Comparative analysis of mechanical properties of differently tapered nickel-titanium endodontic rotary instruments

This study aimed to compare the mechanical properties of differently-tapered EndoWave nickel-titanium endodontic rotary instruments (size #30/0.04 taper and #30/0.06 taper; Group 0.04 and 0.06, respectively). Torsional and bending properties were evaluated with the cyclic fatigue test and the cantilever bending test, respectively. Canal transportation was assessed following instrumentation of curved canals in resin blocks. Torque and apical force during instrumentation were determined using an automated instrumentation and torque/force analyzing device. The number of cycles to fracture was Group 0.04>Group 0.06 (p<0.05). The bending load values were Group 0.06>Group 0.04 (p<0.05). Group 0.04 better maintained the original canal shape compared with Group 0.06. The median clockwise torque value was Group 0.06>Group 0.04 (p<0.05), whereas no significant differences were detected in the median counterclockwise torque and apical force values (p>0.05). Under the present experimental condition, 0.04- and 0.06-tapered EndoWave instruments exhibited different mechanical properties.