Purushothama, RRakshith, VRSamrat, MRBalaji, DRYalamanchili, SMeghana, K.2025-05-122025-05-122024-08Purushothama R, Rakshith VR, Samrat MR, Balaji DR, Yalamanchili S, Meghana K. . Effect of Two Different Temperatures on Resistance to Cyclic Fatigue of Hyflex EDM TruNatomy and ProTaper Next Files: An In Vitro Study. International Journal of Scientific Study. 2024 Aug; 12(5): 56-602321-63792321-595Xhttps://imsear.searo.who.int/handle/123456789/246964Introduction: One of the important aspects in success of endodontic treatment is root canal instrumentation. Nickel-titanium rotary instruments drastically improved the root canal preparation technique. However, the major disadvantage of these instruments is their unexpected fracture. Intracanal temperature plays an important role in the cyclic fatigue resistance. This study was conducted to compare the effect of two different temperatures on resistance to cyclic fatigue of HyFlex EDM, TruNatomy, and ProTaper Next files. Methods: A total of 30 endobloc and 30 continuous rotary files from each system (n = 10) (GROUP 1: HyFlex EDM, GROUP 2: TruNatomy, GROUP 3: ProTaper Next) were used for the study. Samples were further divided into two subgroups (n = 5) and tested at room temperature and at stimulated intracanal temperature (45–50°C). A digital thermometer was used to measure the temperature of the water. The number of cycles to fracture was calculated. Length of fractured segments was measured using a digital caliper. The fractured files were examined under a scanning electron microscope to determine morphological characteristics. Data were analyzed using I Kruskal–Wallis test, post hoc Mann–Whitney test, and Wilcoxon sign test. Results: At both temperatures, HyFlex EDM files showed the highest number of cycles to fracture compared with ProTaper Next and TruNatomy files (P < 0.05). There was no significant difference in fractured segment length at intracanal stimulated temperature whereas TruNatomy showed higher fracture segment length at room temperature. Conclusion: Within the limitations of this in vitro study, it can be concluded that HyFlex EDM showed the highest cyclic fatigue resistance both in the room and stimulated intracanal temperature compared to TruNatomy and ProTaper Next. There was increase length of fracture segment of TruNatomy at room temperature. Scanning electron microscope analysis showed the presence of morphological changes in the fractured files.Cyclic fatigueHyFlex EDMProTaper NextTemperatureTruNatomyJournal ArticleIndiaProfessor, Department Conservative Dentistry and Endodontics, Sharavathi Dental College and Hospital, Shivamogga, Karnataka, IndiaSenior Lecturer, Department Conservative Dentistry and Endodontics, Subbaiah Institute of Dental Sciences Shivamogga, Karnataka, IndiaProfessor and HOD, Department Conservative Dentistry and Endodontics, Sharavathi Dental College and Hospital, Shivamogga, Karnataka, IndiaSenior Lecturer, Department Conservative Dentistry and Endodontics, Sharavathi Dental College and Hospital, Shivamogga, Karnataka, IndiaSenior Lecturer, Department Conservative Dentistry and Endodontics, Sharavathi Dental College and Hospital, Shivamogga, Karnataka, India3rd Year Post Graduate Student, Department Conservative Dentistry and Endodontics, Sharavathi Dental College and Hospital, Shivamogga, Karnataka, India