Method: 56 human coronal dentin disks (1±0.2mm) were placed in a modified split-chamber device adapted in Flodec. The maximum hydraulic conductance values were taken after phosphoric acid etching (15s). The dentin disks were randomly allocated in 7 groups (n=8) according to the treatments. Thereafter, the minimum (occlusal smear layer) and the maximum (after acid-etching) hydraulic conductance values were recorded. The treatments were performed for 4 minutes as following: NaF varnish/solution (2.45%F, pH 5.0), TiF4 varnish/solution (2.45%F, pH 1.2), free fluoride varnish (pH 5.0), no treatment (negative control), and potassium oxalate gel (Sensiactive-positive control). After the removal of the products, the hydraulic conductance was assessed. The samples were then exposed to a brief acid challenge (6% citric acid, pH 2.1, 1min) and the final hydraulic conductance was recorded. Two samples per group were analyzed using SEM. The data were statistically analyzed (p<0.05).
Result: After treatment, the samples from Sensiactive and NaF varnish groups presented lower hydraulic conductance compared to the negative control. Sensiactive also significantly differed from placebo varnish (Kruskall-Wallis/Dunn, p<0.0001). After the acid challenge, all treatments were effective in reducing the dentin permeability compared to the negative control. However, only Sensiactive significantly differed from placebo varnish (ANOVA/Tukey, p<0.0001). The SEM showed that Sensiactive was effective in obliterating the dentin tubules even after the acid challenge, while the treatments with fluoride caused only partial dentin obliteration.
Conclusion: It can be concluded that the TiF4 varnish and solution were less effective than the NaF varnish and Sensiactive immediately after treatment; however, all tested products were similar in reducing dentin hydraulic conductance/permeability after acid challenge.