Fluoride Acquisition on and in Fluorotic Human Enamel After Topical Application in Vitro

The uptake of alkali soluble and alkali insoluble fluoride on and in fluorotic enamel was investigated in vitro. Teeth from Kenya, assigned score 3 in accordance with Thylstrup-Fejerskov's fluorosis index, were used. The enamel was treated with either a neutral 2% NaF solution, a 0.2% NaF solution (pH 5.5), or the supernatant from a 0.1% NaF-containing toothpaste (pH 7). The treatment time was 1 h. The reaction product formed on the enamel was analyzed by KOH extraction and acid etching. Significantly higher amounts of alkali soluble fluoride were formed on the enamel from the 2% and 0.2% NaF solutions, as compared with the control. There was also a significant increase in the firmly bound fluoride after treatment with the neutral 2% NaF solution.