Insoluble NaF in Duraphat® may prolong fluoride reactivity of varnish retained on dental surfaces.

There is no consensus about the clinical recommendation of the time that Duraphat® varnish should be maintained on enamel surfaces without suffering mechanical disturbance by the patient. Considering the importance of calcium fluoride (CaF2)-like reservoirs on the anticaries effect of professional fluoride application, an in vitro study was designed to test the reactivity of Duraphat® varnish with enamel forming these reservoirs as a function of time. Since most fluoride in Duraphat® varnish is insoluble to react and form products on enamel, the relative contribution of the varnish soluble and insoluble fluoride fractions to the reactivity was also evaluated.