Sending digital impressions to a lab without rework comes down to three things arriving intact: a complete scan, an unambiguous prescription, and a file the laboratory can open without conversion. When any one of them fails, the case returns as a question, a re-scan or a remake, and the chairside time you saved by scanning disappears in the follow-up. Most rework in digital dentistry is not a technology failure. It is a handover failure, and handovers are fixable with a short checklist and a shared naming convention. This guide covers how to prepare the scan, how to transfer it reliably, what the prescription must contain, and how clinics and laboratories can agree a protocol that both sides actually follow.
What Sending Digital Impressions to a Lab Actually Requires
Digital impressions are not photographs; they are measurement datasets with strict requirements. The laboratory needs closed surfaces at every margin, sufficient occlusal and buccal coverage for design, an opposing arch in occlusion, and a bite registration that ties the two together. If any of those is missing, the technician either guesses or asks you to re-scan.
The good news is that modern scanning hardware makes the capture step fast. The AI-30 records a full arch at ≥30 fps in under 60 seconds in most cases, and the AI-50 captures at 38+ fps with ≤7 μm single-tooth accuracy for implant and multi-unit work. Both scan powder-free in true colour and export STL, PLY and OBJ, which means the laboratory can open the case in exocad, 3Shape or its own pipeline without a proprietary viewer.
The Three Stages Where Rework Originates
Rework clusters at three points, and distinguishing them is the first step toward reducing it. Scanning failures are missing data: a hole under a contact point, a margin cut off by the gingiva, or a scan that jumps because the tip lost tracking. Design failures happen at the laboratory: a margin line drawn on an ambiguous surface, an occlusion left unadjusted, or a connector placed where the scan gave no information. Communication failures are the quietest: the wrong shade, an unstated material preference, a delivery date nobody confirmed.
Only the first stage is a clinical problem. The second is a data problem the laboratory can often catch if the intake check is disciplined. The third is an agreement problem, and it costs the most per incident because the case has already been manufactured when the mismatch surfaces.
Preparing the Scan When Sending Digital Impressions to a Lab
Preparation takes about ninety seconds and prevents most returns, even on a busy morning with a full book and a nervous patient in the chair. Retract the soft tissue so the finish line is visible around the full circumference, and dry the field before capture. Scan beyond the margin rather than stopping at it, because the technician needs supragingival data to design the emergence profile. Capture the opposing arch in full, including the distal surfaces that will contact the restoration.
Then check the scan on screen before you send it. Rotate the model and look for holes, floating fragments and smeared areas. Use the software's edge detection and AI-assisted filling to close small gaps, but re-scan rather than patch anything near a margin. A filled margin is a guess, and a guess at the margin is a remake.
Digital Impression Transfer: File Format, Naming and Compression
Format decisions cause a surprising number of delays. STL is universally accepted for surfaces; PLY and OBJ carry colour, which helps with shade communication but is not supported by every laboratory system. Ask which formats your laboratory accepts and standardise on the intersection rather than on the union. If the laboratory needs colour for shade matching, send one coloured PLY alongside the STL rather than substituting it.
Naming matters as much as format. A file called scan1.stl tells the technician nothing and is the most common cause of two cases being swapped. Adopt a convention that encodes patient identifier, tooth number, date and stage, for example a prefix plus tooth plus date, and apply it in the scanning software so nobody has to rename files by hand. Compression is the last technical point: transfer large datasets in a zip archive rather than truncating quality, because a compressed mesh with lost vertices is not a smaller version of the scan, it is a different scan.
Lab Communication Workflow: What the Prescription Must Contain
A prescription that travels with the file prevents most questions. Six items cover the majority of cases.
- Restoration type and material: crown, bridge, onlay, guide or model, with the material class the clinician intends.
- Tooth numbers and units: written in the numbering system the laboratory uses, with the span stated explicitly.
- Margin design and cement space: any deviation from the laboratory's default, stated rather than assumed.
- Shade and characterisation: shade reference, plus photographs where the case is aesthetic.
- Occlusal scheme: which contacts to preserve, and whether the case is a conformative or reorganised approach.
- Delivery date and shipping route: when the clinician needs it in hand, not when it should be dispatched.
Attach the prescription to the case in the same transfer rather than sending it by a separate message, because the two items get separated precisely when the case is urgent.
Rework Causes by Stage
The table groups the common causes by stage and pairs each with the control that removes it. Clinics and laboratories that review this table together usually find two or three controls they can adopt immediately.
| Stage | Typical cause | What the laboratory sees | Control |
|---|---|---|---|
| Scan | Margin obscured by soft tissue | Margin line ambiguous, design guesswork | Retraction and drying before capture |
| Scan | Missing distal or occlusal data | Hole in the model, contact points unusable | Scan past the margin and beyond the contacts |
| Scan | Impression or model not scanned fully | Incomplete die, unusable for design | Full-arch capture in one pass, check on screen |
| Transfer | Proprietary format or renamed file | Case cannot be opened or is misidentified | Open STL export plus agreed naming convention |
| Communication | Shade or material unstated | Remake after manufacturing | Six-item prescription attached to the case |
| Communication | Delivery date assumed | Rush fee or missed appointment | Date in hand stated on the prescription |
Case Submission Scan Checklist
Run this list before every submission. It takes less time than a single phone call about a remake.
- Finish line visible around the full circumference, with no bleeding obscuring the margin.
- Scan extends past the margin onto adjacent supragingival surfaces.
- Opposing arch captured in full, including the distal surfaces.
- Bite registration recorded and verified against the two arches.
- Model checked on screen for holes, floaters and smeared regions.
- Implant cases include the scan body position with the correct library selected.
- File exported in the agreed format, named to the convention, zipped if large.
- Prescription with all six items attached to the same transfer.
Laboratories can support this by publishing their own intake requirements, including accepted formats, numbering system and the design defaults they apply when nothing is stated. A one-page intake sheet removes most ambiguity and costs nothing to maintain.
Frequently asked questions
Do I need to send photographs with a digital impression?
For aesthetic cases, yes. Colour data in a PLY file helps, but a photograph of the prepared tooth and the adjacent teeth gives the technician information that geometry cannot carry, particularly for incisal characterisation.
What should I do if the scanner loses tracking mid-arch?
Stop, return to a known landmark and re-capture the segment rather than allowing the software to stitch a guess. Stitching errors are hard to see on screen and produce contacts that do not match the mouth.
Is a printed model still needed for every case?
No. Many restorations are designed and produced digitally, and a model is printed only when the workflow requires a physical reference, for example for a try-in or a framework fit check. Ask the laboratory which cases need one.
How can a clinic and laboratory agree a protocol quickly?
Use one page: accepted formats, naming convention, prescription fields and delivery expectations. Review it after the first twenty cases and adjust the two items that caused the most questions.
Want a handover protocol that eliminates most returns? contact our team and we will share a clinic-to-laboratory intake template covering formats, naming and prescription fields. Explore the digital dentistry workflow solutions for the full scan-to-print chain, review the intraoral scanner range for capture performance, and check the dental laboratory scanner options if your laboratory also digitises physical impressions.
