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The defects created in commercial dental alloys during blasting with alumina particles propelled in compressed air under pressure 0.1 and 0.4 MPa have been studied using positron annihilation spectroscopy,scanning electron microscopy and X-ray diffraction.It was observed that higher pressure causes the increase in roughness and damaged zone range.The type of defects was determined as vacancies on dislocations.The defect concentration decreases with the depth and depends on alloys\' type and applied pressure.The Rutherford backscattering spectroscopy and variable energy positron beam studies indicate shallow alumina deposition in material and show that small pressure of 0.1 MPa is not enough to remove metal surface oxides completely in 60 s in all studied dental alloys.