Effect of environment on low-cycle fatigue of a nickel-titanium instrument.
This study examined the low-cycle fatigue (LCF) behavior of a nickel-titanium (NiTi) engine-file under various environmental conditions. One brand of NiTi instrument was subjected to rotational-bending fatigue in air, deionized water, sodium hypochlorite, or silicone oil. The curvature of each instrument, diameter of the fracture cross-section, and the number of rotations to failure were determined. The strain-life relationship in the LCF region was examined by using one-way analysis of variance, and the number of crack origins with chi2, for differences between groups. The results showed a linear relationship, on logarithmic scales, between the LCF life and the surface strain amplitude; regression line slopes were significantly different between noncorrosive (air, silicone oil) and corrosive (water, hypochlorite) environments (P < .05), as well as number of crack origins (P < .05). Hypochlorite was more detrimental to fatigue life than water. In conclusion, environmental conditions significantly affect the LCF behavior of NiTi rotary instruments. Fatigue testing of NiTi engine-files should be in a service-like environment.
Area of Endodontics, Faculty of Dentistry, University of Hong Kong, Hong Kong SAR, China. spcheung@hkusua.hku.hk
Gary S P
GS
Cheung
Ya
Y
Shen
Brian W
BW
Darvell
D000388:Air; D000704:Analysis of Variance; D003343:Corrosion; D003722:Dental Alloys; D003762:Dental Instruments; D003799:Dental Stress Analysis; D004868:Equipment Failure; D009532:Nickel; D018583:Pliability; D012044:Regression Analysis; D018915:Root Canal Preparation / Q000295:instrumentation*; D012827:Silicone Oils; D012973:Sodium Hypochlorite; D014025:Titanium; D014867:Water
D003722:Dental Alloys; D012827:Silicone Oils; D014867:Water; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium; D012973:Sodium Hypochlorite