Enamel remineralization and fluoride uptake from 5000 ppm fluoride pastes

Prescription-based fluoride formulations are recommended for those patients most at-risk for caries formation and progression. The efficacy of these 5000 ppm fluoride formulations, however, can vary depending on the formulation, and this in turn may impart significant differences in product performance. OBJECTIVE: The purpose of this research was to determine the ability of 5000 ppm fluoride (NaF) pastes in remineralizing weakened enamel emulating early caries formation. METHODS: 3mm diameter bovine enamel specimens were prepared in the usual manner and initially softened in a carbopol-lactic acid solution [White, DJ: Caries Res 21 1987 228-42] for a period of 36hrs (37°C). Following initial softening, specimens (N=10) were stratified (mean VHN =35) into the following groups: (a) distilled (DI) water (negative control), (b) Prevident, (c) ControlRx, or (d) Modified ControlRx (containing calcium) and cycled (10 days) in a lesion reversal model consisting of four two-minute treatments (diluted 1:3 with DI water) and one four-hour acid challenge (carbol-lactic acid, pH = 5.0) per day. Between these events, specimens were immersed in artificial saliva [ten Cate, et al.: Caries Res 22 1988 20-6]. After 10 days of cycling, surface microhardness and enamel fluoride uptake were evaluated. RESULTS: Mean surface microhardness recoveries (±SEM) were (a)-6.54±1.38, (b)6.54±1.96, (c)93.08±6.05, and (d)136.70±9.03 with a < b < c < d (ANOVA, pairwise multiple t-tests, p>0.05). Fluoride uptake measurements (±SEM) were (a) 245.8±11.6, (b) 2510.9±181.4, (c) 6858.4±444.6, and (d) 8634.2±311.7 with a < b < c < d (ANOVA, pairwise multiple t-tests, p>0.05). CONCLUSIONS: The model was sensitive to fluoride's rehardening benefits as demonstrated by statistical differences between the DI water and both ControlRx and Prevident. Remineralization and fluoride uptake from the Prevident formulation was found to be statistically inferior to both ControlRx and Modified ControlRx. The Modified ControlRx paste exhibited greater rehardening than the unmodified ControlRx.