Objectives: To investigate the differences in level of oxidative stress induced by the conventional and self-ligating brackets made of different metallic and aesthetic materials. Material and methods: Concentration of oxidative stress marker 8-hydroxy-2'-deoxyguanosine (8-OHdG) in DNA of murine fibroblast cells L929 was assessed after in vitro exposure to artificial salive of controlled pH 6.75±0.15 in which during the 30 day period brackets were immersed. Three types of conventional (Mini Sprint, Quantum, Inspire Ice) and four types of self-ligating brackets (Speed, QuicKlear, In-Ovation C i Damon 3) were tested. To determine the viability and the changes in number of cells before and after exposure trypane blue dye was used. Results: There was no significant difference in cell viability between metal, ceramic, polymeric brackets and self-ligating brackets made of combination of those materials, but viability was significantly higher compared to positive control (p<0.05). Sapphire ceramic bracket (Inspire Ice) showed high viability, the largest increase in the number of cells and the lowest oxidative stress. A higher concentration of markers of oxidative stress was observed in the full metal brackets (Speed and MiniSprint) and the polyurethane brackets (Quantum) compared to negative control (p<0.05). Conclusion: All types of orthodontic brackets, regardless of the constituent materials are a source of oxidative stress in vitro, but the highest stress induce full metal and polyurethane brackets. Ceramic brackets show the highest degree of biocompatibility compared with polymeric and metal brackets, and those made from combinations of these materials.