Abstract: Objective: The aim of the study was evaluate the effect of orthodontic force in teeth with mild periodontitis by detecting levels of receptor activator of nuclear factor KB ligand (RANKL) and osteoprotegerin (OPG) in gingival crevicular fluid (GCF). Materials and Methods: Select 20 cases without a history of periodontitis patients and 20 patients with mild periodontitis and the inflammation was under control of orthodontic patients. Collect the distal gingival crevicular fluid of the bilateral maxillary teeth after orthodontic force for 0 hour、1 hour、24 hours、7 days、14 days、21 days. Then determinate the concentration of RANKL and OPG in gingival crevicular fluid by ELISA assays. Analyze the change trend of RANKL, OPG and the ratio of RANKL/OPG in the process of orthodontic. Results: In each time point with orthodontic force, there was no significant difference of RANKL and OPG concentration in the gingival crevicular fluid between the two groups (P > 0.05). The ratio of RANKL/OPG in the gingiva crevicular fluid had no difference at every time points (P > 0.05), expect for the 7 days. Use the 0 hour as control, the concentrations of RANKL in gingival crevicular fluid elevated in the two groups at all time points (P < 0.05）,and the highest expression under orthodontic force was at the 7 days. However the concentrations of OPG in gingival crevicular fluid decreased（P < 0.01）, and the lowest expression under orthodontic force was at the 7 days. Furthermore, the RANKL/ OPG Ratios were also increased, and reached maximum at 7 days under orthodontic force. Conclusions: Under the same orthodontic force, the bone reconstructed activities have no obvious distinction with or without periodontitis. Therefore, appropriate orthodontic force does not aggravate the proceeding of the mild periodontitis, and the mild periodontitis is not the absolute contraindication to conventional orthodontics treatment.

Key words: Orthodontics treatment, Mild periodontitis, RANKL, OPG.