations of the enamel
surface were longitudinally followed with a hardness tester. The addition
of fluoride, lanthanum, or both significantly improved the rehardening of
surface-softened enamel, compared with that of the control group. A 2 x 2
factorial analysis of variance showed that lanthanum and fluoride had a
highly significant main effect and a significant negative interaction
effect on the rehardening of surface-softened enamel. Subsequent acid
treatments revealed that only samples treated with a fluoride-containing
solution were adequately protected from further dissolution. The enamel
surfaces treated with a solution containing both lanthanum and fluoride
were covered with an acid-resistant surface coating. SEM observation of
this surface layer revealed the presence of globular and spherulite
structures.
