Abstract
Introduction: The aim of this study was to determine the effect of thermal treatment on the flexural
resistance of mechanically pre-fatigued rotary nickel-titanium (NiTi) endodontic instruments.
Methods: New and mechanically pre-fatigued rotary NiTi instruments were subjected to thermal
treatments at 350˚C, 400˚C and 450˚C for 30 minutes, and then were rotated in a fatigue-testing
device until fracture. The time to fracture was recorded and multiplied by the number of rotations
per minute to obtain the number of cycles to failure (NCF) for each group.
One-way analysis of variance (ANOVA) followed by Tukey–Kramer multiple-comparison post hoc
test was used for the comparison between the different tested groups. Fractographic examination by
scanning electron microscopy was also performed to study the morphological characteristics of the
fractured instruments.
Results: Statistical analysis showed that the thermal treatment at or below 400˚C of the new files
did not improve the resistance to the flexural fatigue. Also, the flexural fatigue resistance of mechanically
pre-fatigued files was significantly lower than that of new files. However, with thermal
treatment significant improvement in the resistance to flexural fatigue was achieved, especially at
450˚C (P < 0.05).
Conclusion: Thermal treatment seems to be of significance in improving the cyclic fatigue resistance
or life span of fatigued or used NiTi files.
| Original language | English |
|---|---|
| Pages (from-to) | 145 |
| Number of pages | 150 |
| Journal | Endo |
| Publication status | Published - 2011 |