Fluoride Uptake by Enamel Surfaces, Root Surfaces and Cavity Walls following Application of a Fluoride Varnish in vitro

Twelve root surfaces and enamel surfaces adjacent to fresh amalgam restorations were treated with the fluoride varnish Fluor Protector® for 48 h in vitro. The untreated half of each buccal surface served as a control. The varnish was removed after 48 h and the teeth immersed in artificial saliva for 20 h. Electron probe microanalysis revealed that in 75% of the recordings the fluoride concentration in the treated enamel surfaces ranged from 1,500 to 4,500 ppm, while the remaining 25% showed concentrations below the detection limit (1,500 ppm). All the treated root surfaces showed concentrations greater than 1,500 ppm; values up to 25,000 ppm were recorded. In the enamel and dentin cavity walls, fluoride concentrations above the detection limit were recorded in 5 and 55% of the cases, respectively. In the dentin walls, values up to 7,000 ppm were found. In the untreated enamel surfaces, root surfaces and cavity walls, the fluoride concentration was generally below the detection limit. This study demonstrated a considerable uptake of fluoride from the varnish by enamel and root surfaces. In addition, the cavity walls had taken up fluoride ions released from varnish applied on the tooth surface adjacent to amalgam fillings.