Single Fluoride Gel Application on Enamel under Severe Cariogenic Conditions

Methods: 37 subjects wore appliances situated in the lower jaw over two periods of 4 weeks. Bovine enamel slabs were mounted in the buccal aspect to these appliances. The specimens were covered with a titanium grid and were stored in a 20% sucrose solution two times a day for 30 minutes to allow for plaque growth and to simulate severe cariogenic conditions, respectively. On day one of each period, a 1.25% fluoride gel or a placebo gel was applied for 4 minutes using the tray application method. During the treatment periods, subjects wore the appliances for at least 20 hours per day, but not during eating and oral hygiene. The subjects cleaned their teeth with standard fluoride toothpaste (1400 ppm F^- from NaF) for the entire duration of the study. After the clinical phase, specimens were removed from the appliances and cleaned. Half of the specimens were sectioned perpendicular to the exposed surface for measurement of the mineral content and lesion depth using transverse microradiography. The remaining specimens were used to evaluate the fluoride content of the outermost 100 µm.

Results: In specimens treated with the fluoride gel almost no mineral loss or increase of lesions depth was measured compared to specimens that had been treated with the placebo gel (p<0.001). Regarding fluoride content no significant differences were found among the two groups.

Conclusions: A single application of a highly concentrated fluoride gel can prevent sound enamel from being demineralized even under severe cariogenic conditions.