BACKGROUND It is very important for a clinician to know the increased wear of mechanized files when establishing endodontic therapy. The aim of this study was to check the wear of the Primary WaveOne file upon shaping two, four and six maxillary molar vestibular canals. METHODS The deterioration of 40 files, divided into four groups, was evaluated microscopically: group 1, control (unused); group 2, two canals; group 3, four canals; and group 4, six canals. After instrumentation, the files were embedded in resin and sectioned at their apical third into three equal parts. To analyze the wear of edges in the different sections, AutoCAD software was used and analysis of variance (ANOVA) was then performed to compare the mean rake angles. RESULTS The files with two and four uses showed slight wear, whereas those with six applications showed significant wear (p<0.05). CONCLUSIONS Primary WaveOne files can be used in up to four root canals without their edges losing effectiveness. Key words:Files wear, reciprocating motion, shaping capacity, WaveOne.