Effect of Lateral Pressure Motion on the Torsional Behavior of Rotary ProTaper Universal Instruments

IntroductionThe purpose of this study was to evaluate the torsional behavior of rotary ProTaper Universal instruments after multiple clinical uses with and without lateral pressure motion.MethodsThirty sets of ProTaper Universal instruments were divided into 3 groups (n = 10): control group (CG) involving new instruments tested in torsion on the basis of ISO 3630-1, lateral pressure (LP) group involving instruments that were clinically used on 5 molars by using the shaping instruments S1 and S2 with lateral pressure motion, and no lateral pressure (NLP) group involving instruments that were clinically used on 5 molars without lateral pressure motion. The instruments in the LP and NLP groups were subsequently tested in torsion. Data were analyzed by using analysis of variance (α = 0.05).ResultsMultiple clinical uses caused a reduction in the maximum torque in the analyzed instruments. When the effect of using lateral pressure motion with the shaping instruments was assessed, a tendency of reduction in the maximum torque for the S1 and S2 instruments and of increase for the F1 and F2 instruments was observed in the group with lateral pressure motion.ConclusionsThe use of lateral pressure motion with the shaping instruments S1 and S2 tended to produce smaller decreases in the torsional resistance of the finishing instruments F1 and F2.