Implant-abutment connection types in dental implant systems

Review

Abstract

It is difficult for clinical dentists to keep up with the rapid development of dental implant systems. The surgical issues of
implantation are mostly clarified, and no surgical revolution is expected in the near future. However, the implant-abutment
connection (IAC) types are permanently being modified. Advantages and disadvantages of the most important
IACs – external hex, tapered hex, external octagon, spline implant, 3-point internal tripod, 6-point internal hex, internal
octagon, 12-point internal hex, Morse taper – are discussed and biological, mechanical and aesthetic aspects of IACs
are detailed in the article. The article can serve as a guide to decide which connection type to use in a certain indication.
Following Brånemark’s protocol, original external hexagonal implants are excellent alternatives for the treatment of anodontous
patients. However, as the indications were broadened, it became necessary to modify the traditional external
hexagon design, and to develop the internal connections. The increased incidence of screw loosening and fracture in
the new indications has been significantly reduced by the modifications and the introduction of internal connections. In
external connections the micro-motion and microleakage are more common between the components, that is why bacterial
seal is less satisfactory. Conical structures provide the best mechanical and biological seal. Conical structures do not
have anti-rotation properties, and therefore the insertion of a polygon or spline into the system is required. The 6-point,
12-point, 3-point internal connections are suitable for this purpose, as are Morse tapers supplemented by hexagonal or
octagonal structures. In the case of angled abutments or single missing tooth is being replaced these structures are recommended.
The force distribution of the internal connections is more favourable for the screw and the implant body, but
it is unfavourable to the bone. In contrast to the external connections, the load on the bone is less, so this must also be
considered when choosing the most suitable type. From the aesthetic point of view, internal connections provide much
better results in terms of the emergence profile, the anatomical accuracy of the replacement, and the potential exposure
of the metal parts.