Saad al Shammary¹, Mohammed Osama²,Amani El-SayedBadr^3.   Ab Complete removal of tissue, debris, and microorganisms is goal in endodontic treatment. These goals are met by biomechanical instrumentation of the root canal and by developing a continuously tapering canal from while keeping the apical opening as small as practical1. During instrumentation to achieve these goals, dentin within the canal system is in contact with instruments of varying taper and cross-sectional shapes. The removal of dentin chips during the time that the instrument is contacting dentin produced the canal shape.