A crown and a bridge do not require the same information from a scan body
A scan body is not merely a visible marker above the implant. It is a spatial translator between the invisible implant connection and CAD library geometry. For a single crown with an engaging connection, CAD needs not only implant position and axis but also the anti-rotational orientation of the connection. In a bridge on non-engaging Ti-bases, the individual component is rotational and CAD must work with a different degree of freedom around the implant axis.
Official IPD libraries distinguish this logic directly: scan bodies 00 and 02 are defined as engaging for single-unit restorations, while 01 is non-engaging for multi-unit frameworks. The difference is therefore not cosmetic. It is part of the library model of the prosthetic connection.
Mesh, rigid transformation and why “it looks aligned” is not enough
The IOS creates a polygonal mesh of the scan-body surface. CAD then searches for the transformation that best matches the library STL to the scanned object. In simplified form, the spatial transformation can be expressed as pCAD = R · pscan + t, where R represents rotation and t translation.
In an engaging model, R must also preserve the meaning of rotation around the Z-axis because that rotation represents the anti-rotational index of the implant connection. In a non-engaging model, rotation of the individual Ti-base around the axis is handled differently because the component is rotational by design. The library therefore contains not only a “similar STL shape”, but also metadata and prosthetic logic defining how the result should be used.
An incorrect combination of scan body and library branch can therefore produce a convincing on-screen overlay while still giving CAD the wrong interpretation of component orientation. Geometric similarity is not the same as prosthetic equivalence.
IPD TECH provides seven scan-body tolerances from T0 to T6. They help find the best match between the library STL and the real scan, but they do not convert ENG into Non-ENG. Tolerance addresses mesh fit; engaging status addresses the kinematic meaning of the connection.
Why 1 + 1 scan bodies are advantageous for two separate crowns
With two separate implant crowns, each implant represents its own engaging coordinate system. Seating two corresponding scan bodies simultaneously captures their relative position and anti-rotational orientation at the same moment and within the same dataset.
Moving a single scan body from one implant to the other introduces an additional cycle of unscrewing, seating, tightening and a new acquisition state. The anatomy of adjacent teeth may allow the two scans to be registered well, so a sequential approach is not physically impossible. From a repeatability standpoint, however, “1 + 1” removes one unnecessary variable from the chain. This is particularly valuable when diagnosing microrotation or overlay deviations in the tens of micrometres.
- For two separate crowns, use two corresponding engaging scan bodies simultaneously whenever the clinical situation allows.
- For a bridge, explicitly select a non-engaging scan body and the library branch intended for a multiple framework.
- Check not only the scan-body REF, but also the selected CAD kit, implant/MUA level, ENG/Non-ENG status and target Ti-base.
- With ASC, distinguish whether channel direction is constrained by the implant index or can be selected freely through 360° for a rotational restoration.
What “cannot be used” means in precise technical terms
IPD manufacturer resources
IPD TECH Exocad / 3Shape: distinction between engaging 00/02 and non-engaging 01, Scan Abutment Tolerance T0 to T6, and different ASC control for single versus multiple frameworks.
IPD LITE 3Shape: ENG / Non-ENG selection, Tol3 versus Tol5 for the cement gap, and automatically integrated scan-body alignment tolerance T3.
Always work with the current library
Availability of specific variants differs by implant system, platform, working level and CAD-library version.
