In vivo Study: Migration and Salivary Fluoride after Varnish Application

In vitro fluoride release experiments are often used to predict fluoride bioavailability of rosin-based fluoride varnishes, but these laboratory methods may not adequately reflect the behavior of these unique products in vivo. OBJECTIVE: The aim of this study was to measure migration and salivary fluoride levels following application of two rosin-based fluoride varnishes. METHODS: Consenting adult volunteers (n=19) with normal salivary flow were enrolled into this IRB-approved clinical study. This study utilized a randomized, single-blind, crossover design where all subjects received both products. Treatments consisted of a thin layer (50mg) of varnish applied to 8 tooth surfaces, preceded by >48hr fluoride-restricted period to clear residual fluoride from the oral cavity. Migration data were captured as subject self-assessments using a simple diagram at baseline, 90sec, 1hr, and 4hrs post-application. Salivary fluoride samples collected via Salivette® device at baseline, 1hr, and 4hrs post application were evaluated using a calibrated ISE. Products compared were: A) Vanish™ 5% NaF White Varnish (3M™ ESPE™), and B) EXM-736 (3M ESPE), the next-generation white varnish containing a functionalized calcium ingredient. RESULTS: Approximately 90sec after application, varnish was reported (mean±SEM) on: A) 9.79±1.67 and B) 9.21±1.42 surfaces, (ANOVA, p=0.79). After 1hr: A) 20.00±1.43 and B) 19.58±2.80 surfaces (p=0.88). After 4hrs: A) 16.68±1.53 and B) 17.21±1.90 surfaces (p=0.83). Mean salivary fluoride concentrations (ppm F±SEM) after 1hr: A) 3.12±0.90 and B) 3.36±1.09 (ANOVA, p=0.87). After 4hrs: A) 0.72±0.17 and B) 0.71±0.16 (p=0.96). CONCLUSIONS: Both varnish products exhibited elevated salivary fluoride levels for at least 4hrs, demonstrating that the functionalized calcium ingredient in EXM-736 does not adversely affect fluoride availability in vivo. Also, both varnishes exhibited similar ability to migrate from treated to untreated tooth surfaces and remain in place for at least 4hrs post-application, delivering fluoride across the dentition. This in vivo study emphasizes the importance of clinically-relevant evaluative methods.