title: Experimental evaluation on the influence of autoclave sterilization on the cyclic fatigue of new nickel-titanium rotary instruments.
abstract: BACKGROUND
  The purpose of this study was to evaluate the effect of autoclave sterilization on cyclic fatigue resistance of rotary endodontic instruments made of traditional and new nickel-titanium (NiTi) alloys.
  
  
  METHODS
  Four NiTi rotary endodontic instruments of the same size (tip diameter 0.40 mm and constant .04 taper) were selected: K3, Mtwo, Vortex, and K3 XF prototypes. Each group was then divided into 2 subgroups, unsterilized instruments and sterilized instruments. The sterilized instruments were subjected to 10 cycles of autoclave sterilization. Twelve files from each different subgroup were tested for cyclic fatigue resistance. Means and standard deviations of number of cycles to failure (NCF) and fragment length of the fractured tip were calculated for each group, and data were statistically analyzed (P < .05).
  
  
  RESULTS
  Comparing the results between unsterilized and sterilized instruments for each type of file, differences were statistically significant (P < .05) only between sterilized and unsterilized K3XF files (762 versus 651 NCF). The other instruments did not show significant differences (P > .05) in the mean NCF as a result of sterilization cycles (K3, 424 versus 439 NCF; Mtwo, 409 versus 419 NCF; Vortex, 454 versus 480 NCF). Comparing the results among the different groups, K3 XF (either sterilized or not) showed a mean NCF significantly higher than all other files (P < .05).
  
  
  CONCLUSIONS
  Repeated cycles of autoclave sterilization do not seem to influence the mechanical properties of NiTi endodontic instruments except for the K3 XF prototypes of rotary instruments that demonstrated a significant increase of cyclic fatigue resistance.
authors.affiliation: Department of Endodontics I, Sapienza University of Rome, Rome, Italy. endo@gianlucaplotino.com
authors.forename: Gianluca
authors.initials: G
authors.lastname: Plotino
authors.forename: Alberto
authors.initials: A
authors.lastname: Costanzo
authors.forename: Nicola M
authors.initials: NM
authors.lastname: Grande
authors.forename: Renata
authors.initials: R
authors.lastname: Petrovic
authors.forename: Luca
authors.initials: L
authors.lastname: Testarelli
authors.forename: Gianluca
authors.initials: G
authors.lastname: Gambarini
mesh_terms: D003722:Dental Alloys / 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; D013242:Sterilization / Q000379:methods*; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium