الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 100 |  |  |
| | | from | 100 | | |
Abstract
Nickel-titanium rotary instruments have been developed with different properties and advancements to improve the quality of the root canal treatment. Rotary NiTi files separation had become a real concern because of their high frequency of tending an unexpected separation within the root canal during instrumentation.
This study was conducted on 120 mandibular mesio buccal canals. Specimens were randomly divided into two groups, part 1 assessing the effect of different obturation materials over apically separated instruments with different cross-sections. Part 2 assessing the bypass ability of apically separated instruments with different cross-sections. Part 1 (n=45) divided equally to 3 main groups according to the separated fragment type (PTN, PTU or Endostar) and then each group were divided equally to 3 subgroups according the type of obturating material (Biodentine, MTA or gutta-percha) (n=5). Part 2 divided equally to 3 groups PTN, PTU and Endostar (n=25). Specimens of each group were instrumented by its file system and files of size #25 were notched to a depth of half the instrument thickness with a disc at a point 3 mm from the tip of the instrument and then driven into the canals until the instrument is separated. Then in part 1 the apical microleakage was assessed by dye penetration method with methylene blue 2% for 48 hours then specimens were sectioned longitudinally by chisel and envaulted under the stereomicroscope while in part 2 the success of bypassing trials were evaluated by parallel radiograph technique.
The results of part 1 showed that there was no significant difference for the microleakage according to the of the separated file while there was a significant difference between the three obturation materials as the Biodentine showed the least amount of leakage followed by MTA and the gutta-percha showed the greatest amount of leakage. The results of part 2 showed that there was no significant difference between the three groups.