Model for assessment of carious lesion remineralization, and remineralization by a novel toothpaste.
This study is of a novel toothpaste which induced remineralization of carious lesions in specific pathogen-free Osborne-Mendel rats. Randomly distributed weanlings in 7 groups (n = 10) each were initially induced to develop carious lesions as a result of a severe dietary and bacteriological challenge. Thus, all were inoculated with S. mutans 10449S, ate diet 2000CS (containing 56% cornstarch) ad libitum, and, upon weaning and for 10 additional days, drank demineralized water supplemented to 10% (w/v) with sucrose (SW) ad libitum. During these 10 days, 6 of the 7 groups of rats were topically treated with a slurried F(-)-free placebo toothpaste. On the 10th day after initial inoculation, two groups were sacrificed, one which had been treated with the placebo and the one which had been untreated. The remaining groups were then provided unsupplemented demineralized water (DW), fed diet 2000CS, and topically treated with either of 5 coded toothpastes: a slurry of the F(-)-free placebo, a similar slurry of a conventional sodium fluoride toothpaste (Crest Regular) containing about 383 ppm F-, or one of three prototype toothpastes formulated by Enamelon, Inc. containing soluble calcium and phosphate salts. Two of these contained 377 ppm F- after mixing their components, either as sodium monofluorophosphate (E-MFP) or as NaF (E-NaF). The third prototype contained 0 ppm F- (E-w/o F). Test items were applied to the dentition for one minute/day, five days/week. These 5 remaining groups were sacrificed 13 days after the DW provision. After defleshing, heads were coded randomly and scored blindly for carious lesions. The exchange of DW for SW was associated with highly significant reductions of 10449S recoveries (p < 0.001), but there were no differences in recoveries among the groups as a function of toothpaste type. Total mandibular and maxillary sulcal and smooth surface caries scores were statistically significantly lower for the E-NaF-treated group at 23 days than for the 23-day placebo-, E-w/o F(-)-, and conventional NaF toothpaste-treated group. Reductions were most impressive quantitatively on approximal tooth surfaces, where both the E-MFP and E-NaF groups had the lowest scores, but were also statistically significant at sulcal surfaces for the E-NaF group. Thus, this study model can be used to detect significant remineralization effects, as occurred with the prototype toothpaste E-NaF.