In vitro evaluation of fluoride varnish on overdenture abutments.

Statement Of Problem: No clinical study has evaluated the efficacy of fluoride varnish as a topical fluoride agent for the protection of overdenture abutments from dental caries.

Purpose: This study assessed the efficacy of a fluoride varnish in protecting overdenture abutments from demineralization in an in vitro environment.

Material And Methods: Eighty caries-free, extracted teeth were sectioned and domed immediately below the cementoenamel junction, simulating overdenture abutment preparations. Acid resistant nail varnish was painted on all surfaces except for a window (1 x 4 mm) on the prepared occlusal dentin surfaces. Teeth were randomly divided into 4 groups of 20 specimens: control, washed with deionized/distilled water; Daily Gel, treated with Karigel-N (5,000 ppm) for 4 minutes daily; Weekly Gel, treated with Karigel-N for 4 minutes weekly; and Weekly Varnish, treated with Duraflor (22,600 ppm) weekly. The varnish was removed using a blade 24 hours after each application to simulate the clinical loss of the varnish. Teeth were then placed in a cycle of demineralization (2.2 mMol/L CaCl(2)2H(2)O, 2.2 mMol/L KH(2)PO(4), and 50 mMol/L acetic acid at pH 4.3) for 6 hours and remineralization (1.5 mMol/L CaCl(2)2H(2)O, 0.9 mMol/L KH(2)PO(4), and 150 mMol/L KCl at pH 7.0 for 17 hours) for 21 days. Half the teeth in each group were brushed with no dentifrice for 10 seconds, twice daily. Teeth were sectioned at 100 +/- 10 microm buccolingually and evaluated under polarized light microscopy and contact microradiography. The depth of each lesion and the width of the remineralization bands were measured (mm). Analysis of variance models and T-tests were used to assess the effects of different treatments (alpha=.05). Duncan multiple range tests were then chosen as post hoc tests to evaluate the statistical significance of all pairwise comparisons.

Results: The control group had the deepest lesions (mean depth 400 +/- 39 microm). The lesions from the varnish and daily gel groups were significantly shallower than the lesions in both the control group and the weekly gel group. The remineralization bands in the varnish group were 52% wider than the control group bands. However, the daily gel group had the largest increase in band width (117% increase) compared with the control group. There were significant differences between all groups for net depth (lesion depth minus the remineralization band) (P<.0001). Daily application of fluoride gel was significantly more effective than the other treatments tested. Brushing was not a significant factor.

Conclusion: Within the limitations of this in vitro study, treatment of overdenture abutment with various topical fluorides significantly inhibited demineralization and enhanced remineralization of cut occlusal dentin surfaces. Daily use of Karigel-N was the most effective treatment, followed by the weekly application of Duraflor varnish.