Fluoride varnish concentration gradient and its effect on enamel demineralization

PURPOSE: Two of the 4 fluoride varnishes available on the American market today are sold in 10-mL tubes of 5% NaF varnish (Duraphat and Duraflor). Pilot studies have shown that a separation of contents within these tubes exists. The purpose of the current study was 4-fold: (1) to measure the fluoride concentration gradient in 10-mL tubes of fluoride varnish, based on resting position of the tube prior to use; (2) to compare and contrast fluoride concentration gradients of Duraphat, Duraflor, and CavityShield; (3) to compare this gradient to the ability to inhibit caries in an artificial caries environment; and finally, (4) to determine if quantitative light fluorescence (QLF) can detect differences in lesions developed when exposed to an artificial caries environment and fluoride varnish. METHODS: Human teeth specimens were subjected to a caries challenge and treated with a sample of fluoride varnish from 1 of 5 categories: Duraphat stored horizontally and vertically for 1 week, Duraflor stored horizontally and vertically for 1 week, or a CavityShield 0.4 mL "unidose." All specimens were then analyzed with the QLF system and with confocal microscopy. RESULTS: Results showed no significant fluoride ppm differences exist between groups (P=.29). It was shown that the order in which Duraflor varnish was dispensed from tubes significantly affected the fluoride concentration (P<.05). The order effect was not significant for Duraphat (P=.99). QLF data analysis showed there was no significant difference (P>.05) in the amount of remineralization obtained by using any varnish stored in any position. CONCLUSIONS: These results indicate that all 3 brands of fluoride varnish are able to remineralize incipient in vitro carious lesions, regardless of what part of the 10-mL tube the varnish is taken from. However, a fluoride concentration gradient exists in tubes of Duraflor. Also, QLF is able to detect demineralized and remineralized incipient lesions.