الفهرس 
Influence of cross-section configuration of rotary ni-ti instruments on their cutting efficiency and surface topography
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Abstract
Aim of the study: The purpose of the study was to compare the cutting efficiency and surface wear of three rotary nickel titanium instruments namely; Twisted File system (TF), Revo-S system and Hero-Shaper system. Materials and methods: Sixty extracted mandibualr molar teeth were divided into three groups. The cutting efficiency of group I (Twisted file, TF), group II (Revo-S system) and group III (Hero- Shaper system) were compared. Also, the surface topography of the three systems before use, after one and after ten uses, were scanned using stereomicroscopy and scanning electron microscopy (SEM) and compared. Results: Results showed that there was no significant difference between the cutting efficiency of the three groups. In addition, results of the microscopic examination revealed that the unused Twisted Files showed manufacturing defects as metal rollovers, pitting and inclusions that worsen with usage. Whereas the surface of new Revo-S and Hero-Shaper files were free from defects. Defects as metal rollover, pitting, microfractures and ditching were more visible after ten uses and were more prevalent in the Revo-S files. One Revo-s file size SU fractured