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Comparison of three topical fluorides using computer imaging.

The purpose of this in vitro study was to evaluate the short and long-term effectiveness of fluoride varnish and compare it with the two most commonly used topical fluorides, i.e., fluoride gel and foam. A second purpose of the study was to compare the effectiveness of these preparations on primary and permanent teeth. Enamel slabs with a thickness of 500 microns were obtained from caries free primary molars and premolars. They were divided into four groups: control, foam (F), gel (G) and varnish (V). Fluorides were applied to the enamel slabs according to the manufacturer's instructions and were placed in a 5.1 pH acidic gel for one week. The amount of demineralization from the enamel was measured by calculating the amount of light reflected from these surfaces. This was done by using a Charged Couple Device attached to a high resolution microscope with image processing software, Optima 5.22. The enamel slabs were placed in a freshly prepared acidic gel for a second week without application of fluorides. This was done to mimic a situation where fluoride is eventually brushed away from teeth. Reflective images were recorded under the previously described conditions. A two-way analysis of covariance was used to compare the treatments. The results showed no statistically significant difference (with Bonferroni correction) in the effectiveness of different fluoride preparations over the short-term (Week I comparison; p-values: F vs. G 0.079, F vs. V 0.030, G vs. V 0.44). However, the long-term protection provided by fluoride varnish was far more than fluoride gel and foam (Week II comparison; p-values: F vs. G 9X10-5, F vs. V 7X10-8, G vs. V 1X10-4). Fluorides were equally effective for both primary and permanent enamels (p-value 0.24). The results of this study suggest that fluoride varnish is beneficial for use with white spot lesions, newly erupted permanent teeth and early decalcification in primary dentition.