An In Vitro Investigation of Anticaries Efficacy of Fluoride Varnishes

Most currently marketed fluoride varnishes (FVs) have not been evaluated for their effectiveness in preventing dental caries. The objective of this study was to investigate the anticaries efficacy, measured as fluoride release into artificial saliva (AS); change in surface microhardness of early enamel caries lesions; and enamel fluoride uptake (EFU) of 14 commercially available FVs and two control groups. Bovine enamel specimens (5×5 mm) were prepared and assigned to 18 groups (n=12). Early caries lesions were created in the specimens and characterized using Vickers microhardness (VHN lesion ). FV was applied to each group of specimens. Immediately afterward, specimens were incubated in 4 mL of AS for 18 hours, which were collected and renewed every hour for the first six hours. AS samples were analyzed for fluoride using an ion-specific electrode. Specimens were then brushed for 20 seconds with toothpaste slurry and subjected to pH cycling consisting of a four-hour/day acid challenge and one-minute treatments with 1100 ppm F dentifrice for five days. Microhardness was measured following pH cycling (VHN pos ). EFU was determined using microbiopsy. Acid resistance (eight-hour demin challenge) was performed after pH cycling, and microhardness was measured (VHN ar ) and compared with baseline values to test the FV impact after pH cycling. One-way analysis of variance was used for data analysis ( α =0.05). FVs differed in their release characteristics (mean ± SD ranged from 14.97 ± 2.38 μg/mL to 0.50 ± 0.15 μg/mL), rehardening capability (mean ± SD ranged from 24.3 ± 15.1 to 11.7 ± 12.7), and ability to deliver fluoride to demineralized lesions (mean ± SD ranged from 3303 ± 789 μg/cm 3 o 707 ± 238 μg/cm 3 ). Statistically significant but weak linear associations were found between ΔVHN (post - lesion) , EFU, and fluoride release (correlations 0.21-0.36). The results of this study demonstrated that differences in FV composition can affect their efficacy in in vitro conditions.