Prevalence of defects and fractures in nickel-titanium instruments after single use in patients

Abstract

Abstract We investigated defects and fractures in nickel-titanium, engine-driven, endodontic instruments/files that had been single-used in patients` mandibular and maxillary molars. A total of 169 instruments [n = 113 ProTaper Next® (PTN) (Dentsply Maillefer, Ballaigues, Switzerland), and n = 56 Reciproc® (R) (VDW, Munich, Germany)] were analyzed using scanning electron microscopy. A single operator had used the instruments under a standardized protocol in one patient`s molar. Two trained and calibrated evaluators analysed three locations for each instrument. For non-fractured instruments, each location/third (apical/medium/coronal) received one of the classifications: i) intact (no plastic deformation/no defect), or ii) crack and/or deformation/unwinding. For fractured instruments, the area of fracture was classified in: i) cyclic fatigue mode, or ii) shear mode (torsional fatigue). Chi-square test calculated frequency of defects. PTN and R presented the same low frequency of defects after one clinical use in patients` molars by the same dentist. Defects appear equally in apical, medium, and coronal – except for X3 PTN that had more defects in the coronal part. Only one clinical fracture occurred, with an X3 PTN instrument: a torsional fatigue fracture originated in a crack. It is appropriate to use either PTN or R, in a single use, to treat root canals of patients` molars.