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Abstract
The purpose of the study was to compare the surface changes and mechanical properties of 2 different rotary NiTi instruments: Protaper and BioRaCe rotary systems were used. They are different in design and taper and surface condition. Eight sets of each rotary NiTi systems were used in this study. Each single file of each system was examined under the scanning electron microscope (SEM) before (as received from the manufacturer) and after 4 clinical uses in the mesio-buccal canals of fully formed roots of permanent mandibular first molar (group I). Cantilever bending and stiffens properties were determined for each file within each system before and after clinical uses (group II). This was done by the universal testing machine. Each main group was further subdivided into 2 subgroups according to the file system used: Subgroup A: 48 files (8sets) of Protaper file system were used to prepare the teeth. Subgroup B: 48 files (8sets) of BioRaCe file system were used to prepare the teeth. The data were statistical analyzed