Surface Topography and Chemical Characteristics of Rotary Ni Ti Files of different manufacturing techniques after Multiple Use

Background: This study designed to evaluate and compare surface physical and chemical characteristics of recently introduced rotary NiTi files Neolix (Neolix, Châtres-la-Forêt, France), One Curve (Micro mega, France) and AF™ Blue S ONE File System (Fanta, USA) before and after 1st and 3rd use.
Materials and Methods: In this study thirty brand-new endodontic files having tip size 25/0.6 of the following systems were used: Neolix (Neolix, Châtres-la-Forêt, France), One Curve (Micro mega, France) and AF™ Blue S ONE One-File System (Fanta, USA). These files were equally divided into three groups (n=10). Ninety simulated curved canals (Endo Training Block-L; Dentsply Maillefer, Ballaigues, Switzerland) with curvature of 45º±10º, with 0.02taper, 0.15 mm apical diameter, and 16 mm length were used. File`s surfaces examined by Environmental Scanning Electron Microscope ESEM (FEI Quanta 250 FEG, Berlin, Germany) at 500X magnification before use. Cutting blade (active part) images been processed and their micrographs were analyzed at the tip, 2 and 4 mm short of its cutting tip. The Nickel (Ni) and Titanium (Ti) average contents (wt %) on the instrument`s surface were also analyzed before their use, using an Energy Dispersive Spectrometer Device (EDAX - AMETEK, Inc., Mahwah, NJ, USA). All instruments prepared using electric motor (Motor X-Smart Plus, Dentsply/Maillefer), following manufacturer`s instructions for each system. Each used file prepared three simulated canals, after each canal instrumentation, each file was removed for cleaning its flutes gently with sterile gauze, and for canal irrigation using with 2 mL/ 2.5% NaOCl irrigating solution. After the first and third instrumentation performed; files were cleaned, dried, stored and sent to SEM equipment for post-instrumentation files surface’s topography analysis and chemical composition of the NiTi content (wt %) according to the previously described pre-instrumentation analysis protocol. SEM micrographs recorded on a CD-ROM and projected for three blinded examiners’. They were given a spreadsheet including the instrument data (number, the location to be evaluated; tip, 0-2mm or 2-4mm from the tip) and the side of the instrument (detail facing up or down), and the criteria of defects and deformation assessment namely (irregular edges, grooves, micro-cavities and burrs).Data were recorded and statistically analyzed.
Results: Analysis of surface defects (SEM) showed that; all file systems have pre-instrumentation surface defects which increased after use. Neolix file had highest significant difference in all detected surface defects with One Curve file, with AF™ Blue S ONE file in burs and micro-cavities at file`s Tip and 0-2mm, in all examination intervals(p<0.05). One Curve file showed the least surface defects with significant difference with AF™ Blue S ONE file in edges mean values at file`s Tip at all examination intervals. EDS chemical analysis of Ni and Ti % revealed; decrease in Ni, Ti weight % after first and third uses. Decrease in Ni% was more than Ti%.
Conclusion: surface defects of the studied instruments were recorded before use, continuous use promoted their increase. Chemical change results revealed significant changes in Ni and Ti content on instruments surface after reuse led to that may affect their performance.