Fracture Resistance for Fatigue Cyclical Nickel - Titanium Endodontic Instruments – Literature Review

Background: rotary endodontic instrument fractures have been related as a major problem in Endodontics due to the complications that follow such incidents. Objective: The aim of this review was to evaluate, through traditional literature review, the factors that influence fracture resistance of endodontic NiTi instruments used in mechanical preparation and shaping of the root canals. Methods: The review was made by two independent reviewers and the following electronic databases were used: PUBMED Central, BVS/BIREME, Web of Science, Science Direct, Higher Level Personnel Improvement Coordinator (CAPES) Periodic Portal , The Cochrane Library and PROSPERO, from 1988 to 2014.Results: the number of cycles to which rotary NiTi instruments have been submitted showed that fracture resistance is directly related to fracture resistance; composition and thermomechanical processing of the alloy and transverse cross sections and dimensions. Conclusions: Fracture resistance seems to be related to the number of cycles that an instrument is able to resist after a given load conditions. Kinematic motion, alloy composition, different rotational angles and the speed used, as well as the shape and area of the cross section of the straight instrument, are the main fracture causes.