title: Does electropolishing improve the low-cycle fatigue behavior of a nickel-titanium rotary instrument in hypochlorite?
abstract: The purpose of this study was to compare the low-cycle fatigue (LCF) behavior of electropolished and nonelectropolished nickel-titanium (NiTi) instruments of the same design in hypochlorite. Forty-five electropolished and 62 nonelectropolished NiTi engine files were subjected to rotational bending at various curvatures in 1.2% hypochlorite solution. Number of revolutions to failure, crack-initiation sites, extent of slow crack extension into the fracture cross-section, and surface-strain amplitude were noted. A linear relationship was found between LCF life and surface-strain amplitude for both groups, with no discernible difference between the two (p > 0.05). No electropolished instrument showed more than one crack origin, significantly fewer than for the nonelectropolished instruments (p < 0.05). The square root of crack extension and strain amplitude were inversely related. Although surface smoothness is enhanced by electropolishing, this did not protect the instrument from LCF failure.
authors: Area of Endodontics, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, China. spcheung@hkusua.hku.hk
authors: Gary S P
authors: GS
authors: Cheung
authors: Ya
authors: Y
authors: Shen
authors: Brian W
authors: BW
authors: Darvell
mesh_terms: D003722:Dental Alloys / Q000737:chemistry*; D003775:Dental Polishing / Q000379:methods*; D004202:Disinfectants / Q000737:chemistry*; D004867:Equipment Design; D004868:Equipment Failure; D006801:Humans; D008422:Materials Testing; D009532:Nickel / Q000737:chemistry*; D018915:Root Canal Preparation / Q000295:instrumentation*; D012399:Rotation; D012973:Sodium Hypochlorite / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D003722:Dental Alloys; D004202:Disinfectants; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium; D012973:Sodium Hypochlorite