Aim: This study aimed to assess the validity of CBCT in the detection of VRF and its orientation in human extracted teeth and to analyze the effect of gutta-percha (GP) endodontic obturation. Finally, to compare different CBCT voxel sizes in VRF diagnosis in both GP obuturated and nonobturated teeth. Materials and Methods: Sixty human teeth were divided into: group I included 30 endodontically treated and GP obturated teeth, group II include 30 endodontically treated but not obturated teeth. Then, VRFs were mechanically induced in all teeth and the teeth were scanned with i-CAT CBCT machine with different voxel sizes of 0.125, 0.2, 0.25 mm. Then, the teeth were inspected by stereomicroscope to confirm the presence of fracture and to detect the orientation of the fractures to act as the gold standard. Result: Different CBCT voxel sizes of 0.125, 0.2 & 0.25mm were found to have the same validity in the VRF diagnosis with 100% sensitivity, 96.4% accuracy and 50% specificity. There was no significant difference between GP obturated and non obturated groups. VRFs occurred mostly in the bucco-lingual direction. Conclusions: VRF detection and its orientation can be accurately assessed by different CBCT voxel sizes imaging, thus using CBCT 0.25 voxel with less radiation dose is preferred. The presence of GP did not hinder the VRF orientation.

Ideally, a nickel-titanium (NiTi) rotary endodontic file should be flexible and resistant to fracture in order to enable a successful non-surgical root canal therapy to either prevent or resolve apical periodontitis through proper cleaning, shaping, disinfection, and sealing of the root canal system [1]. A greater amount of flexibility will enable the file to follow the natural curvatures of the canals closely, incurring less unwanted forces that could result in either apical transportation or legging of the canals [2]. There are two mechanisms which result in a NiTi rotary fracture. These include cyclic fatigue

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