The work concerns the analysis of influence of the wear process of endodontic instruments on the mechanical and physico-chemical properties of the materials from which they are made. A detailed study of the microstructure, mechanical properties and corrosion resistance in the environment simulating work of the tool was conducted. The research was done for the new Mtwo endodontic files and after six times of use. In addition, the observations with a scanning electron microscope in order to reveal possible damage caused by the impact of a corrosive environment were carried out. The results showed that use of the tool by six times revealed damage at the edges of the blades and may cause a lack of continuity of the cutting line resulting in the uneven distribution of the resistive force which acts on the tool during operation.