Fluoride release from fluoride varnish under in vitro and in vivo conditions

Background. Fluoride varnishes are commonly used in the prevention of caries. Objectives. To compare the newly introduced plates for mandibular condyle neck fracture treatment. Material and methods. The measured amounts of Colgate (R) Duraphat (R) 50 mg/mL Varnish Dental Suspension containing sodium fluoride 5% (22.600 ppm F) were applied on the teeth of 10 subjects and onto 30 specimens prepared from extracted human teeth. Levels of fluoride release in vivo study were assessed in unstimulated saliva at the baseline and after 1, 2 and 168 h from the application, and in vitro study after 1, 2, 24, 48 and 168 h from the baseline with the use of ion specific electrode. The specimens were immersed into artificial saliva with pH adjusted to 4, 5 and 7, 10 specimens per each medium, and stored in room temperature. Results. Under in vivo conditions, after 1 h following the application, the fluoride level increased 16-fold. After 2 h it slightly dropped to 15-fold higher, and after 168 h to 5-fold higher from the baseline (0.55 +/- 0.49 ppm). Under in vitro conditions, the cumulative fluoride release within 168 h was the highest to the medium with pH 4 (9.95 ppm), slight lower with pH 5 (9.39 ppm) and substantially lower with pH 7 (5.72 ppm). Regression analysis showed that fluoride release into artificial saliva was associated with time and pH; however, the acidity of the medium showed the higher impact than the time of release. Conclusions. The varnish released the maximum amount of fluoride to saliva within the first hours after application and the levels decreased at each period thereafter. Under in vivo conditions, a single application of the varnish maintained the salivary fluoride levels above the baseline up to 168 h, whereas under in vitro conditions the release of fluoride from the varnish was related to the acidity of the immersion medium.