Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 19 0 2022 07 02 3916 3916 Eilnaz Ehrami Department of orthodontics, School of Dentistry, Isfahan (Khorasgan) Branch ,Islamic Azad University, Isfahan, Iran Alireza Omrani Department of orthodontics, School of Dentistry, Isfahan (Khorasgan) Branch ,Islamic Azad University, Isfahan, Iran Masood Feizbakhsh Department of orthodontics, School of Dentistry, Isfahan (Khorasgan) Branch ,Islamic Azad University, Isfahan, Iran 2021 01 07 2021 12 11 Objectives: This study compared the effects of fluoride mouthwashes on surface topography of orthodontic wires, and static and kinetic frictional forces between the stainless steel (SS) orthodontic brackets and SS and nickel-titanium (NiTi) archwires. Materials and Methods: This in vitro, study evaluated 240 standard SS maxillary central incisor brackets and 0.018, and 0.025×0.019 inch NiTi and SS archwires. The wire-bracket sets (different combinations of wire diameters and types) were exposed to artificial saliva (control), 0.05% sodium fluoride (NaF) for 1 minute daily, or 0.2% NaF for 1 minute, weekly (37°C) for 3 months. The wires were pulled in bracket slots by 5 mm in a universal testing machine (10 mm/minute). The static and kinetic forces were measured. The surface topography of wires was inspected under a scanning electron microscope (SEM; x500). Data were analyzed by SPSS 25. Results: The mean static and kinetic frictional forces of 0.025×0.019 inch NiTi wire in 0.05% NaF group were significantly greater than SS wire (P=0.000). The mean kinetic frictional force in 0.05% NaF was significantly greater than 0.2% NaF and artificial saliva for all wires (P=0.001). The mean static and kinetic forces in 0.2% NaF were significantly greater than in artificial saliva (P=0.025). In all groups, larger wires showed higher mean frictional forces (P=0.000). SEM results revealed higher wire surface roughness in 0.05% NaF followed by 0.2% NaF group. Conclusion: Weekly use of 0.2% NaF mouthwash is recommended during sliding mechanics to minimize frictional forces between the SS and NiTi wires and SS brackets. https://fid.tums.ac.ir/index.php/fid/article/view/3916