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Abstract
The present study investigated the effect of multiple sterilization cycles on the topographical surface changes, cutting efficiency of RaCe electropolished and non-electropolished rotary Nickel titanium instruments. With twenty four file, size 35, 0.06 taper, and 25mm in length as received from the manufacture subjected to one, three and six sterilization cycles respectively. First part evaluated the topographic surface changes after application of different sterilization cycles. Presence of surface changes was assessed by scanning electron microscope (SEM) at X- 100 and X- 500 magnification to explore the surface defects. Adobe photoshop CS5 software was used to calculate the % of surface alteration on both electropolished and non electropolished RaCe instruments The result of the first part of study showed the presence of manufacturing defects in the as received condition of both types of instruments including pitting, debris, minimal surface cracks, and metal sparks. For RaCe electropolished instruments: no statistically significant difference was found when comparing between mean surface changes % of instrument sections (tip, apex, middle and cervical) at each sterilization cycles. For RaCe non- electropolished instruments: there was a statistically significant difference between file sections at different sterilization cycles. File tip showed the highest mean percentage change, followed by the apical section, which showed lower mean % change. There was no statistically significant difference between middle and cervical sections; both showed the statistically significantly lowest mean % change