Comparison of Enamel Fluoride Uptake from Five Fluoride-Containing Topical Treatment Products

Purpose: To observe and compare enamel fluoride uptake in enamel by three fluoride varnishes, a fluoride foam, and a fluoride gel.

Methods: Bovine incisors were ground and cut into six groups (n=10) of cubic samples, set in resin cement such that a single square surface of facial enamel was exposed in each sample. These enamel surfaces were polished and treated, with a group assigned to each of three 5% sodium fluoride varnishes (BISCO, 3M ESPE, GC America), a fluoride foam (Dentsply Sirona), a fluoride gel (Crosstex International, Inc), as well as a water control group. After application of product, the samples were agitated at 37°C before removal of product by potassium hydroxide solution (10mL, 1.0M, saturated with calcium phosphate). A layer of exposed enamel was dissolved in each sample with perchloric acid (2.5mL, 1.0M) which was then neutralized with sodium hydroxide. The resulting solution was buffered in TISAB II and measured for fluoride content by ion selective electrode (ISE), which was adjusted for sample surface area.

Results: Enamel Fluoride Uptake (EFU) was observed from each group with the following mean values and standard error: 8.32±0.44 μg/cm2, 6.11±0.62 μg/cm2, and 4.04±0.20 μg/cm2 in the BISCO, 3M ESPE, and GC America varnishes, 6.52±0.64 μg/cm2 in the fluoride foam, 7.03 ± 0.51 μg/ cm2 in the fluoride gel, and 1.59 ± 0.11 μg/cm2 in the control group.

When in contact with tooth enamel, topical fluoride treatments including varnishes, gels and foams can induce fluorapatite by chemically incorporating fluoride in the tooth structure. This enamel fluoride uptake can be measured and compared to guide clinicians on the relative efficacy of different fluoride treatments. Results demonstrated here show that the BISCO varnish has a statistically higher EFU compared to other tested products.