Coating Thickness Influences Fluoride Release from White Fluoride Varnish

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Objective:  Determine whether the coating thickness of OMNI's Vanish® Varnish 5% Sodium Fluoride White Varnish (Vanish) influences the amount of fluoride released in water over 24 hours. 

Method:  A thin (0.10mm), medium (0.23mm), and thick (0.52mm) coating of Vanish was coated onto resin-coated glass slides (n=10) in an area of 25 mm by 32 mm.   Each sample was immediately weighed and placed in 25mL DI water at 37^◦C.  After 1 hour, the water was collected and replaced with fresh DI water.  A 10mL aliquot of collected water was diluted 1:1 with TISAB II prior to fluoride analysis.  Buffered samples were evaluated using a calibrated fluoride ion selective electrode.  This procedure was repeated at 4, 7, and 24 hours.  Fluoride concentrations observed were converted to micrograms of fluoride and normalized to micro-grams of fluoride released vs. the coating weight for each slide.  Cumulative mean micrograms of fluoride released per gram of Vanish applied at each time-point were analyzed using two-way ANOVA at each collection time.  (T-test, p<0.05). 

Results:  The cumulative fluoride released per gram of sample in water at 37^◦C over time is shown below.  Thin coatings of Vanish release a greater percentage of total fluoride than thicker coatings.  The thinnest coating (0.10mm) slowly releases 100% of the total theoretical fluoride amount within 24 hours. 

Conclusion:  Thinner coatings of Vanish release statistically significant more fluoride per unit mass than thick coatings.  This suggests that only a thin coating is necessary to maximize the fluoride bioavailability and simultaneously minimize the amount of fluoride placed in the oral cavity.