الفهرس 
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Abstract
This study aimed to compare between the newly introduced Dia-PT NITI rotary system and the old one ProTaper Next rotary Ni-Ti files regarding the shaping ability, and canal centering ratio.
Shaping ability was evaluated via assessment of canal transportation, and canal centering ability. The mesiodistal transportation and centering ability were assessed by comparing pre-and post- instrumentation measurements taken on CBCT images at apical, middle, and coronal thirds.
Forty extracted permanent mandibular first molars were used to evaluate shaping ability. Teeth were decoronated at the cement-enamel junction using a diamond disc; then special measures were taken to ensure standardization and reproducibility of CBCT images. Samples were classified into two subgroups (n=20) according to file system.
Concerning shaping ability, the results showed that there was statistically significant difference between the two different rotary systems in canal transportation, and centering ability at the apical third of the canals which showed the highest value in Dia-PT sample.