الفهرس 
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Abstract
The aim of the study was to evaluate the shaping ability of Revo-S, M-Pro and 2Shape rotary systems in moderately curved canals regarding the change of canal curve, canal transportation and canal centering ability.
Thirty human mandibular molars were selected for the study, with moderate angle of curvature between (25o-35o). Samples were randomly and equally distributed into three groups each of ten according to the system used for mesiobuccal canal preparation. Cone beam computed tomography was used to evaluate angle of canal curvature and dentin thickness pre and post instrumentation. Dentin thickness was measured at three different levels 3,6 and 9 mm from the apex at axial view using measuring tool.
Canal angle was determined according to scheinder method and percentage of canal curve reduction was determined according to following equation
(Pre instrumentation measurement - post instrumentation measurement )/(Pre instrumentation measurement) X100
Canal transportation and centering was calculated according to following equations
Degree of transportation in mesio-distal direction was calculated using the folllowing equation
(Ml-M2) - (D 1 - D2).
Centering ratio was calculated for all groups mesio-distally using the following formula:
(M1-M2) / (Dl-D2).
Where:
M1: Shortest distance between the mesial margin of uninstrumented canal and external root surface.
D1: Shortest distance between the distal margin of uninstrumented canal and external root surface.
M2: Shortest distance between the mesial margin of the instrumented canal and external root surface.
D2: Shortest distance between the distal margin of the instrumented canal and external root surface
Results showed that there was a statistically significant difference between different groups in percentage of reduction of canal curve. The highest values of percentage of reduction was found in Revo-S group followed by 2Shape, while the lowest value was for M-Pro group.
There was a statically significant difference between mean transportation values of different groups. M-pro group presented the highest mean transportation value in mesial direction among all groups.
There was no significant difference in the values of centering ratio in different systems.