Objective: The purpose of this study was to assess the effects of topical fluoride agents on enamel erosion in vitro. Method and materials: Ten premolars extracted for orthodontic purposes were sectioned buccolingually and then longitudinally into two parts, so that four specimens were obtained from each tooth. The specimens were randomly assigned to one of four groups. The following topical fluoride agents were applied to the specimens: 1% titanium tetrafluoride (0.32 MF) for 1 minute; Duraphat (2.26% F) and Elmex (1.25% F) for 4 minutes. In the control group, no solution was applied. The specimens were treated with an artificial caries solution for 4, 8, 12, and 16 days. Calcium (Ca++) concentration was determined by an atomic absorbtion spectrophotometer, while fluoride (F-) concentration was determined with an ion-selective electrode. One-way analysis of variance tests were performed on cumulative concentrations of calcium and fluoride at days 4, 8, 12, and 16. Results: Specimens treated with titanium tetrafluoride lost significantly less calcium than did specimens in the other two test groups at all time periods. Titanium tetrafluoride-treated specimens released significantly less fluoride than did Duraphat- or Elmex-treated specimens at day 16. Conclusion: Titanium tetrafluoride was found to be more effective than the other fluoride agents in preventing artificial enamel lesion formation.