Fatigue resistance of rotary ProTaper Universal instruments after use with and without lateral pressure motion

Aim: To evaluate the fatigue resistance of rotary ProTaper Universal instruments after multiple clinical uses with and without lateral pressure motion. Methods: Thirty sets of ProTaper Universal (PTU) instruments (Dentsply-Maillefer, Ballaigues, Switzerland), types S1, S2, F1 and F2, totaling 120 files, were analyzed and divided into three groups, as follows: Control Group (CG), with 10 sets of new instruments, which were fatigue tested until rupture to determine their fatigue resistance; Lateral pressure (LP), with 10 sets of instruments, each set used clinically in five mandibular and maxillary molars (15 to 20 canals) using shaping instruments with lateral pressure motion; and No-Lateral Pressure (NLP), with 10 sets of instruments, each set used clinically in five mandibular and maxillary molars (15 to 20 canals) using shaping instruments without lateral pressure motion. The instruments in the LP and NLP groups were subsequently fatigue tested. Data were analyzed using analysis of variance (α = 0.05). Results: Multiple clinical uses caused a reduction in the fatigue life of the analyzed instruments. When the effect of employing lateral pressure motion with the shaping instruments was assessed, a tendency for the consumed fatigue life to be higher for the S1 and S2 instruments in LP and for the F1 and F2 instruments in NLP was observed. Conclusion: The use of lateral pressure motion with the S1 and S2 PTU instruments during the shaping of curved root canals tended to decrease the consumption of the fatigue life of F1 and F2 instruments.Uniterms: Endodontics. Root canal therapy. Dental instruments.