This study sought to evaluate whether remineralizing toothpastes can protect acid-softened enamel against further erosive episodes. Fifty enamel slabs of bovine teeth with preformed erosion-like lesions were randomly assigned to 1 control and 4 experimental groups (n = 10): group 1, nanohydroxyapatite (nanoHAp) dentifrice; group 2, arginine and calcium carbonate (CaCO3) dentifrice; group 3, potassium nitrate (KNO3) and high-fluoride (F) availability dentifrice; group 4, ordinary fluoridated dentifrice (OFD); and group 5, control (deionized water). Initial hardness measurements were taken after the different treatments were applied. Statistically significant mineral gains of 8.0% and 10.0% were exhibited in groups 1 and 4, respectively. Groups 2 and 3 showed mineral gains of 4.5% and 2.1%, respectively; these were not statistically significant. Group 5 showed mineral loss (-11.8%). A 1-way analysis of variance showed no statistically significant differences in the mean microhardness values among groups. However, there are indications that the nanoHAp and OFD toothpastes may decrease erosive lesions after treatment, while the arginine + CaCO3 and KNO3 + F pastes may prevent the progression of erosive lesions.