Fluoride uptake on dry versus water-saliva wetted human enamel surfaces in vitro after topical application of a varnish (Duraphat) containing fluoride.

The uptake of fluoride was studied in vitro after application of Duraphat varnish on dry versus wetted enamel surfaces. 30 sound premolar teeth extracted for orthodontic reasons were randomly divided into three experimental groups. Duraphat varnish was topically applied for 6 hours to the air dried surfaces of ten teeth (group 1). In group 2, 10 teeth were also treated with Duraphat but the enamel surfaces were water-wetted. In group 3, surfaces were wetted with fresh chewing-stimulated human saliva. The varnish was allowed to remain on the surfaces for 6 hours in all groups whereafter all teeth stored in synthetic saliva (37 degrees C) for one week before F-analysis performed by the acid etching method. The results indicate that the F-uptake from Duraphat varnish is increased significantly by its application to dry surfaces compared to wetted surfaces. This observation may be of clinical importance and should be further investigated.