Impact of Implant-abutment Connection on Osteoimmunological Parameters in Short Implants: a Randomised Controlled Clinical Trial

The peri-implant crevicular fluid (PICF) contains several inflammatory mediators; the level of these mediators can provide information on the inflammatory state of the tissue, including the activation of mechanisms of bone destruction. In this context, soluble receptor activator of nuclear factor кB ligand (sRANKL) and osteoprotegerin (OPG) have been suggested as molecular determinants of bone resorption. However, currently, there are only limited studies on the molecular responses of healthy peri-implant tissues following placement of implants on function. The null hypothesis of the present study was that there are no significant differences in the levels of sRANKL and OPG in PICF or in the respective levels of six bacterial species or total bacteria levels in submucosal biofilm samples taken from TIF- and TIS-type implants. Therefore, the aim of the present study was to determine the levels of sRANKL and OPG as well as their relative ratio in PICF surrounding the two different types of implant-abutment connections on short implants after a 12-month monitoring period. Additionally, their association with clinical findings and microbiological markers in plaque samples were assessed in the present study.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 one 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 corresponding submucosal biofilm samples using quantitative real-time polymerase chain reaction.