Diamond burs of various manufactors with the same shape and grit of ISO-classification show differences in cutting efficiancy and signs of wear. This study sought to compare the cutting efficiancy of different diamond burs after 10 to 40 min of continious operation. Two groups of diamont burs with different diameter were set up. Group 1 contained 8 burs with similar cylindrical shape, diameter of 1,6mm and diamond coarseness (105-125 μm grit) of different manufactors. One of the evaluated burs had additional cooling grooves. Group 2 contained 11 burs with similar cylindrical shape, diameter of 1,2mm and diamond coarseness (105-125 μm grit) of different manufactors. Two of the evaluated burs had additional cooling grooves. Five burs of each type have been selected. They were evaluated using a high-speed handpiece set at 200000 RPM with a coolant flow rate of 50 ml/min mounted on a custom testing device. The burs were tested under constant load (152g+2g) while performing cuts on standardized 99,5% pure Al2O3 ceramic block (AD-995, Coors Tek Inc.) Each bur was subjected to four consecutive cuts for 10 to 40 min continious operation. Cutting efficiancy was measured in milimeters by dephts in the ceramic blocks. The mean wear rates were determined for five burs of each type and compared with analysis of variance with p Schlagwörter: Diamantierte Schleifkörper, Standfestigkeit, Schleifleistung