Purpose: To assess the influence of multiple clinical uses on the torsional behavior of ProTaper Universal rotary NiTi instruments
N= 10 sets of instruments ProTaper Universal instruments S1, S2, F1 and F2
•Ten sets of instruments were used by an experienced endodontist, each set being used in five molar teeth.
•After clinical use (by crown down technique with speed of 300 rpm and torque of 5 Ncm), instruments were analyzed for damage by optical and scanning electron microscopy.
•The used instruments were subjected to torsional test and compared with 10 sets of new instruments.
Most highlighted Results:
•The ProTaper Universal rotary were used by experienced endodontists for cleaning and shaping of 5 molars without fracture.
•The maximum torque for instruments S2, F1 and F2, were significantly lower following clinical use, as well as the angular deflection at fracture for instruments S2 and F1 .
when reusing Protaper Universal instruments, lower torque settings should be considered and complex canal systems (narrow, extremely curved ) should be avoided.
weakness: the complexity of the treated teeth and degree of canal curvature were not specified.