الفهرس 
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Abstract
This study aimed to evaluate and compared the effectiveness of manual K- file with PTN and Pro AF Baby Gold Ni-Ti rotary files, regarding the shaping ability via assessment of canal transportation and centering ability as well as their instrumentation time and cleaning efficacy via assessment of the scoring of the remaining ink in the canal.
The value of change in canal transportation and centering ratio were assessed by comparing pre- and post-instrumentation measurements taken on CBCT images in the buccolingual and mesiodistal direction. While the instrumentation time was measured using a digital chronometer. In addition, cleaning efficacy was evaluated using a stereomicroscope after clearing the teeth.
Seventy-two canals of (57) extracted primary molars were used in this study. The teeth were collected from the outpatients’ clinic of Pediatric Dentistry Department, Faulty of Dentistry, Ain Shams University and other private clinics with the following inclusion criteria:
1. Minimum apical resorption (presence of at least 2\3 of root length).
2. Patent root canal.
3. Absence of external, internal, and furcation resorption as assessed by CBCT.
4. Without any previous pulp therapy.
5. Mandibular primary molars with a single distal root canal.
The samples were classified into three main groups (n=24) canals according to the method of evaluation, then access cavities were done.
Shaping ability in term of canal transportation and centering ratio in three horizontal planes (coronal, middle, and apical) using pre and post CBCT images. Mesiodistal (M-D) and buccolingual (B-L) directions was measured on the axial sections at three levels; (2mm) between each level.
The instrumentation time of each group was measured using digital chronometer. Five canals were instrumented to overcome any bias in preparation due to operator fatigue. Total active instrumentation, instrument changes, and irrigation were measured, within each group.
Canal cleaning efficacy assessment was through clearing technique, and evaluation of the amount of the remaining ink in each canal at three levels (coronal, middle, and apical). Two blinded examiners assessed the scoring of cleaning efficacy from photographed were taken through a stereomicroscope.
Data were collected, then statistical analysis was performed.
Concerning canal transportation, our results showed no statistical significant difference between different groups or between values measured at different sections (coronal, middle, and apical) in both M-D and B-L directions. PAF showed the least coronal, middle and apical transportation in the M-D direction and the least apical transportation in the apical segment in the B-L direction. While PTN showed the highest B-L apical transportation followed by K-files. In M-D direction, both manual files and PTN files showed comparable transportation in the 3 horizontal planes.
Regarding the centering ratio, most results were satisfactory indicating no tendency for root canal deviation. Insignificant difference among the 3 files systems indicates their favorable use in primary molars.
Concerning cleaning efficacy, our result showed no statistical significant difference between different groups and values measured at three different sections. PTN and PAF showed the lowest mean value in the coronal and middle, while the three groups showed a high mean value in the apical third.
Finally, our result showed a statistical significant difference concerning instrumentation time between different groups. The highest instrumentation time was found in the manual K-files group, and the lowest value was found in the Pro AF Baby Gold group.