Purpose To evaluate and compare patients' oxidative stress parameters and antioxidant status with fixed orthodontic appliances during the pubertal and postpubertal growth periods. Methods Saliva samples of 20 pubertal (mean age: 12.94 +/- 0.34 years) and 20 postpubertal (mean age: 16.34 +/- 0.45 years) patients were collected just before the application of fixed orthodontic appliances (T0), 4-5 h (T1), and 7 days (T2) after the initial orthodontic activation. Myeloperoxidase (MPO), nitric oxide (NO), 8-hydroxydeoxyguanosine (8-OHdG) levels, and superoxide dismutase (SOD) activity in the saliva were examined. Repeated measures analysis of variance (ANOVA), least significant difference (LSD) pairwise comparison, and independent sample t-tests were used to analyze the differences between the time points and growth periods, respectively. Results MPO levels in the saliva of patients in the pubertal period showed a significantly higher increase within the first days of treatment (T2-T1) than in patients in the postpubertal period (p < 0.05). The SOD antioxidant enzyme activity decreased in the samples from T0 to T1 in the patients in the pubertal and postpubertal groups and returned to baseline values (T0) at T2 (p < 0.01). No significant differences in the other biochemical parameters between groups were observed. Conclusions Comparing the pubertal and postpubertal groups, orthodontic force application with fixed orthodontic appliances did not change the final levels (on day 7) of antioxidant status or oxidative stress markers, except for MPO in saliva.