title: Machining efficiency and wear resistance of nickel-titanium endodontic files.
abstract: OBJECTIVE
  Nickel-titanium endodontic files are more flexible than stainless steel. Little information is reported concerning machining efficiency and wear resistance of nickel titanium. This study assessed the dentin-machining ability and wear resistance of nickel titanium endodontic files in vitro.
  
  
  METHODS
  The method described earlier to assess machining efficiency and wear resistance of stainless steel files was used. Eight different types and brands of nickel titanium files were studied: Ultra-Flex Hedström, Ultra-Flex K, Mity Hedstrom, Mity K, Mity Turbo, Hedstrom Naviflex NT, NiTiFlex, and Hyflex X-file. Thirty files of each brand were evaluated. One-way ANOVA and t tests were performed to analyze the data.
  
  
  RESULTS
  Considerable variation was found in matching efficiency and wear. The best initial machining ability of all nickel titanium instruments was recorded for the Hyflex-X file (0.60 +/- 0.16 mm2); the poorest performance was for the Mity Turbo file, which machined less than one third of the best performing instrument (0.19 +/- 0.12 mm2).
  
  
  CONCLUSIONS
  We compared our results with results of a previous study of stainless steel endodontic files and concluded that nickel titanium instruments are as aggressive as or better than stainless steel instruments in removing dentin. They are also more durable than their stainless steel counterparts.
authors: Department of Restorative Dentistry and Endodontology, University of Connecticut Health Center, School of Dental Medicine, Farmington, USA.
authors: R B
authors: RB
authors: Kazemi
authors: E
authors: E
authors: Stenman
authors: L S
authors: LS
authors: Spångberg
mesh_terms: D000704:Analysis of Variance; D003722:Dental Alloys / Q000737:chemistry*; D003762:Dental Instruments / Q000592:standards*; D003775:Dental Polishing; D003804:Dentin; D008422:Materials Testing; D008669:Metallurgy; D009532:Nickel / Q000737:chemistry*; D018915:Root Canal Preparation / Q000295:instrumentation*; D013193:Stainless Steel; D014025:Titanium / Q000737:chemistry*
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium