Efficacia del sigillo della connessione Morse-taper: studio in vitro con turbidimetria e RT-PCR = Sealing efficacy of Morse-taper implant-abutment connection: an in vitro study using RT-PCR and turbidometry

OBJECTIVESMicroorganisms from the oral cavity may settle at the implant-abutment interface (IAI), thus leading to tissue inflammation around implants.The misfit of the IAI may result in bacterial growth, thus eventually leading to pathology onset like mucositis and peri-implantitis, while the accurate assembly of implant components and the precise fit of the IAI at the level of the bone crest are associated with reduction in the accumulation of inflammatory cells in the peri-implant tissues.Differently from other implant systems, the frictional connection that is typical of Morse-taper design is associated to a very narrow implant-abutment space and a higher functional loading resistance, promoting microbiological sealing in static and dynamic loading conditions.The aim of the present in vitro study was to evaluate bacterial microleakage at the IAI in Morse-taper implant-abutment connections through three different tests validated by existing literature: turbidometry, real-time PCR and horizontal electrophoresis.MATERIALS AND METHODSA bacterial suspension containing a mixture of three bacterial species A. actinomycetemcomitans, F. nucleatum, and P gingivalis was inoculated into the internal cavity of ten implant-abutment samples with a Morse-taper internal connection, except one of the specimens, that was used as negative control.The samples were assembled using a calibrated beater with a standardized force of 15 N, then they were totally immersed individually into culture tubes, obtained mixing agar medium with liquid medium (trypticase soy broth). Finally, they were incubated at 37 degrees C in an anaerobic atmosphere.Turbidity analysis, real-time PCR, and horizontal electrophoresis were performed at 24, 48 and 72 h in order to detect microbial microleakage entity at the implant-abutment connection.RESULTS AND CONCLUSIONSPerformed tests were negative for every specimen, except two of them because of contamination during the manipulation of the components. Morse-taper implants rely on a frictional connection, which results in a very narrow implant-abutment space. This can account for the sealing capability of conical connections against bacterial microleakage.Although in literature no connection type was able to provide a complete bacterial seal at the IAI, Morse-taper connection implants showed less microleakage in comparison with other connection types. Furthermore, this connection type seems to be associated to a lower marginal bone resorption, although it is unclear whether microbiological or mechanical issues are involved.The present in vitro evaluation confirmed the sealing capability of Morse-taper connections in static conditions, in accordance with the results obtained previously in similar published studies.CLINICAL SIGNIFICANCEWhile the technical and mechanical advantages of Morse-tapered implant-abutment connections have been proven extensively in literature, their enhanced sealing capability, which has been proven in this in vitro study through three different validated methods, could prevent microbial colonization of the implant-abutment interface, which is a major clinical concern.Thus, Morse-taper implant connection could be more beneficial to the health of peri-implant tissues. Further evaluations are needed with more samples or in dynamic loading conditions to confirm such conclusions.