title: Soluble RANKL in crevicular fluid of dental implants: a pilot study.
abstract: BACKGROUND
  Receptor activator of NF-kappaB ligand (RANKL), a member of the tumor necrosis factor superfamily, is a key mediator of osteoclast formation, activation, and survival. Thus, it is reasonable to hypothesize that there might be a functional relationship between RANKL expression and peri-implantitis.
  
  
  OBJECTIVE
  This pilot study was performed to determine the reference levels for soluble RANKL (sRANKL) in peri-implant crevicular fluid and to correlate them with the clinical parameters associated with inflammatory reactions and bone destruction.
  
  
  METHODS
  The clinical parameters probing depth (PD), modified bleeding index (MBI), and modified plaque index (MPI) served as indicators for bone resorption and inflammation. Exclusion criteria for calculations were the detection limit of the immunoassay and the minimum acceptable crevicular volume for measurement. From the 84 collected samples of 16 patients, 30-84 years of age, with a total of 19 implants, 29 met these criteria. The absolute amount of sRANKL within crevicular fluid adsorbed to filter strips was a median of 0.18 femtomol (fmol; range, 0.08-0.53) and 0.26 nM (range, 0.09-1.21) when normalized by volume. PD was 4 mm in median and varied within a range between 2 and 12 mm.
  
  
  RESULTS
  Absolute amounts of sRANKL showed no correlation with the adsorbed volume and the clinical parameters PD, MBI, and MPI. When sRANKL was normalized by volume, no correlation with the clinical parameters PD, MBI, and MPI was observed either. The patients' age was not associated with total sRANKL and the concentration of RANKL within crevicular fluid. Absolute levels of sRANKL and sRANKL concentration did not show any differences based on the sampling sites buccal and lingual, or on the patients' gender. A significant difference in sRANKL concentration was detectable when samples from maxillary implants (0.31 nM median; range, 0.12-1.21) were compared with samples from mandibular implants (0.21 nM median; range, 0.09-0.6) (p=.03). Absolute levels of sRANKL were not different between the maxilla and the mandible.
  
  
  CONCLUSIONS
  Given the limited sample size, our data provide a basis for future prospective longitudinal studies on the possible relevance of sRANKL as a prognostic marker in peri-implantitis, and for an understanding of the pathophysiologic process of the disease as a prerequisite for the design of treatment strategies.
authors.affiliation: Department of Oral Surgery, Vienna Medical University, Vienna, Austria.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Monov
authors.forename: Georg D
authors.initials: GD
authors.lastname: Strbac
authors.forename: Monika
authors.initials: M
authors.lastname: Baron
authors.forename: Barbara
authors.initials: B
authors.lastname: Kandler
authors.forename: Georg
authors.initials: G
authors.lastname: Watzek
authors.forename: Reinhard
authors.initials: R
authors.lastname: Gruber
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016301:Alveolar Bone Loss / Q000145:classification; D015415:Biomarkers / Q000032:analysis; D002352:Carrier Proteins / Q000032:analysis*; D015921:Dental Implants; D003774:Dental Plaque Index; D005260:Female; D005883:Gingival Crevicular Fluid / Q000737:chemistry*; D005884:Gingival Hemorrhage / Q000145:classification; D006801:Humans; D008024:Ligands; D008297:Male; D008562:Membrane Glycoproteins / Q000032:analysis*; D008875:Middle Aged; D010010:Osteoclasts / Q000473:pathology; D010512:Periodontal Index; D010514:Periodontal Pocket / Q000145:classification; D010518:Periodontitis / Q000145:classification; D010865:Pilot Projects; D011379:Prognosis; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018124:Receptors, Tumor Necrosis Factor / Q000032:analysis*; D012995:Solubility; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins / Q000032:analysis*
chemical_list: D015415:Biomarkers; D002352:Carrier Proteins; D015921:Dental Implants; D008024:Ligands; D008562:Membrane Glycoproteins; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018124:Receptors, Tumor Necrosis Factor; C505686:TNFRSF11A protein, human; C505688:TNFSF11 protein, human; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins