Abstract
Materials and Methods Forty-five files from each brand were randomly assigned to three groups (n = 15) and subjected to the following: no immersion (control), 1-minute immersion, and 5-minute immersion in 2.5% NaOCl at 37°C. CF for all the files was tested within a well-lubricated stainless-steel artificial canal in a water bath at 37°C simulating body temperature. The procedure was video recorded, and the number of cycles to fracture (NCF) was calculated by multiplying the time taken to fracture, with the number of rotations per second. The data were analyzed for normality, and thereafter, one-way ANOVA with multiple Bonferroni was used as the post hoc test. Results The resistance to CF of OC files was significantly higher than PTG files in all groups. In groups immersed in NaOCl for one minute, OC files showed significant drop in the CF resistance; PTG files showed a drop as well but not significantly. Both files demonstrated a significant drop in resistance to CF after immersion in NaOCl for five minutes compared to the control group. Conclusion OC files were significantly more resistant to CF compared to PTG in all groups. Immersion in 2.5% NaOCl for 5 minutes significantly reduced the resistance to CF for all the files.
Highlights
Present day nickel-titanium (NiTi) rotary files are used for root canal cleaning and shaping mainly because of their superelasticity [1]
For the purpose of this study, a testing device was made of a stainless-steel block fixed to a main frame. e steel block was machined according to the recommendations of Larsen et al [25] and Haikel et al [26] and possessed a simulated root canal, 25 mm in length, with a single curvature of 60° and 5 mm radius that was engraved into the block to a depth of 1.5 mm. e length of the canal was verified by inserting a K-file size 15. e steel block was covered with a removable glass plate to help
It was observed that the files of the One Curve (OC) group had higher number of cycles to fracture (NCF) than the files of the ProTaper Gold (PTG) group regardless of immersion protocol. e multiple Bonferroni tests showed that the PTG-5-min NaOCl had significantly lower NCF than all other groups except for PTG-1-min NaOCl. e PTG-1-min NaOCl group had a higher NCF than the PTG-5-min NaOCl and a lower NCF than the PTG-control group
Summary
Present day nickel-titanium (NiTi) rotary files are used for root canal cleaning and shaping mainly because of their superelasticity [1]. E aim of the study was to assess the resistance to cyclic fatigue of the two nickel-titanium (NiTi) files, One Curve and ProTaper Gold, after immersion in NaOCl solution (2.5%) at body temperature for varying time intervals.
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