The role of ‘CaF₂-like’ material in topical fluoridation of enamel in situ

Abstract

In this paper the role and importance of ‘CaF₂-like’ material deposited on enamel (F_on) by means of an APF gel and the varnishes Duraphat® and Fluor Protector® are described and discussed. The amount of F_on, determined by KOH extraction, is a measure of the amount of CaF₂-like material on the enamel surface. Fluoride in the enamel (F_in), determined by etching, is the amount of F⁻ bound in the solid enamel. F_on and F_in data are presented after various F⁻ treatments and after wearing enamel slabs in dentures for a period of 1 week. The results of this work show that if we compare the three fluoridating agents, APF gel, Duraphat varnish, and Fluor Protector varnish in situ, only Fluor Protector shows a measurable amount of F_on after 1 week. The amounts of F_on acquired by the enamel surface (one application) rank as APF gel ⌣ Duraphat ≫ Fluor Protector. Most likely, F_on in situ leaches away through the pellicle, with an apparent diffusion coefficient of about 10-⁶ cm² sec⁻¹. The F_in data show that after APF gel or Duraphat treatment a substantial amount of F_in leaches away during 1 week in situ; the F_in values of Fluor Protector do not change. The efficiency of the fluoridating agents is most likely determined by the application period and fluoride availability. For APF gel, Duraphat, and Fluor Protector about 5%, 1%, and 44% of the available fluoride participates in the fluoridation process. CaF₂-like globules are known to precipitate after gel or varnish treatment on the enamel surfaces and can be dissolved in KOH solution. The chemical analysis of these KOH solutions shows that the molar Ca/F ratio is about 0.5. The accuracy of the experiment is, however, insufficient to conclude whether the globules are pure CaF₂.

Key Words:

• Enamel etching
• fluoride gel
• fluoride varnish
• preventive dentistry