Comparison of Four Rotary NiTi Files on Vertical Root Fracture Resistance of Endodontically Treated Teeth: An In-vitro Study

Introduction: There are several reasons associated with vertical root fracture, from which biomechanical preparation can be considered as one of the predisposing factors which can increase the susceptibility to vertical root fracture. It depends upon the amount of forces used during the preparation and taper of the file systems used for the preparation. Aim: To compare vertical root fracture resistance of teeth prepared by four different rotary NiTi file systems. Materials and Methods: This was an in-vitro study conducted on 150 extracted mandibular premolars from September 2022 to November 2022. All the teeth were decoronated keeping the remaining root length of 13 mm. The roots were divided into five groups of 30 each. Group-1: Vortex blue, Group-2: Edge File X7, Group-3: Hyflex EDM, Group-4: ProTaper Gold, Group-5: Control Group. The roots were placed in silicon impression material to resemble periodontal ligament. All the root canals were negotiated to their terminus with stainless steel K Files except the control group. All teeth from each group were then prepared with their respective file systems and were obturated and sealed with composite. All the samples were then tested with a universal testing machine to evaluate the vertical root fracture. Compressive force was applied and the load necessary to fracture was recorded in newtons. Statistical analysis was done using one-way Analysis of Variance(ANOVA) followed by post-hoc Tukey test. Results: Fracture resistance of Group-5 (Control group) was the highest (522.789 +/- 98.79215), followed by Group-1 (Vortex blue) (457.964 +/- 37.75982) whereas Group-4 (ProTaper Gold) showed least resistance (349.445 +/- 33.62643). The fracture resistance of Vortex blue file system showed significant difference when compared to Hyflex EDM and ProTaper Gold file systems (p<0.001). Conclusion: The maximum amount of force needed to fracture the samples were prepared with vortex blue file while ProTaper Gold file shows minimum amount of force needed to fracture the sample.