title: [Mechanical properties of nickel-titanium files following multiple heat sterilizations].
abstract: OBJECTIVE
  The effect of cycles of sterilization procedures on nickel-titanium (NiTi) endodontic instruments is a serious concern for practitioners. There is no agreement in the literature whether these procedures could adversely affect the mechanical properties of endodontic files, and, consequently, increase the risk of intracanal failure. The purpose of this study was to evaluate the mechanichal resistance of Hero (MicroMega, Besancon, France) instruments, before and after sterilization procedures.
  
  
  METHODS
  Thirty 02, 04, 06 tapered Hero size 30 new instruments were chosen and divided into 3 groups. Group A (control) were tested according to ANSI/ADA Spec.no 28 for torsional resistance, angle of torque and angle at breakage (45 inverted exclamation mark ). Group B files were first sterilized with chemiclave for 10 cycles of 20 minutes at 124 inverted exclamation mark C and then tested as described above. Group C files were first sterilized with glass beads for 10 cycles of 20 sec. at 250 inverted exclamation mark C and then tested as described above. Data were collected and statistically analyzed (t-paired test). Differences among the 3 groups were statistically not significant for both tests.
  
  
  RESULTS
  All data were well within Spec.no 28 standard values.
  
  
  CONCLUSIONS
  From the results of the present study, we may conclude that repeated sterilization procedures do not adversely affect the mechanichal resistance of Hero files.
authors.affiliation: Cattedra di Materiali Dentar, Corso di Laurea in Igiene Dentale, Università degli Studi La Sapienza, Roma, Italy. luca_testarelli@hotmail.com
authors.forename: L
authors.initials: L
authors.lastname: Testarelli
authors.forename: L
authors.initials: L
authors.lastname: Gallottini
authors.forename: G
authors.initials: G
authors.lastname: Gambarini
mesh_terms: D003759:Dental Implantation, Endosseous, Endodontic / Q000295:instrumentation*; D008422:Materials Testing; D019563:Mechanics; D009532:Nickel; D013242:Sterilization / Q000379:methods*; D014025:Titanium
chemical_list: D009532:Nickel; D014025:Titanium