Objective: To compare in vitro the remineralizing effects of different regular dentifrices and whitening dentifrices (containing pyrophosphates) on predemineralized enamel. Method and Materials: Specimens from 84 bovine incisors were embedded in epoxy resin, partly covered with nail varnish, and demineralized in a lactic acid solution (37°C, pH 5.0, 8 days). Parts of the demineralized areas were covered with nail varnish, and specimens were randomly assigned to 6 groups. Subsequently, specimens were exposed to a remineralizing solution (37°C, pH 7.0, 60 days) and brushed 3 times a day (1:3 slurry with remineralizing solution) with 1 of 3 regular dentifrices designed for anticaries (group 1, amine; group 2, sodium fluoride) or periodontal (group 3, amine/stannous fluoride) purposes or whitening dentifrice containing pyrophosphates (group 4, sodium fluoride). An experimental dentifrice (group 5, without pyrophosphates/fluorides) and a whitening dentifrice (group 6, monofluorophosphate) served as controls. Mineral loss and lesion depths were evaluated from contact microradiographs, and intergroup comparisons were performed using the closed-test procedure (alpha =.05). Results: Compared to baseline, specimens brushed with the dentifrices containing stannous/amine fluorides revealed significant mineral gains and lesion depth reductions (P .05). Concerning the reacquired mineral, the whitening dentifrice performed worse than the regular dentifrices (P > .05), while mineral gain, as well as lesion depth, reduction was negligible with the control groups. Conclusion: Dentifrices containing pyrophosphates perform worse than regular dentifrices but do not necessarily affect remineralization. Unless remineralizing efficacy is proven, whitening dentifrices should be recommended only after deliberate consideration in caries-prone patients. Schlagwörter: artificial caries, dentifrices, enamel, fluoride, in vitro, remineralization, tooth whitening, transversal microradiography