Topical fluoride application and lesion progression in vitro

The objectives of this investigation were to study the effects of topical fluoride application on white spot enamel and the effect that this application would have on a second acid exposure (lesion progression). Artificial white spot lesions of approximately 200 micron were created with an acidified gel technique, central control sections were removed, and the remaining tooth halves were randomly paired, with one half serving as an untreated control while the other received a single four-minute application of 1.23% (w/v) fluoride solution of either NH4F, Na2SnF6, APF, or TiF4. Both tooth halves were sectioned following progression and examined with polarized light microscopy. Lesion depth, internal pore volume, and presence, size and shape of dark zones were determined. The considerable variation among progressed lesions revealed no significant benefit from any topical fluoride treatment.