Internal octagon
Also known as: Internal octagonal connection, Octagon connection
An internal connection whose anti-rotation feature is an eight-sided recess inside the implant, used to reposition prosthetic parts in a repeatable orientation.
Key facts
| Connection category | Internal connection. A 2020 review lists internal octagons as one of the three subdivisions of the internal connection family, alongside internal hexagons and Morse tapers.Verified spec[2] |
|---|---|
| Anti-rotation feature | In the best-documented commercial implementation, Straumann’s synOcta connection, an octagon sits below an 8 degree cone and serves "for the repositioning of prosthetic parts".Manufacturer-reported[1] |
| Taper angle | 8 degrees in the Straumann synOcta implementation, where the octagon is combined with a conical seat.Manufacturer-reported[1] |
| Geographic availability | Straumann states that the synOcta connection is available for all Straumann Standard and Standard Plus implants with the Regular Neck and Wide Neck platform.Manufacturer-reported[1] |
| Platform switching | Not inherent to the geometry. Straumann tissue-level implants using this connection address the crestal bone question through the height of the transgingival collar, which lifts the implant-abutment interface away from the bone, rather than through platform switching. |
Overview
The internal octagon is the least common of the three internal anti-rotation geometries, and it is worth understanding why the eight sides exist. An index with more sides gives finer control over where the abutment can be seated - eight positions at 45 degree intervals instead of six at 60 - which matters when an angled abutment has to be aimed at a particular point in the arch. The trade-off is that each flat is smaller, so the geometry is a poorer choice for carrying rotational load on its own. In the implementation that defines the category in practice, Straumann’s synOcta, it does not have to: the load is carried by an 8 degree cone sitting above the octagon, and the octagon is doing indexing rather than mechanics. That division of labour - cone for stability, index for orientation - is the pattern most modern connections follow, whatever shape the index happens to be.
Sources
Numbers match the citations beside each claim above.
Primary sources
- [1]Straumann Dental Implant System — Basic Information (702084/en) — Institut Straumann AG, 2025. Accessed 2026-07-21.
Clinical evidence
- [2]Review of the Mechanical Behavior of Different Implant-Abutment Connections — International Journal of Environmental Research and Public Health, via PubMed Central, 2020. Accessed 2026-07-21.