Objectives: The purpose of this study was to evaluate the changes in dentinal permeability (i.e. hydraulic conductance) after prophylactic treatments performed using prophy-powders with air-polishing system or prophy-pastes on exposed middle dentine. The changes in dentine morphology were evaluated by SEM. Study design: Commercial prophylactic pastes and air-polishing powders were tested in this study. Dentine discs from human third molars were used to study the quantitative reduction of the dentine permeability under simulated pulpal pressure (20 cm H 2O). Further specimens were gold-coated and analysed using observed a SEM. Results: The results of this study showed different dentine permeability redaction based on the type of product employed (i.e. prophylactic paste or air-polishing powders). The use of Sylc bioactive glass and sodium bicarbonate were the most effective in reducing dentine permeability of the specimens. However, the air-polishing procedures performed with Sylc bioactive glass created a dentine surface devoid of exposed dentinal tubules due to the presence of a compact multilayered smear layer. Colgate Sensitive Pro-Relief and Nupro NU-Solution reduced the dentine permeability up to 69.8% and 66.9% respectively. Conclusion: Although all the tested products are able to statistically reduce dentine permeability, Sylc bioactive glass is an innovative and effective product which completely occludes the dentinal tubules during prophylactic procedures of air-polishing. © Medicina Oral S. L.