Evaluation of stress distribution of mandibular molar TEETH prepared using different rotary file systems

Aim: The aim of this study is to investigate the effect of prepared the resin-containing mandibular first molars with different nickel titanium (Ni-Ti) rotary instruments on the stress distribution using the Finite Element Analysis (FEA) method. Materials and Methods: 3D printed models manufactured were shaped with four different Ni-Ti instruments. The models were divided into five groups: Group 1: ProTaper Gold (PTG), Group 2: Reciproc Blue (RCB), Group 3: Xp-endo Shaper (XPS), Group 4: Hyflex EDM (HEDM), Group 5 : unprepared model. Models were scanned with Scanco Medical Micro-BT 50 (Switzerland) device with 70 kVp power, 114 μA current, 30 µm voxel size, 300 ms integration time, 0.5 mm aluminum filter. Approximately 700-750 cross-sectional images were taken from each sample. Tomography data were saved in DICOM format. Two different loads of 250 N were applied for FEA. First load; applied vertical to the central fossa, second load; applied obliquely to the lingual plane of the buccal tubercle at an angle of 45° to the long axis of the tooth. Stress evaluations were expressed by von Mises Stress, maximum principal stress and minimum principal stress values. Results were evaluated with comments. Results: Stress occurring in both loading conditions is concentrated in the application areas. The highest stress values were observed in Group 3 and the lowest in Group 5. Stresses under oblique loads were observed to be higher than vertical loads. Conclusion: Although volumetric differences cause an increase in stress throughout the part and an increase in stress concentrations in certain regions; It was observed that the stress distributions were similar across. Key Words: Finite element analysis, Microcomputed tomography, Rotary files.