Fluoride treatment and microhardness of dentin.

Effects of various fluoride treatments on the microhardness of human dentin were determined. Treatment with acidulated phosphate-fluoride at pH 3.0 induced a significant (p less than .05) softening when compared to treatment with water. APF at pH 4.0 did not bring about a significant change. Response to treatment with 0.4% SnF2 did not differ significantly from water treatment. Sequential treatment with APF (pH 4.0) followed by SnF2 produced significant (p less than .05) hardening of dentin. This hardening with APF-SnF2 differed at a high level of significance (p less than .001) from the softening produced by the pH 3.0 APF. A similarly significant difference was found between this single APF treatment and the single SnF2 treatment. When hardening of exposed dentin surfaces is desired, the sequential treatment method should be employed.