title: Impact of implant-abutment connection on osteoimmunological and microbiological parameters in short implants: a randomized controlled clinical trial.
abstract: OBJECTIVE
  The study aimed to determine the levels of soluble receptor activator of nuclear factor-кB ligand (sRANKL) and osteoprotegerin (OPG) as well as their relative calculated ratio in peri-implant crevicular fluid (PICF) obtained around two different types of implant-abutment connection on short implants following a 12-month monitoring period. Moreover, the levels of a number of oral bacterial species were investigated in the corresponding submucosal biofilm samples.
  
  
  METHODS
  Thirty short implants were randomly placed in posterior maxillary edentulous sites using a split-mouth design in 15 periodontally healthy subjects. Tapered interference fit (TIF) and taper-integrated screwed-in (TIS) types of implant-abutment connections were selected for investigation. PICF and submucosal biofilm samples were collected 1 month after surgery and repeated 12 months after prosthetic loading. Clinical parameters, including probing depth, dichotomous presence of bleeding on probing, and plaque index, were recorded and digital periapical radiographs were taken at each time point. sRANKL and OPG levels in PICF were analyzed using an enzyme-linked immunosorbent assay. Total bacterial levels, as well as levels of Fusobacterium nucleatum, Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia, Prevotella intermedia, and Streptococcus oralis, were analyzed in the corresponding submucosal biofilm samples using quantitative real-time polymerase chain reaction.
  
  
  RESULTS
  The total amount of sRANKL in TIF implants was 2.64-fold lower than that in TIS implants at baseline (P < 0.001), whereas similar levels were found after 12 months (P > 0.05). Accordingly, OPG and RANKL/OPG ratio were similar between the groups at each time point (P > 0.05). Microbiological results were similar in both groups at each time point (P > 0.05).
  
  
  CONCLUSIONS
  The results of this longitudinal study suggested that sRANKL and OPG in PICF, as well as microbiological parameters in submucosal biofilms, were similar between TIF and TIS implants, after a 12-month monitoring period, despite early differences in the former. Therefore, the type of implant-abutment connection does not appear to influence longitudinally the levels of osteoimmunological and microbiological markers in the peri-implant tissues of short implants.
authors.affiliation: Department of Periodontology, School of Dentistry, Adnan Menderes University, Aydın, Turkey.
authors.forename: Veli Özgen
authors.initials: VÖ
authors.lastname: Öztürk
authors.affiliation: Department of Periodontology, School of Dentistry, Ege University, Izmir, Turkey.
authors.forename: Gülnur
authors.initials: G
authors.lastname: Emingil
authors.affiliation: Department of Dental Medicine, Karolinska Institute, Stockholm, Sweden.|Division of Oral Microbiology and Immunology, Institute of Oral Biology, Center of Dental Medicine, University of Zürich, Zürich, Switzerland.
authors.forename: Nagihan
authors.initials: N
authors.lastname: Bostanci
authors.affiliation: Department of Dental Medicine, Karolinska Institute, Stockholm, Sweden.|Division of Oral Microbiology and Immunology, Institute of Oral Biology, Center of Dental Medicine, University of Zürich, Zürich, Switzerland.
authors.forename: Georgios N
authors.initials: GN
authors.lastname: Belibasakis
mesh_terms: D000328:Adult; D001419:Bacteria / Q000302:isolation & purification*; D018441:Biofilms; D059605:Dental Implant-Abutment Design; D017267:Dental Prosthesis Design; D005260:Female; D005883:Gingival Crevicular Fluid / Q000737:chemistry*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009061:Mouth Mucosa / Q000382:microbiology*; D053244:Osteoprotegerin / Q000032:analysis*; D011446:Prospective Studies; D053245:RANK Ligand / Q000032:analysis*
chemical_list: D053244:Osteoprotegerin; D053245:RANK Ligand; C506030:TNFRSF11B protein, human; C505688:TNFSF11 protein, human
keywords: OPG; RANKL; implant-abutment connection; peri-implant crevicular fluid; short implant; submucosal biofilm