To evaluate the effect of a fluoride varnish on demineralization and remineralization of root surfaces in vitro.

This study describes salivary fluoride levels after topical fluoride gel application on overdenture abutments. Fluoride levels were evaluated separately for the subjects with normal unstimulated salivary flow rate (n = 16) and for those with a low flow rate (n = 8). One drop of fluoride gel (Karigel-N, Lorvic) was placed in two abutment depressions of the duplicated overdenture, after which unstimulated whole saliva was collected for 30 minutes. Samples for fluoride analysis were taken at 5-minute intervals. Two additional samples were taken at 45 and 60 minutes. Fluoride concentration at the abutment-denture interface (remaining fluoride concentration) was measured at the end of the study. Salivary fluoride concentrations decreased gradually in both groups of subjects, but after 1 hour they remained at a higher level in subjects with low flow rates. Subjects' salivary flow rates correlated negatively with remaining fluoride concentration at the denture-tissue interface. Consequently, mean remaining fluoride concentration was significantly higher in subjects with low flow rate than in their normal counterparts.

To evaluate the effect of topical fluoride gels on the microhardness of three glass ionomer cements.

Teeth prepared as overdenture abutments are susceptible to caries, and it has been shown that brushing by itself is not sufficient to prevent this process. This study evaluated the preventive effect of a remineralization gel which has a low fluoride concentration and compared its effects with those of a phosphate fluoride gel (Karigel), which has a much higher concentration of fluoride. Twenty extracted anterior teeth from patients aged 50 to 70 years were prepared as for overdenture abutments. Each tooth was sectioned into three fragments. An acidified gel system was used to produce artificial caries lesions on the occlusal and root surfaces of each fragment. One fragment of each tooth was treated with the remineralizing gel, the second fragment with a high-fluoride gel, and the third fragment served as the control. Ten teeth were removed at two weeks and again at four weeks, and were sectioned and prepared for histological examination. The depth of the lesions was measured from standardized photomicrographs by means of a sonic digitizer. The conclusions were: (1) Lesions on the occlusal tended to be deeper than those on the root surfaces at four weeks but not at two weeks; and (2) the high-fluoride gel was more protective than the low-fluoride remineralizing solution at both time periods on the occlusal but not on the root surface.