Abstract: Objective: To investigate the changes of osteoprotegerin (OPG) and receptor activator of nuclear factor kappa B ligand (RANKL) level in perio-implant crevicular fluid (PICF) and to monitor the development of the stability of Straumann^® tissue-level implants by resonance frequency analysis (RFA) during the early phases of healing. Methods: A total of 35 implants (length 10 mm) were placed. PICF samples were collected with filter paper strips at baseline, 1, 2, 3, 4, 6, 8, and 12 weeks post-surgery, respectively. The OPG, RANKL levels were determined by ELISA method. At the same time points, the implant stability quotient (ISQ) values were determined with OsstellTM mentor. Results: During healing, PICF-OPG levels increased significantly 2 weeks after surgery when compared with the 4th-, 6th-, 8th- and 12th-week reevaluation (P<0.05). The OPG/RANKL ratio in PICF was significantly higher (P<0.05) than that in gingival crevicular fluid at 1 week post-surgery. ISQ slightly fluctuated within the first 4 weeks after installation. Following this, the ISQ values increased steadily for all the implants and up to 12 weeks. Significant differences were noted between the mean ISQ values at the 12 th-week and other observation time points. Conclusion: The PICF-OPG levels may be effective in monitoring the process of osseointegration. All the ISQ values indicated the stability of Straumann^®  implants over a 12-week healing period. RFA is a reliable and effective assistant to monitor implant stability.

Key words: Dental implants, Gingival crevicular fluid, Osteoprotegerin, RANK ligand, Resonance frequency analysis