An in situ interproximal model for studying the effect of fluoride on enamel.

This crossover study determined the ability of an interproximal, intra-oral model to demonstrate a fluoride dose response to 0-, 250- and 1,100-ppm fluoride (sodium fluoride) dentifrices with respect to fluoride uptake into, and remineralization of, incipient subsurface enamel lesions. Following a 1 week 'lead in' period during which 30 panelists were randomly assigned to use one of the products, two enamel specimens with artificial carious lesions were mounted into a specially designed functional partial denture worn by each panelist. Panelists continued to brush three times daily with their test dentifrice for 4 weeks, after which the specimens were removed and analyzed for fluoride uptake and remineralization. The procedure was repeated until each panelist had followed all three treatment regimens. Fluoride analyses were performed using a microdrill biopsy technique, and mineral content changes were determined by transverse microradiography. Fluoride uptake data were significantly different (p < 0.01) for all three products with the effect of 1,100 ppm F > 250 ppm F > placebo. The 1,100 ppm F dentifrice also effected significantly greater remineralization (p < 0.01) than did the 250-ppm-F or placebo dentifrices. Relative efficacy of the three fluoride dentifrices tested in this study was similar to that established in a clinical trial, and, therefore, supports the use of this model for in situ studies of the effects of fluoride-containing products on enamel lesions.