Fracture and deformation of ProTaper Next instruments after clinical use

BACKGROUND: The aim of this study was to evaluate the fracture and defects observed in ProTaper Next files discarded after a normal clinical use. MATERIAL AND METHODS: 571 ProTaper Next rotary instruments were collected after clinical use from the clinic of endodontics over 12 months. The length of the files was measured using a digital caliper to determine any fracture, later all the files were evaluated under a stereomicroscope to observe defects such as unwinding, curving or fracture. The data obtained were analyzed using a chi-square and z test. RESULTS: 13.83% of the discarded files showed defects, the most frequent defect was fracture (7.53%). The highest rate of fracture was observed in the X1 (17.04) files (19.87%). The presence of deformations without fracture was also more frequent in the 17.04 file (11.8%). CONCLUSIONS: Because of the relatively high incidence of deformation of smaller files, these instruments should be considered as a single use. It is important not to exceed the maximum uses recommended by the manufacturer to reduce the risk of cyclic fatigue, the main cause of fracture of the files (79.07%). It is also important to observe each file after use to discard small defects or fractures. Key words:Clinical use, deformation, fracture, M-Wire, ProTaper Next.