The purpose of this study was to selectively remove the smear layer from dentine without altering the underlying tissue. Two groups of test samples were established. The first group consisted of flat dentine surfaces exposed transversely in the mid-coronal plane using a diamond blade. The second group was comprised of Class II cavity preparations made in recently extracted molar teeth using a diamond bur. The cut surfaces in both groups were subjected to the air polishing action of the Prophy Jet devise. Exposure times were 2, 5, 10, 20 and 40 s. An untreated control was established for each group. The specimens were examined by scanning electron microscopy. Findings showed the selective removal of the smear layer can occur in 5 s for surfaces perpendicular to the jet stream while axial walls of cavity preparations required 20 s. The method confirms previous findings and can be recommended to study the influence of the smear layer in dentine bonding.