Effect of repeated simulated clinical use and sterilization on the cutting efficiency and flexibility of Hyflex CM nickel-titanium rotary files.
BACKGROUND
Recent nickel-titanium manufacturing processes have resulted in an alloy that remains in a twinned martensitic phase at operating temperature. This alloy has been shown to have increased flexibility with added tolerance to cyclic and torsional fatigue. The aim of this study was to assess the effect of repeated simulated clinical use and sterilization on cutting efficiency and flexibility of Hyflex CM rotary files.


METHODS
Cutting efficiency was determined by measuring the load required to maintain a constant feed rate while instrumenting simulated canals. Flexibility was determined by using a 3-point bending test. Files were autoclaved after each use according to the manufacturer's recommendations. Files were tested through 10 simulated clinical uses. For cutting efficiency, mean data were analyzed by using multiple factor analysis of variance and the Dunnett post hoc test (P < .05). For flexibility, mean data were analyzed by using Levene's Test of Equality of Error and a general linear model (P < .05).


RESULTS
No statistically significant decrease in cutting efficiency was noted in groups 2, 5, 6, and 7. A statistically significant decrease in cutting efficiency was noted in groups 3, 4, 8, 9, and 10. No statistically significant decrease in flexibility was noted in groups 2, 3, and 7. A statistically significant decrease in flexibility was noted in groups 4, 5, 6, 8, 9, 10, and 11.


CONCLUSIONS
Repeated simulated clinical use and sterilization showed no effect on cutting efficiency through 1 use and no effect on flexibility through 2 uses.
Department of Endodontics, Keesler Medical Center, Keesler Air Force Base, Biloxi, Mississippi.
Scott T
ST
Seago
Department of Endodontics, Georgia Regents University, Augusta, Georgia.
Brian E
BE
Bergeron
Department of Endodontics, Keesler Medical Center, Keesler Air Force Base, Biloxi, Mississippi. Electronic address: timothy.kirkpatrick@us.af.mil.
Timothy C
TC
Kirkpatrick
Department of Endodontics, Keesler Medical Center, Keesler Air Force Base, Biloxi, Mississippi.
Mark D
MD
Roberts
Department of Endodontics, Keesler Medical Center, Keesler Air Force Base, Biloxi, Mississippi.
Howard W
HW
Roberts
Department of Endodontics, Louisiana State University, New Orleans, Louisiana.
Van T
VT
Himel
Department of Endodontics, Louisiana State University, New Orleans, Louisiana.
Kent A
KA
Sabey
D000818:Animals; D002417:Cattle; D005269:Femur; D008422:Materials Testing; D009532:Nickel; D018583:Pliability; D018915:Root Canal Preparation / Q000295:instrumentation*; D013242:Sterilization; D013696:Temperature; D014025:Titanium
C040654:titanium nickelide; D009532:Nickel; D014025:Titanium
Cutting efficiency; Hyflex CM; flexibility