Reduction in Dentin Permeability Using a Fluoride-Calcium-Phosphate Containing Solution

Dentin hypersensitivity can be reduced using treatments that obdurate dentin tubules. A stable solution containing a fluoride calcium phosphate (FCP) complex was reported to precipitate CaF₂ and calcium phosphate when the pH was raised. Objective: To determine the effect of sequential treatments with an alkaline solution followed by FCP on the hydraulic conductance (Lp) of etched dentin discs in vitro. Methods: The FCP solution contained 0.6M NaF, 2M CaCl₂, and 1.38M H₃PO₄. Dentin discs were etched by 6% citric acid for 30 s and rinsed thoroughly with distilled water. The treatment procedure consisted of (1) applying a 5N KOH solution by cotton swab for 1 min and dried by blowing air, and (2) applying the FCP solution by cotton swab for 3 min and similarly dried. The Lp of each dentin disc was measured, using a modified Pashley's flow system, before treatment (baseline), after the treatment, and after a 2-week incubation in a saliva-like solution (SLS) [1.2-mmol/L CaCl₂, 0.72-mmol/L KH₂PO_4, 30-mmol/L KCL and 50-mmol/L Hepes, pH=7.0]. At each time point, the Lp measurements were conducted before and after a 1-min brushing of the dentin disc. The change in Lp for each specimen is presented as relative Lp = (Lp / baseline Lp). Results: The mean baseline Lp was (1.1±0.6) µL cm^-2 sec^–1 H₂O cm^-1 (mean ± S.D.; n=9). After the treatment the mean relative Lp values were (0.008±0.003) and (0.296±0.103) before and after brushing, respectively. After the incubation, the mean relative Lp values were (0.034±0.015) and (0.045±0.011), respectively. Lp was reduced significantly (p<0.05) by the treatment. After the incubation in SLS, Lp did not change significantly with brushing (p>0.05). Conclusion: The experimental treatment was effective in reducing Lp of dentin discs.  Supported by NIDCR grant DE16416, ADAHF, and NIST.