Purpose: The purpose of this in vitro study was to evaluate the effect of two preventive clinical treatments on bovine enamel susceptibility after erosive challenge induced by a soft drink. Materials and Methods: Eighteen sound bovine incisors were used for this study. Three experimental groups were assigned as follows: Group 1 was the control group; Group 2 specimens received a CPP-ACPF paste treatment; and Group 3 specimens received a treatment with a product containing 1% nano-hydroxyapatite and 455 ppmF-. The specimens were submitted to erosive challenge using a common soft drink (Coca Cola). The erosive activity on the enamel was evaluated by measuring surface microhardness change (Vickers method), surface roughness alterations and surface loss (vertical scanning interferometry (VSI) method). The data were statistically analysed using one-way analysis of variance (ANOVA) and Tukey's post-hoc test at a level of statistical significance a = 0.05. Results: The tested treatments exhibited significantly lower decreases in surface microhardness compared to the control group after the erosive challenge (p 0.05). The tested treatment groups did not show statistically significant lower increases in surface roughness compared to the control group (p > 0.05). In addition, the treatment groups exhibited statistically significant lower surface loss than the control group (p 0.05). Conclusion: Although the tested treatments reduced erosive activity, none of them provided complete protection against the development of enamel erosion, which means that they should be only used as a part of an individually tailored preventive programme. Keywords: enamel erosion, nano-hydroxyapatite, CPP-ACPF, soft drink