title: Torsional properties of stainless-steel and nickel-titanium files after multiple autoclave sterilizations.
abstract: This study tested the hypothesis that multiple sterilizations of endodontic stainless-steel and nickel-titanium files will lead to a continuous decrease in the resistance of files to separation by torsion. One hundred stainless-steel and 100 nickel-titanium #30 K-type files were divided into 20 groups of 10 and sterilized in increments of 10 cycles, using a full cycle and a fast cycle autoclave. These files were tested by twisting each of them in a clockwise direction until fracture (torque g-cm). Samples of the fractured files were embedded in an epoxy resin and polished for Knoop hardness tests. In addition, the samples were chemically etched to reveal changes in microstructure. The findings of this study indicate that neither the number of sterilization cycles nor the type of autoclave sterilization used affects the torsional properties, hardness, and microstructure of stainless-steel and nickel-titanium files.
authors.affiliation: Naval Dental Center, Okinawa.
authors.forename: B R
authors.initials: BR
authors.lastname: Hilt
authors.forename: C J
authors.initials: CJ
authors.lastname: Cunningham
authors.forename: C
authors.initials: C
authors.lastname: Shen
authors.forename: N
authors.initials: N
authors.lastname: Richards
mesh_terms: D000134:Acid Etching, Dental; D000704:Analysis of Variance; D003722:Dental Alloys / Q000737:chemistry*; D004853:Epoxy Resins; D004867:Equipment Design; D004868:Equipment Failure; D006244:Hardness; D006358:Hot Temperature; D006801:Humans; D016014:Linear Models; D008422:Materials Testing; D009532:Nickel / Q000737:chemistry*; D018915:Root Canal Preparation / Q000295:instrumentation*; D013193:Stainless Steel / Q000737:chemistry*; D013242:Sterilization / Q000379:methods*; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D014102:Torsion Abnormality
chemical_list: D003722:Dental Alloys; D004853:Epoxy Resins; C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium