[Indication of osteoprotegerin (OPG) and receptor activator of nuclear factor kappa B ligand (RANKL) in gingival crevicular fluid to remodeling of alveolar bone during retention].

OBJECTIVE: To investigate the level of osteoprotegerin (OPG) and receptor activator of nuclear factor kappa B ligand (RANKL) in gingival crevicular fluid (GCF) during orthodontic retention and corresponding expression of OPG and RANKL in periodontal tissues. METHODS: Fifteen male Wistar rats (age, 6 weeks) were divided into three groups with 5 rats for each. GCF samples were collected at the baseline, 14 days after orthodontic force application, and 14 days after orthodontic force removal. enzyme linked immunosorbent assay (ELISA) was used to quantify the concentration of OPG and sRANKL (soluble receptor activator of nuclear factor kappa B ligand) in GCF. Immunohistochemical staining was performed to identify the OPG and RANKL expression in periodontal tissues. RESULTS: The concentration of sRANKL in GCF increased statistically significant from baseline to T2 (P<0.05) while decreased significantly from T2 to T3 (P<0.05). The concentration of OPG had minimum fluctuation from baseline to T3 without any statistical significance (P>0.05). The sRANKL/OPG ratio in GCF and that in periodontal tissues during the three time points were similar which showed a prominent increase in T2 (P<0.05 and P<0.01, respectively) and sharp decrease in T3 (P<0.05). CONCLUSION: sRANKL/OPG ratio may be one of the predictors reflecting the remodeling of periodontal tissues in orthodontic retention.