Influence of phase transformation on the torsional and bending properties of nickel–titanium rotary endodontic instruments

Abstract

The functional properties of nickel-titanium endodontic instruments, especially their flexible bending load level, were closely related to the transformation behaviour of the alloys.

The influence of heat treatment on the mechanical properties of Ni-Ti file materials

“…The detail of the equipment is described elsewhere 9,11,12) . The specimen was mounted on a movable stage, and the temperature of the specimen and equipment was kept at 37°C.…”

“…These special characteristics are derived from martensitic and austenitic transformations, with super-elasticity being observed at temperatures above the reverse transformation finishing point, A f 7) . Phase transformation behavior has an impact on the mechanical properties of Ni-Ti instruments [7][8][9][10][11] and is easily influenced by factors including chemical composition, heat treatment and manufacturing processes 4,6) . Previous studies reported heat-treated Ni-Ti alloy instruments had greater flexibility than instruments that had not been heat treated 7,11,12) .…”

Correlation between cyclic fatigue and the bending properties of nickel titanium endodontic instruments

“…An original cantilever bending test apparatus, introduced in the previous studies 18,19) , was used in this study. The cantilever bending test was performed to both instrument groups under the same conditions.…”

“…Many studies have been conducted to compare the separation resistance and/or analyze the cause of separation of various NiTi instrument systems [12][13][14][15][16] . Some of the procedures used include the cyclic fatigue test 17) , the bending test 18,19) , differential scanning calorimetry 20) , and the nano-indentation test 21) . Most studies using the cyclic fatigue test have used the method of continuously rotating the NiTi files until failure.…”

Resistência à fadiga flexural dos sistemas rotatórios k3 e Endosequence em razão do uso

“…Os trabalhos conduzidos com a finalidade de estudar as características geométricas dos instrumentos esclarecem que não é apenas um único fator que se pode atribuir às fraturas torsionais e sim, a ocorrência de diversos efeitos considerados isoladamente ou até mesmo simultaneamente (BERUTTI et al, 2003;HUBSCHER;MIYAI;EBIHARA;HAYASHI, 2006;PETERS et al, 2003;TURPIN et al, 2001 Fato preocupante é que esse tipo de fratura pode ocorrer mesmo não manifestando deformação prévia, pois muitas vezes as alterações micro-estruturais não podem ser visualizadas dificultando a prevenção da fratura. Cabe ressaltar aqui a importância dos trabalhos na tentativa de estabelecer critérios bem fundamentados para orientar o profissional no descarte dos instrumentos.…”