Objective:To investigate the effects of bracket-free invisible orthodontic technique versus traditional fixed orthodontic technique on the levels of inflammatory factors in the gingival crevicular fluid of orthodontic adolescents. Methods:A total of 67 orthodontic patients who received their first orthodontic treatment in Huzhou Central Hospital from June to September 2020 were included in this study. They were randomly divided into an observation group ( n = 34) and a control group ( n = 33). The control group was treated with traditional fixed orthodontic treatment. The observation group was treated with invisible orthodontic treatment without brackets. At 0, 1, 2, 4, and 6 months of treatment, the level of inflammatory factors and periodontal index were compared. Results:At 0 and 1 month of treatment, there were no significant differences in the levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in the gingival crevicular fluid between the observation and control groups (all P > 0.05). At 2, 4, and 6 months of treatment, the levels of IL-1β, IL-6, and TNF-α in the observation group were significantly lower than those in the control group (IL-1β: t2 months = 5.56, P = 0.042; t4 months = 8.14, P = 0.019; t6 months = 9.87, P = 0.002. IL-6: t2 months = 7.15, P = 0.029; t4 months = 7.94, P = 0.021; t6 months = 9.16, P = 0.007. TNF-α: t2 months = 6.87, P = 0.039; t4 months = 7.65, P = 0.026: t6 months = 9.89, P = 0.001). In each group, gingival index (GI), sulcus bleeding index (SBI), probing depth (PD), and plaque index (PLI) increased significantly after treatment. At 0 and 1 month of treatment, there were no significant differences in GI, SBI, PD, and PLI between the two groups (all P > 0.05). At 2, 4, and 6 months of treatment, GI, SBI, PD, and PLI in the observation group were significantly lower than those in the control group (GI: t2 months = 3.62, P = 0.073; t4 months = 8.16, P = 0.018; t6 months = 8.54, P = 0.016. SBI: t2 months = 5.65, P = 0.042; t4 months = 7.56, P = 0.027; t6 months = 8.15, P = 0.019. PD: t2 months = 5.652, P = 0.042; t4 months = 7.56, P = 0.027, t6 months = 8.15, P = 0.019. PLI: t2 months = 9.57, P = 0.006; t4 months = 9.98, P = 0.002. t6 months = 9.94, P = 0.010). In addition, at 1 month of treatment, PLI in the observation group was significantly lower than that in the control group ( t = 9.99, P = 0.001). Conclusion:Bracket-free invisible orthodontic treatment provides better protection on periodontal tissue and has less impact on periodontal health than traditional fixed orthodontic treatment.