Author/Authors :
Yazdizadeh, Mohammad Department of Endodontics - Dental School, Ahvaz Jundishapur University of Medical Science, Ahvaz , Skini, Masoumeh Department of Orthodontics - Dental School, Ahvaz Jondishapoor University of Medical Science , Hoseini Goosheh, Mohsen Department of Orthodontics - Dental School, Ahvaz Jondishapoor University of Medical Science , Jafarzadeh, Mansour Department of Endodontics - Dental School, Ahvaz Jundishapur University of Medical Science, Ahvaz , Shamohammadi, Milad Department of Orthodontics - Dental School, Ahvaz Jondishapoor University of Medical Science , Rakhshan, Vahid Researcher, Tehran
Abstract :
Introduction: Cyclic fatigue is the common reason for breakage of rotary instruments. This
study was conducted to evaluate the effect of cryogenic treatment (CT) in improving the
resistance to cyclic fatigue of endodontic rotary instruments. Methods and Materials: In
this in vitro study, 20 RaCe and 20 Mtwo files were randomly divided into two groups of
negative control and CT. CT files were stored in liquid nitrogen at -196°C for 24 h, and
then were gradually warmed to the room temperature. All files were used (at torques and
speeds recommended by their manufacturers) in a simulated canal with a 45° curvature
until breakage. The time to fail (TF) was recorded and used to calculate the number of cycle
to fail (NCF). Groups were compared using independent-samples t-test. Results: Mean
NCFs were 1248.2±68.1, 1281.6±78.6, 4126.0±179.2, and 4175.4±190.1 cycles, for the Mtwocontrol,
Mtwo-CT, RaCe-control, and RaCe-CT, respectively. The difference between the
controls and their respective CT groups were not significant (P>0.3). The difference
between the systems was significant. Conclusion: Deep CT did not improve resistance to
cyclic fatigue of the evaluated rotary files.
Keywords :
Cryogenic Treatment , Cyclic Fatigue , Instrument Fracture , Rotary Nickel Titanium Files
