الفهرس 
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Abstract
This study aimed to compare and evaluate the effectiveness of Manual K files, Kedo S-Square rotary files, Kedo SG Blue rotary file regarding the remaining dentin thickness and their cleaning efficacy through assessment and scoring the remaining ink in the canals.
The value of the remaining dentin thickness was assessed by comparing pre- and post- instrumentation taken by CBCT images. In addition, cleaning efficacy was assessed using a stereomicroscope after clearing the teeth.
Thirty upper second primary molars were collected for this study. Mesio-buccal and palatal canals were only prepared by the files. Teeth were extracted due to orthodontic purposes or because of their delayed retention, with the following inclusion criteria.
• Minimal apical resorption with at least 2/3 root length or 7-10 mm.
• Patent root canal.
• Absence of external or internal root resorption or furcation involvement.
• Without any previous pulp therapy.
The samples were classified into three main groups, were each group contains 10 teeth (20 canals), they were mounted in horse-shoe putty indices made up of silicone based-high viscosity impression material. Caries removal and access cavities were done then canal instrumentation was carried out.
Remaining dentin thickness was measured through superimposition of pre- and post CBCT images. Measurements were calculated in axial plane at three levels: coronal, middle, and apical.
Canal cleaning efficacy assessment was conducted through clearing technique, and evaluation of the amount of the remaining ink in each canal. Two blinded examiners assessed the scoring of cleaning efficacy from photographs were taken through a stereomicroscope.
Data was collected, then statistical analysis was performed. Results concerning the remaining dentin thickness showed a statistically significant difference between different groups. The amount of dentin removed was more by manual k files than the rotary ones, while Kedo S-SG showed the least amount of dentin removed.
Results of cleaning efficacy measurements showed statistically significant difference between the three groups, where manual K files showed the least cleaning efficacy, followed by Kedo S- Square the Kedo S SG blues which showed the best cleaning efficacy.