الفهرس 
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Abstract
The aim of the study was to evaluate the shaping ability of 2 different reciprocating NiTi files (RPC blue and M3-L platinum). In terms of preserving canal curvature, centering ratio and canal transportation. Forty extracted human permanent mandibular molars, completely mature intact without caries or abnormal morphology, having moderate curvature 25° - 35° were collected, and randomly divided into 4 groups 10 each. Radiographic imaging were taken pre and post root canal preparation by CBCT machine to determine degree of curvature according to Schneider’s method and to measure the changes in dentin thickness of the canal at 3, 6 and 9 mm from the root apex. Percent of reduction of canal curvature was calculated according to the following equation: [(pre-instrumentation measurement) – (post-instrumentation measurement)] / (pre-instrumentation measurement) x 100. Degree of transportation and centering ratio in mesiodistal direction was calculated according to Gambill et al, using this equation: [(M1-M2) - (D1-D2)] to measure transportation while [(M1-M2) / (D1-D2)] to measure centering ratio. The results showed that there was no statically significant difference in the four-studying groups. While for group B (RPC blue with glide path), there was a statically significant decrease in canal curvature after preparation. Equally important, with comparison between amounts of changes in the four-studying groups, there was no statistically significant difference showed regarding canal transportation. While regarding centric ratio there was a statistically significant difference showed. Despite these promising results, questions remain, Reciprocating Endodontics versus Rotary Endodontics. There is abundant room for further progress in determining the answers we need.