LAUSR

AIM To evaluate the torsional properties of the NiTi glide path reciprocating instruments R-Pilot (VDW, Munich, Germany) and WaveOne Gold Glider (Dentsply Sirona, Ballaigues, Switzerland). METHODOLOGY Ten R-Pilot (size 12.5, .04 taper) and 10 WaveOne Gold Glider (size 15, .02v taper) instruments were used. The torque and angle of rotation at failure of new instruments (n = 10) were measured according to ISO 3630-1. Three millimetres of each instrument tip was clamped to a small load cell by a lever arm linked to the torsion axis. The fracture surface of all fragments was examined with a scanning electron microscope. Data were analysed using the Student t-test at a significance level of P < 0.05. RESULTS The maximum torsional strength of the R-Pilot instruments was greater than the WaveOne Gold Glider (P < 0.05). In contrast, WaveOne Gold Glider instruments had significantly higher angular rotation to fracture than R-Pilot instruments (P < 0.05). The scanning electron microscopy of the fracture surfaces revealed similar and typical features of torsional failure (ductile type) for both brands. The torsional failure displayed two zones: the first with microvoids in the centre of the instruments (core) and the second one represented by plastic deformation around the microvoids; this configuration occurred because of the shear stresses originated during the twisting. CONCLUSIONS R-Pilot instruments had a lower angle of rotation to fracture but a higher torque to failure than WaveOne Gold Glider instruments.