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Secondary caries (SC) is the most common reason for restoration failure. Objectives: The purpose of this study was to determine the efficacy of a fluoride-containing varnish in inhibiting progression of early SC. Methods: 48 human premolars were used, on which a 1x4x1.5 mm cavity was prepared and restored with amalgam. Incipient SC lesions were initially developed in 4 days using a microbial caries model. Half of each specimen was then painted with an acid-resistant nail varnish to maintain the baseline lesion. Specimens were then divided into 4 groups, and were either not treated (group 1, control) treated with a placebo varnish (group 2; 0 ppm F; removed after 24h), a fluoride varnish (group 3; Duraphat, Colgate; removed after 24h), or a topical 1.23% APF gel (group 4; Oral B; applied for 4 min) prior to being subjected to 4 more days of bacterial challenge. At the end of the study, specimens were analyzed using Quantitative Light-Induced Fluorescence (QLF), sectioned, stained with Rhodamine B, and analyzed using confocal laser scanning microscopy (CLSM) to determine the extent of the baseline and treated lesions in each specimen. Results: CLSM data indicated that the control group (#1) had significantly deeper lesions than the Duraphat group (#3), and numerically deeper lesions than groups 2 and 4. Surface lesion depth change (treated minus baseline lesion data; mean ± SEM) for groups 1, 2, 3 and 4 was: 39.46±8.04, 3.73±6.47, -18.25±16.56, 23.05±7.08, respectively. Wall lesion depth and QLF data followed a similar pattern. Conclusions: The results from this study suggested that the application of a fluoride varnish to an active SC lesion significantly slowed down lesion progression. Furthermore, the application of a placebo varnish also showed a trend towards slowing down lesion progression, suggesting that the effect of fluoride varnish on SC is not only due to its fluoride release. |