ABSTRACT
Context: Preparation of the root canal system is recognized as being one of the most important stages in root canal treatment which removes organic debris and microorganisms from the root canal system by means of chemico- mechanical preparation and irrigation of the canals. The use of nickel-titanium instruments has drastically reduced the time and the difficulties that were encountered with traditional hand instruments made up of stainless steel. Utilizing properties of super-elasticity, shape memory and different tapers of these instruments reduces not only the possibility of canal transportation but also affects both the geometry and volume of root canals. This subjects the root dentin to stress and consequently dentinal defects which increases the risk of root fracture during or after root canal treatment. Clinicians now have the opportunity to choose from differently tapered instruments having unique characteristics in their geometry and metallurgy. These are progressively tapered instruments, fixed tapered instruments, and variable tapered instruments, which come with the benefit of conforming to the root canal anatomy as well as removing dentin as little as possible while cleaning and shaping. The aim of this study was to examine the influence of instrument taperAim: on the fracture resistance of endodontically treated roots under in vitro experimental conditions.Conclusion: Under the limitations of this study in in-vitro conditions there were no significant differences between the fracture loads between the different file systems used, however samples prepared with Hyflex EDM recorded the highest fracture resistance, followed by ProTaper NEXT, ProTaper Gold and NeoEndo Flex respectively.