TY - JOUR
T1 - Mechanical Properties of Various Heat-treated Nickel-titanium Rotary Instruments
AU - Goo, Hye Jin
AU - Kwak, Sang Won
AU - Ha, Jung Hong
AU - Pedullà, Eugenio
AU - Kim, Hyeon Cheol
N1 - Publisher Copyright:
© 2017 American Association of Endodontists
PY - 2017/11
Y1 - 2017/11
N2 - Aim The purpose of this study was to compare the bending stiffness, cyclic fatigue, and torsional fracture resistances of heat-treated and conventional nickel-titanium rotary instruments. Methods V-Taper 2 (VT2; #25/.08), V-Taper 2H (V2H; #25/.06), Hyflex CM (HCM; #25/.06), HyFlex EDM (HDM; #25/variable taper), and ProTaper Next X2 (PTN; #25/variable taper) were tested. The bending stiffness was measured with the customized device (AEndoS), and the files (n = 15) were fixed at 3 mm from the tip and bent at 45° with respect to their long axis. Cyclic fatigue resistance was tested by pecking and rotating instruments (n = 15) in artificial canal with a 7.8-mm radius and 35° angle of curvature until fracture. The ultimate torsional strength and toughness were estimated by using AEndoS. The file tip of 5 mm was fixed between resin blocks and driven clockwise at 20 rpm until fracture. The results were analyzed by using one-way analysis of variance and Duncan post hoc comparison. The fracture surfaces and longitudinal aspect of each group were examined under the scanning electron microscope. Results CM-wire instruments had lower bending stiffness than others. HDM showed the highest cyclic fatigue resistance, followed by VTH and HCM (P <.05). VT2 showed the highest ultimate strength, followed by HDM, VTH-PTN, and HCM. HDM and VT2 showed significantly higher toughness than VTH, HCM, and PTN (P <.05). Scanning electron microscope analysis showed typical fractographic features of cyclic fatigue and torsional fractures. Conclusions CM-wire instruments showed higher flexibility and cyclic fatigue resistance than M-wire and conventional nickel-titanium instruments. Large cross-sectional area and conventional nickel-titanium showed high torsional resistance.
AB - Aim The purpose of this study was to compare the bending stiffness, cyclic fatigue, and torsional fracture resistances of heat-treated and conventional nickel-titanium rotary instruments. Methods V-Taper 2 (VT2; #25/.08), V-Taper 2H (V2H; #25/.06), Hyflex CM (HCM; #25/.06), HyFlex EDM (HDM; #25/variable taper), and ProTaper Next X2 (PTN; #25/variable taper) were tested. The bending stiffness was measured with the customized device (AEndoS), and the files (n = 15) were fixed at 3 mm from the tip and bent at 45° with respect to their long axis. Cyclic fatigue resistance was tested by pecking and rotating instruments (n = 15) in artificial canal with a 7.8-mm radius and 35° angle of curvature until fracture. The ultimate torsional strength and toughness were estimated by using AEndoS. The file tip of 5 mm was fixed between resin blocks and driven clockwise at 20 rpm until fracture. The results were analyzed by using one-way analysis of variance and Duncan post hoc comparison. The fracture surfaces and longitudinal aspect of each group were examined under the scanning electron microscope. Results CM-wire instruments had lower bending stiffness than others. HDM showed the highest cyclic fatigue resistance, followed by VTH and HCM (P <.05). VT2 showed the highest ultimate strength, followed by HDM, VTH-PTN, and HCM. HDM and VT2 showed significantly higher toughness than VTH, HCM, and PTN (P <.05). Scanning electron microscope analysis showed typical fractographic features of cyclic fatigue and torsional fractures. Conclusions CM-wire instruments showed higher flexibility and cyclic fatigue resistance than M-wire and conventional nickel-titanium instruments. Large cross-sectional area and conventional nickel-titanium showed high torsional resistance.
KW - Bending stiffness
KW - CM-wire
KW - cyclic fatigue
KW - electro discharge machining
KW - NiTi rotary file
KW - torsional fracture resistance
UR - http://www.scopus.com/inward/record.url?scp=85029754808&partnerID=8YFLogxK
U2 - 10.1016/j.joen.2017.05.025
DO - 10.1016/j.joen.2017.05.025
M3 - Article
C2 - 28951028
AN - SCOPUS:85029754808
SN - 0099-2399
VL - 43
SP - 1872
EP - 1877
JO - Journal of Endodontics
JF - Journal of Endodontics
IS - 11
ER -