Objective: Glide path preparation has been recommended as a mandatory clinical step to ensure the safe usage of nickel-titanium (NiTi) rotary instruments. This study aimed to evaluate the incidence of fracture of ScoutRace, ProGlider and One G files when used to mechanically negotiate curved canals. Materials and methods: Seven files from each brand were used to mechanically negotiate mesial canals of extracted human mandibular molars with root canal curvature angle ranging from 25 to 40 degrees. All rotary files were used until fracture occurred. The number of canals that were prepared and the total active instrumentation time for each file till fracture were recorded. Data were scored and statistically analysed using Kruskal-Wallis and Mann-Whitney tests (P ≤ 0.05). Results: One G had a significantly higher number of negotiated canals till fracture when compared with ScoutRace (P 0.05), and no significant difference when compared with ProGlider (P > 0.05). The difference between ScoutRace and ProGlider was not significant (P > 0.05). ScoutRace recorded the highest incidence of fracture, followed by ProGlider and One G. There was a statistically significant difference between ScoutRace and ProGlider (P 0.05), as well as between ScoutRace and One G (P 0.05) regarding their total active instrumentation time till fracture, whereas there was no significant difference between ProGlider and One G (P > 0.05). Conclusions: Under the limitations of this study, the One G file appeared to be suitable for safe and efficient glide path establishment, followed by ProGlider and ScoutRace files. Schlagwörter: fracture incidence, mechanical glide path, One G, ProGlider, ScoutRace