title: Evaluation of the Fractured Surface of Five Endodontic Rotary Instruments: A Metallurgical Study.
abstract: BACKGROUND
  The aim of this study was to compare several metallurgic properties of Neoniti instrument with four other commonly used endodontic rotary files.
  
  
  METHODS
  Neoniti A1 (25/0.08), RaCe (25/0.06), Mtwo (25/0.06), Twisted file (25/0.06) and ProTaper Next X2 (25/0.06) were examined by differential scanning calorimetry (DSC) before and after heat treatment at 500°C. X-ray diffraction (XRD) was also performed on the specimens. Furthermore, scanning electron microscopy (SEM) and x-ray energy-dispersive spectrometric (EDS) analyses were carried out on randomly selected fractured files.
  
  
  RESULTS
  In SEM tests, dimpled ruptures, characteristic of ductile fracture, were seen in all evaluated cross sections of all files. The SEM results of all evaluated files were alike. EDS results revealed higher proportions of Nickel (Ni) rich intermetallic compounds in Neoniti; whereas, in all the other files the proportion of Titanium (Ti) rich precipitates was higher. DSC results indicated that the temperature present in the oral environment, the austenite phase existed in all files. Mtwo and RaCe files did not show austenite transformation in the temperature range evaluated in this study. Only Neoniti revealed rhombohedal phase (R-phase) transformation. After heat treatment. No significant difference was seen in the transformation temperatures of all evaluated files. XRD evaluations revealed that Neoniti contained both Ni-rich and Ti-rich precipitates. The amount of the martensite phase was higher in ProTaper Next.
  
  
  CONCLUSIONS
  The metallurgic properties of Neoniti files were different from other evaluated rotary files. This file contained higher proportions of Ni-rich precipitates.
authors: Department of Endodontics, Dental School, AJA University of Medical Sciences, Tehran, Iran; ; Department of Endodontics, Dental School, Tehran University of Medical Sciences, Tehran, Iran.
authors: Mohsen
authors: M
authors: Aminsobhani
authors: Material Science and Engineering Department, Sharif University of Technology, Tehran, Iran.
authors: Mohamad Saleh
authors: MS
authors: Khalatbari
authors: Department of Endodontics, Dental School, Tehran University of Medical Sciences, Tehran, Iran.
authors: Naghmeh
authors: N
authors: Meraji
authors: Department of Endodontics, Dental School, Tehran University of Medical Sciences, Tehran, Iran.
authors: Abdollah
authors: A
authors: Ghorbanzadeh
authors: Department of Physics, Science School, Central Tehran branch of Azad University, Tehran, Iran.
authors: Ehsan
authors: E
authors: Sadri
keywords: Differential Scanning Calorimetry; Instrumentation; Nickel-Titanium; Root Canal Preparation; Scanning Electron Microscopy; Transition Temperatures; X-ray Diffraction