The aim of the present study was to evaluate the effect of fluoride mouthrinses, supplemented or not with sodium trimetaphosphate (TMP), on the dental erosion of the enamel using an artificial mouth. Material and Methods: 120 blocks of bovine enamel were randomly distributed in 5 groups according to the following mouthrinses: Placebo (without fluoride or TMP), 100 ppm F, 225 ppm F, 100 ppm F + 0.2% TMP micrometric and 100 ppm F + 0.2% nanosized TMP. The blocks were subdivided into 2 experimental treatments (1 or 3 days). Each erosive cycle consisted of 7 exposures to citric acid (each 4 s), alternated with 6 exposures to artificial saliva (each 7 s), three times a day. Treatment with mouthrinses was performed after the first and last erosive cycle of each day for 1 min. The blocks were analyzed by profilometry method, surface hardness and longitudinal section analyses, as well as surface free energy (Ys). Data were analyzed by two way ANOVA, Student-Newman-Keuls test and Pearson's correlation coefficient (p <0.05). Results: In general, a significantly greater protective effect was observed for mouthrinses containing TMP in relation to the hardness and wear of the enamel, with an additional effect for the use of nanoparticles. There was a moderate correlation between surface hardness and longitudinal section (r = -0.533; p <0.001). In addition, a reduction of s and its apolar component (YsLW) and electron donor sites (γ¯) were observed in the groups treated with TMP containing mouthrinses. In addition, significant differences were observed for most of the variables analyzed in relation to the duration of the erosive protocol (1 and 3 days). Conclusions: The treatment with mouthrinses with TMP reduced significantly the erosive enamel wear and the mineral loss compared to non-TMP mouthrinses, and such effects may be related to changes in the Ys parameters. The artificial mouth used in this study was adequate for the enamel erosive studies under in vitro conditions.