RANKL and Osteoprotegerin Levels in Peri-implant Crevicular Fluid From Short Implants

Objectives: The regional microgap between implant/abutment connection can affect the inflammatory state and bone loss of the peri-implant tissues. The peri-implant crevicular fluid (PICF) contains a wealth of information regarding the inflammatory state of the tissue, including the levels of molecular mediators of bone resorption. The aim of this study was to determine levels of soluble receptor activator of nuclear factor-кB ligand (sRANKL) and osteoprotegerin (OPG), as well as their relative ratio in PICF obtained around two different implant/abutment connections on short implants, following a 1-year monitoring period.
Methods: A total 30 short implants placed in 15 periodontal healthy patients at posterior maxilla, collaterally and in a split-mouth design. Tapered interference fit (TIF-Bicon) and taper integrated screwed-in (TIS-Dio) types of implant/abutment connections were used. PICF samples were collected following one month’s healing from the second surgery (without prosthetic loading) and one year after prosthetic loading. Clinical parameters including probing pocket depth, dichotomous presence of bleeding on probing and plaque index were recorded at each time point. Digital periapical radiographs were taken in order to assess bone loss around implants. sRANKL and OPG PICF levels were analyzed by ELISAs. Data were analyzed by non-parametric analysis of variance.
Results: sRANKL PICF levels were significantly higher by 2.64-fold in TIS than TIF types of implants at 1 year (p < 0.001), but this difference was not significant between groups at 1-month (p> 0.05). Accordingly, no differences in OPG PICF levels or sRANKL/OPG ratio were observed between the two implant groups at both periods (p> 0.05). No correlations between sRANKL, OPG or their relative ratio, and clinical parameters or bone loss were detected.
Conclusions: This longitudinal study suggests that the pattern of sRANKL and OPG regulation in PICF is similar between TIF and TIS. Hence this osteo-immunologic response is not influenced by the implant/abutment connection.