Objective: To analyze the types of connections that are external, internal and Morse cone, and evaluate their biomechanics, the impact they have on the alveolar bone and microbial contamination.

Methodology: PubMed, SCOPUS and Google Scholar databases were reviwed to find recent articles published on implant-abutment connections with the following keywords "implant-abutment connection", "fixture-abutment connection", "implant-abutment interface", "External hexagon", "internal hexagon", "internal connection", "conometric connection".

Results: The external connection presents micromovement under lateral load and this can create a microgap at the implant-adhesive interface, causing future bone loss and bacterial accumulation inside the implant. As for the internal connection, it was found that it presents a smaller microgap, managing to maintain the crestal bone for a longer time and having a minimum bacterial proliferation inside the implant. The conical connection systems seem to have almost no microgap and therefore tend to have better adaptation and longevity of the peri-implant hard and soft tissues, in addition to a non-significant bacterial microleakage. It was found that the biomechanics of each type of connection are closely related to peri-implant bone loss and this is mainly developed by microbial contamination.

Conclusion: Further in vivo studies are needed to confirm which connection offers a better prognosis and longevity of the implant treatment performed.