The effect of fluoride varnishes on caries lesions: an in vitro investigation

The purpose of this study was to investigate the effect of five commercially available fluoride varnishes (FV) on caries lesions. Ninety bovine enamel specimens were assigned to five varnish groups (n = 18). Early caries lesions were created in the specimens and characterized using Vickers surface microhardness number (VHN). FV was applied to each group of specimens. Immediately afterwards, 7.5 ml of artificial saliva (AS) were pipetted over each group of specimens, collected and renewed every 15 min for 6 h. AS samples were analyzed for fluoride using an ion-specific electrode. Enamel fluoride uptake (EFU) was determined using the acid etch technique. Each group was then subjected to a pH cycling regimen for 5 days after which VHN was determined again. One-way analysis of variance (ANOVA) was used for data analysis. FVs differed in their rehardening capability (highest mean value was for Enamel Pro = 32.3 +/- 5.8 and lowest mean value was for Vanish = 18.9 +/- 11.3). No significant difference in EFU was found among groups. Total fluoride release over 6 h was in the order of MI Varnish (303 mu g/ml) > Enamel Pro (217 mu g/ml) > Flor-Opal (153 mu g/ml) > PreviDent(84 mu g/ml) > Vanish(28 mu g/ml). Delta VHN and fluoride release characteristics differ among FV products. These differences may be attributed to the different compositions and physical properties of the tested FV. Fundamental, comparable research on FV and how different formulations affect early caries lesion rehardening, fluoride release into saliva, and uptake by teeth is scarce.