Objective: evaluate the loss of mass and the morphologic surface alteration of different cutting instruments after cavity preparation from dental structure and different methods of sterilization. Material and Method: standardized cavities in the buccal surface of bovine incisors had been carried through in the region of the limit enamel-cementum using five different types of cut instruments (n=4): Ca- cylinder carbide bur #56 (KG Sorensen), Kg- cylindrical diamond bur #1093 (KG Sorensen), Mi- cylindrical diamond bur #1093 (Microdont), Fa- cylindrical diamond bur #1093 (Fava) and Cv- cylindrical artificial diamond bur #8.2137 (CVDentUS). Each tip was submittes to a cycle that involved: Initial Scanning Electron Microscopy (SEM), cavity preparation (PC), clean-up ultrasonic (US), three methods of sterilization: glutaraldehyde 2% (Gl), dry heat (DH) or wet heat (WH) and final SEM. Results: significant difference for the interaction between factors was found. Conclusion: the sterilization method modifies structurally the cut instruments in different way among types of the instruments tested. Glutaraldehyde proved to be the worst method for sterilizing carbide bur. The diamond instruments showed great variability of results for the interaction of wear of cutting instruments and sterilization processes.