الفهرس 
Review of literatureOnly 14 pages are availabe for public view
 |  | from | 16 |  |  |
| | | from | 16 | | |
Abstract
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 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