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KMID : 0362320080330010054
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Journal of Korean Academy of Operative Dentistry
2008 Volume.33 No. 1 p.54 ~ p.65
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CYCLIC FATIGUE OF THE SODIUM HYPOCHLORITE TREATED AND /OR STEAM AUTOCLAVED NICKEL-TITANIUM ENDODONTIC FILES
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Cho Hye-Young
Jung Il-Young
Lee Chan-Young
Kim Eui-Seong
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Abstract
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The purpose of this study was to determine the effect of sodium hypochlorite and steam autoclaving on the cyclic fatigue of nickel-titanium endodontic files.
Two types of files with a .06 taper and 30 were used, K3 {(R)} (SybronEndo, Glendora, California, USA) and Hero 642 {(R)}(Micro-Mega, BesanCon, France).
The files were divided into 6 experimental groups containing 10 files each group depending the soaking time in 6% sodium hypochlorite solution and number of cycles of steam autoclave. After sterilization, a cyclic fatigue test was performed on each file, and the fracture time was recorded in seconds. The control group underwent the cyclic fatigue test only. After the test, the surface characteristics of the files were observed using scanning electron microscopy (SEM).
All groups containing the Hero 64~ files showed a similar cyclic fatigue fracture time. However, the cyclic fatigue fracture time with the K3 {(R)} files was significantly shorter in groups which were treated with sodium hypochlorite than in the control group (P < 0.05), SEM revealed both Hero 642 {(R)} and K3 {(R)} files to have significant corrosion on the file surface in groups treated with sodium hypochlorite, compared with the sharp and regular blades of the control group. K3 {(R)} files showed more corrosion than the Hero 642 {(R)} files. Bluntness of the blades of the K3 {(R)} file was observed in groups treated with steam autoclave. Although there was no obvious destruction on the surface of steam autoclaved Hero 642 {(R)} files, slight bluntness was observed.
Sterilizing with a steam autoclave is much less destructive to K3 {(R)} files than sodium hypochlorite. The longer time exposed to sodium hypochlorite, the more destructive pattern was shown on the blades of the files. Therefore, when using sodium hypochlorite solution, the exposure time should be as short as possible in order to prevent corrosion and increase the cyclic fatigue fracture time.
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KEYWORD
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Cyclic fatigue fracture, Ni-Ti endodontic files, sodium hypochlorite solution, steam autoclave
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