Internal hexagon
Also known as: Internal hex, Internal hexagonal connection
An implant-abutment connection in which the hexagonal anti-rotation feature sits inside the implant body, so the abutment drops into a recess below the platform rather than over a boss above it.
Key facts
| Connection category | Internal connection. A 2020 review lists internal hexagons alongside internal octagons and Morse taper designs as the subdivisions of the internal connection family.Verified spec[1] |
|---|---|
| Anti-rotation feature | A hexagonal recess machined into the implant body below the platform.Verified spec[1] |
| Clinical evidence | A 2020 review reported that internal connections exhibited a lower microgap than external hexagons and generally maintained higher preload values. A 2017 systematic review found internal hexagonal designs performed better than external variants but still showed moderate microleakage, with conical designs sealing better than either.Verified spec[1][2] |
| Taper angle | Insufficient evidence(A pure internal hexagon is a flat-seated joint, but many implants marketed as "internal hex" combine a hexagon with a conical seat above it. The angle, where one exists, is specific to the product and not to the category.) |
| Geographic availability | The internal hexagon is used very widely across the mid-market and by most manufacturers producing components compatible with other systems. Because it is so common, a quotation that names only "internal hex" identifies almost nothing about which implant was used. |
| Platform switching | Independent of the hexagon itself. Many internal hex implants are supplied with platform-switched abutments and many are not; the two design choices are made separately. |
Overview
Moving the hexagon inside the implant did two useful things at once. It lengthened the engagement between implant and abutment, so the joint resists sideways load along a longer wall rather than at a short boss, and it moved the interface down inside the fixture, away from the crestal bone. The comparative literature bears out the mechanical part: less screw loosening, smaller microgaps than external hexagons, though not as small as a properly conical joint. The category is also where the terminology gets slippery. A great many implants sold as "internal hex" are actually hybrids, with a conical seating surface doing the sealing and the hexagon serving only to index the abutment into one of six positions. That is a materially different joint from a flat-seated hexagon, and the label does not distinguish between them. It is also the connection most often copied by third-party component manufacturers, which is why compatibility claims cluster around it - and why the fit of a compatible part is a real question rather than a theoretical one.
Sources
Numbers match the citations beside each claim above.
Clinical evidence
- [1]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.
- [2]Microleakage at the Different Implant Abutment Interface: A Systematic Review — Journal of Clinical and Diagnostic Research, via PubMed Central, 2017. Accessed 2026-07-21.