Effect of fluoride concentrations on overdenture abutments

This study evaluated the preventive effect of four concentrations of fluoride. Twenty-five extracted caries-free anterior teeth from patients aged 50-70 were prepared as overdenture abutments. The teeth were sectioned mesiodistally into two halves. The teeth were covered with a protective varnish, leaving a window on the root surface and one on the cut dentin of the occlusal. The root halves were randomly divided into 5 groups of 10 specimens and each group received a different 5-minute topical treatment prior to being placed in the demineralizing solution. The treatments were: Group 1: distilled H2O only; Group 2: 100 ppm F-, Group 3: 250 ppm F-, Group 4: 500 ppm F-; and Group 5: 1000 ppm F-. The teeth were cycled for 6 hours in a demineralizing solution and for 17 hours in a fluoride-free remineralizing solution. The cycling was maintained for 10 days. The root halves were sectioned and prepared for histologic examination. The depth of the lesions were measured from standardized photo-micrographs by means of a sonic digitizer. The conclusions were: (1) the lesions on the root surface were too small to be measurable, (2) the lesions on dentin were all of similar depth, and (3) the lesions had bands within them and the width of these bands showed a dose response to the fluoride concentration of the topical application.