<b><i>Objective:</i></b> As a preventive measure, tin (Sn<sup>2+</sup>)-containing products have a great potential to prevent enamel surface loss during erosive challenges, but adverse effects of high Sn<sup>2+</sup> concentrations, such as astringent feeling of the teeth, are reported. Therefore, the main aim of this in vitro study was to develop a solution with lower Sn<sup>2+</sup> concentrations that can still prevent dental erosion. <b><i>Methods:</i></b> A total of 162 enamel specimens were prepared from human premolars, which were selected from a pool of extracted teeth. The specimens were randomly distributed to 9 groups (each group <i>n</i> = 18 enamel specimens) according to the different test treatments: a humid chamber (no treatment) as the negative control, the commercial Elmex® Erosion Protection mouth rinse as the positive control, and 7 solutions either with lower Sn<sup>2+</sup> concentrations and/or containing flavoring. The experiment included 4 cycles, consisting of pellicle formation by incubating the specimens with 200 μL of human saliva at 37°C for 1 h, then placing the specimens in the treatment for 2 min (60 mL, 30°C, shaking at 70 rpm), and later submitting them to an erosive challenge for 1 min in citric acid (60 mL 1%, pH 3.6, 30°C). Surface hardness was measured with a Vickers diamond and surface reflection intensity was measured with a reflectometer. <b><i>Results:</i></b> The control group performed significantly worse than all other solutions containing Sn<sup>2+</sup>. In general, there were no significant differences among the Sn<sup>2+</sup>-containing groups, and they presented similar protective effects on the enamel even when Sn<sup>2+</sup> concentrations were reduced and flavorings were added. <b><i>Conclusion:</i></b> Sn<sup>2+</sup> concentrations in mouth rinses may be lowered to 200 ppm without compromising the anti-erosive properties of the solution.