Enamel Fluoride Uptake of Fluoride Varnish Prototypes

Objectives: To evaluate the fluoride uptake into artificially lesioned bovine enamel of five fluoride-containing test varnishes formulated using cellulose and/or acrylate polymers, a reference positive control fluoride varnish and fluoride placebo.
Methods: Enamel specimens were prepared from sound bovine teeth and embedded in the end of plexiglass rods. Artificial lesions were formed by exposure at 37oC to a lesion-forming solution for 24hr. Eight specimens per group were placed into a neoprene stopper and a single layer of varnish (approx. 0.0050 ± 0.001 g) was applied to the enamel surface. The stopper was placed in a specimen cup, varnish-treated enamel surfaces facing up. A multi-channel peristaltic pump was set to provide a slow drip of Artificial Saliva solution (1.0 ml/min) over the stopper. The solution in contact with the enamel specimens was slowly replaced by fresh solution, mimicking intraoral salivary flow. The specimens were removed from the stopper after 24hr. and excess varnish was removed with a spatula and ethanol. The specimens were then rinsed with DI water for 30 seconds. One layer of enamel was removed from each specimen by immersion in 0.5 mL of 1.0 N HClO4 for 15 seconds. A sample of each solution was buffered to a pH of 5.2. The fluoride content was then determined using FDA #40 procedure.
Results: Statistical one-way analysis of variance model and Student-Newman-Keuls pairwise analysis were used. EFU concentrations (PPM) were: (Prototype 1, 5931 ± 267), (Prototype 2, 4195 ± 306), (Prototype 3, 5116 ± 353), (Prototype 4, 3883 ± 416), (Sample 5 - Placebo, 72 ± 4), (Sample 6 - positive control, 3388 ± 207) and (Prototype 7, 1131 ± 95).
Conclusions: All varnish prototypes were deemed to be effective at promoting EFU when compared to the positive control except for prototype 7.
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