Fluoride uptake in plaque-covered enamel after treatment with the fluoride lacquer Duraphat.

The amount of alkali-soluble and alkali-insoluble fluoride was determined in human enamel after one- and six-hour treatments with Duraphat. The application was carried out on: (1) slightly demineralized enamel covered with artificial plaque, (2) cleaned, slightly demineralized enamel, and (3) sound enamel without pre-treatment. After a single Duraphat treatment lasting six hours, fluoride uptake was higher than after Duraphat treatment for just one hour in all experimental groups. More fluoride was acquired in both slightly demineralized, plaque-covered and slightly demineralized, cleaned enamel than in sound enamel. Plaque significantly hampered the formation of alkali-soluble fluoride precipitation on demineralized enamel, but its influence on the amount of fluoride taken up by the enamel was minor.