Purpose: To evaluate the efficacy of Clinpro XT in reducing dentin permeability and the stability of this effect after different acid challenges. Materials and Methods: Sixty-five roots of extracted human third molars were used. From each tooth, one dentin specimen was prepared and connected to a fluid filtration system to measure the dentin permeability after each of the following steps: sample preparation; treatment with 37% phosphoric acid; application of Clinpro XT; three acid challenges. Specimens were randomly assigned to 5 groups (n = 13) according to the acidic solution applied: Coca-Cola, natural lemon juice, wine vinegar, white wine and Red Bull energy drink. An additional 10 third molars were used to evaluate the degree of occlusion of the dentinal tubules and the surface roughness. Results: Clinpro XT statistically significantly reduced dentin permeability after just a single application. No statistically significant increase in dentin permeability could be detected after three consecutive challenges. The application of Clinpro XT promotes the occlusion of dentinal tubules and reduces the surface roughness. Conclusion: The Clinpro XT is effective in reducing dentin permeability. This effect persists even after acid challenges. Keywords: dentin, dentin permeability, dentin sensitivity