الفهرس 
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Abstract
Summary
The aim of the study was to evaluate the concept of using a
single file retreatment technique in comparison to multiple
files retreatment technique where the parameters to be
evaluated were the amount of residual filling material on
the root canal dentin and the time required for retreatment.
master apical file was inserted in the canal, the root was
ground from the buccal aspect with carborundum disc until
the file appears along the whole length of the canal so
longitudinal section of the canal was obtained.
Three types of time records were evaluated until the
complete removal of gutta percha. In all-time records of
the time taken for handling of instruments, changing of
files, irrigation, etc. was excluded.
A total of sixty human permanent mandibular molars were
used in this study. Access cavities were done and special
measure were taken to ensure standardization and
reproducibility of samples.
The samples were divided into two groups according to the
type of file used. Group I (n=30) where the mesiobuccal
canal will be retreated with the ”One shape” file and Group
II (n=30) where the mesiobuccal canal will be retreated
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with the rotary sequence of ”R-endo” (R1, R2 and
R3).Then each group was divided into A and B subgroups
where A subgroups represents the curvatures below 25
degrees and B subgroups represent the curvatures above 25
degrees.
Amount of remaining gutta percha assessment:
The portion of the roots that had the largest area of the root
canals and the largest quantity of filling debris were
selected for scanning using stereomicroscope to analyze the
amount of remaining filling material in each group at
coronal, middle and apical portions, using a fixed
magnification of x20. Images were captured using a digital
camera fitted on the microscope, and then transferred to
desktop and saved as JPEG format. ImageJ Software was
used to analyze the obtained images. No attempt was made
to distinguish between residual filling material and sealer.
Time required for retreatment assessment:
First; time required for reaching the original working length
(T1), the time elapsed from entering the canal with the first
instrument until reaching the original working length was
measured using a stopwatch. Second; time required for
removal of filling material (T2), the time required for
removal of root canal filling material from starting the first
Summary and Conclusion
115
instrument until the completion of the re-instrumentation
were recorded. Third; the total time for retreatment
(T1+T2), time required for reaching the working length and
for removal of obturation material and sealer from starting
the first instrument until the completion of the reinstrumentation
were calculated.
Results:
Concerning the amount of remaining gutta percha:
The One shape file was better in removing the gutta percha
than R- Endo system. Both coronal and middle thirds
showed less reminants than the apical third. Moreover, The
curvatures of roots below 25 degrees showed less reminants
than above 25 degrees.
Concerning the time required for retreatment:
The one shape file showed less time required for
retreatment than the R-Endo system. Both Curvatures either
below or above 25 degrees showed no statistically
difference.
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116
Conclusion:
1. The single file concept proved to be an efficient way
for removal of gutta percha in retreatment cases.
2. Both single and multiple files systems failed to
completely remove all the gutta percha in retreatment
cases where further instrumentation is needed for
total removal.
3. The gutta percha in apical one third was inefficiently
removed by both systems in comparison to the
middle and coronal thirds.
4. The angle of curvature had an effect on the
efficiency and time of single file system and multiple
files system in retreatment procedure.
Recommendations:
1. Further studies can be employed to assess the
performance of the proposed single file concept
technique in retreatment procedures such as
transportation, post operative pain, file fracture and
debris extrusion.
2. Further researches to be employed to assess the use
of adjunctive aids as solvents with One shape file for
more efficient removal of gutta percha in retreatment
procedures & to concern different radii of curvature