title: Correlation between cyclic fatigue and the bending properties of nickel titanium endodontic instruments.
abstract: The effects of cyclic fatigue on bending properties of NiTi endodontic instruments were investigated. Sixteen Profiles(®) were divided into two groups (A, and B). The sequence of cantilever bending test and cyclic fatigue test was alternated repeatedly until file separation occurred. In the cyclic fatigue test, the instrument curvature was 19° in group A and 38° in group B. Fractographic examination was performed to determine fracture patterns. In group A, there were significant differences between the bending load values measured before the cyclic fatigue test and the last cantilever bending test before instrument fracture at each deflection (p<0.05). Fractographic examination showed the specific patterns of cyclic fatigue fracture. The stress required to induce martensitic transformation might be reduced due to the softening behavior caused by the cyclic fatigue under the relaxation condition of the superelasticity range (group A). The SEM images were able to display specific patterns indicating cyclic fatigue fracture.
authors.affiliation: Pulp Biology and Endodontics, Department of Oral Sciences, Medical and Dental Sciences Track, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU).
authors.forename: Jindan
authors.initials: J
authors.lastname: Piao
authors.forename: Kana
authors.initials: K
authors.lastname: Miyara
authors.forename: Arata
authors.initials: A
authors.lastname: Ebihara
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Nomura
authors.forename: Takao
authors.initials: T
authors.lastname: Hanawa
authors.forename: Hideaki
authors.initials: H
authors.lastname: Suda
mesh_terms: D003762:Dental Instruments; D004708:Endodontics / Q000295:instrumentation*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D009532:Nickel; D014025:Titanium
chemical_list: C040654:titanium nickelide; D009532:Nickel; D014025:Titanium