الفهرس 
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Abstract
The aim of this study was to compare and evaluate stress distribution on ProTaper NEXT, HyFlex CM and Twisted File in simulated root canals with different radii using Finite Element analysis.
Force applied by operator on rotary files was also measured and used as an input parameter in the analysis.
A biosensor based on EMG was developed for the sake of measuring the operator’s force in vivo. 18 patients were divided into 3 groups (n=6) and each group prepared using different files tested respectively. The same operator performed and the same root selected for modelling was prepared. Connections of the biosensor were according to the muscles responsible for forearm movements during instrumentation.
The results showed no statistical difference between the different files, but still the HyFlex CM file required the highest force followed by the ProTaper NEXT and finally the Twisted file. Mean force was calculated for each file and then used in FEA respectively.
A maxillary molar was selected with 40° curvature of the distobuccal root, working length measured and coronal flaring done using Gates Glidden drills. Tooth was scanned using CBCT; the scan was then transferred to Materialise Mimics for sectioning and revealing of the root canal. CAD programs were finally used for enhancements and adjustments of the model, creating a model with 4mm radius of curvature and another model with radius 2mm radius of curvature.