Fluoride in an experimental cavity varnish

The aim of the present study was to assess the behavior of fluoride in an experimental cavity varnish. The varnish consisted manily of ethanol and the fluoride was added as a 1 M solution of sodium fluoride. When increasing amounts of ethanol were added to fluoride in water the readings (mV) given by a fluoride ion electrode unexpectedly increased. This effect of ethanol on the readings was less marked at the highest fluoride concentrations. At considerable excess of ethanol, as in the varnish, reproducible readings were obtained. Free fluoride ions corresponding to an effective concentrations of 1 M aqueous fluoride seemed to be present in the varnish. When various amounts of hydroxyapatite were added to the varnish, the fluoride content of the varnish was reduced whereas an increased amount of fluoride was recovered from the apatite.