Restor Dent Endod.  2012 May;37(2):79-83.

Effect of internal stress on cyclic fatigue failure in .06 taper ProFile

• Jung HR
• Kim JW
• Cho KM
• Park SH

Abstract

OBJECTIVES
The purpose of this study was to evaluate the relation between intentionally induced internal stress and cyclic fatigue failure of .06 taper ProFile.
MATERIALS AND METHODS
Length 25 mm, .06 taper ProFile (Dentsply Maillefer), and size 20, 25, 30, 35 and 40 were used in this study. To give the internal stress, the rotary NiTi files were put into the .02 taper, Endo-Training-Bloc (Dentsply Maillefer) until auto-stop by torque controlled motor. Rotary NiTi files were grouped by the number of induced internal stress and randomly distributed among one control group and three experimental groups (n = 10, Stress 0 [control], Stress 1, Stress 2 and Stress 3). For cyclic fatigue measurement, time for separation of the rotary NiTi files was recorded. The fractured surfaces were observed by field emission scanning electron microscope (FE-SEM, SU-70, Hitachi). The time for separation was statistically analyzed using two-way ANOVA and post-hoc Scheffe test at 95% level.
RESULTS
In .06 taper ProFile size 20, 25, 30, 35 and 40, there were statistically significant difference on time for separation between control group and the other groups (p < 0.05).
CONCLUSION
In the limitation of this study, cyclic fatigue failure of .06 taper ProFile is influenced by internal stress accumulated in the files.

Keyword

Auto-reverse; Auto-stop; Cyclic fatigue failure; Internal stress; Separation; .06 tper ProFile

MeSH Terms

Electrons
Fatigue
Intention
Torque

Figure

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  Figure 1 Representative image of cyclic fatigue testing using inclined glass plane.

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  Figure 2 FE-SEM micrographs of separated surface of .06 taper ProFile. The surfaces in all experimental groups showed same patterns of cyclic fatigue fracture. There is no circular abrasion mark which is feature of surface of torsional fracture. (a) #30 Stress 3 group (×200); (b) #35 Stress 3 group (×200). Black arrow, initiation zone; white arrow, overload zone. FE-SEM, Field emission scanning electron microscope.

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