Fluoride Ion Release Characteristics of Fluoride-Containing Varnishes-An In Vitro Study

Despite the latest advances in orthodontic treatment, white spot lesions remain a common side effect of fixed appliance therapy. An effective treatment for the prevention of white spot lesions is the use of fluoride-containing products. The aim of the present in vitro study was to check the durability of the tested products for their fluoride release into the surrounding solution. Three varnishes (Protecto CaF2 Nano one-step seal, Bifluorid 12 single dose, and Fluor Protector S) were applied to hydroxyapatite discs and kept in diluted Total Ionic Strength Adjustment Buffer III (TISAB III) solution for fluoride ion release measurement. A group of clear hydroxyapatite discs served as the control group. The carrier discs (N = 40) underwent three thermal cycling runs for 20 days. Before the first run and after each run, the fluoride ion concentration in the solution was measured at appointed times (T) T0, T1, T2, and T3. Fluoride ion release was highest at T1 for all products (median values for Protecto CaF2 Nano one-step seal: 0.09 ppm, Bifluorid 12 single dose: 37.67 ppm, and Fluor Protector S: 3.36 ppm) except for the control group, showing its peak at T0 (0.04 ppm). There was a significant difference between the tested fluoride varnishes at all measurement times. Bifluorid 12 achieved significantly higher fluoride release values than the other products (p < 0.05 at all measurement times). A solitary product application of only once or twice per year, as stated by the manufacturers, cannot be supported.