Intraoral Scanning Tips That Prevent Remakes

The scan looked complete on the cart screen. Then the lab calls: the distal margin fades into tissue, there is a hole where the mesial contact should be, or the bite lines up on one side only. The case waits for a rescan, or the crown comes back needing adjustment.

Many of these problems can be seen on screen before you press Send. Below: the scanning errors behind remakes, what the lab sees, and how to avoid each one, from accuracy research and the scanner makers' own guidance.

Quick Answer

Scanning errors behind remakes, such as a margin hidden by tissue or moisture, holes at the prep or contacts, a one-sided bite and stitching errors, can be caught at the chair. Retract and dry before scanning the prep, follow your scanner's recommended path, use a half-arch scan for single crowns unless more than one tooth is missing, capture full adjacent teeth and a bilateral bite, and check the screen before sending.

What Does the Lab See When a Scan Goes Wrong?

How Do You Keep the Margin Visible and Dry?

A 2025 review of factors affecting scans for tooth-supported restorations found that intracrevicular finish lines give lower accuracy than equigingival or supragingival ones, and that simpler preparations with a larger total occlusal convergence scan more accurately. A 2023 meta-analysis of 15 in vitro studies found accuracy significantly better under dry conditions.

Align's iTero guide recommends a double-cord technique with one cord left in the sulcus during scanning. 3Shape tells TRIOS users to dry the teeth well, and if saliva distorts an area, to dry it and rescan.

Scan the prep while it is open and dry

The iTero protocol scans the opposing arch first, then the prep: dry it, start with an occlusal view to see the margin, roll from lingual to buccal and from distal to mesial, and fill significant voids immediately. If you cannot expose and dry a margin at all, a scan is the wrong record for that tooth; see Digital vs. Conventional Impressions.

Does the Scanning Path Matter?

A scanner builds the model by joining overlapping images (image registration, in Dentsply Sirona's words). Each manufacturer publishes its own path:

In a 2025 lab study of 225 Primescan scans with nine strategies, a continuous linear path over the full jaw, which the authors note matches the manufacturer's recommendation, and a combined pattern were more accurate than a zig-zag motion, and linear full- or half-jaw paths were truer than scanning sextant by sextant.

A 2025 meta-analysis of TRIOS 3, TRIOS 4, iTero, Primescan and Medit i500 found that only TRIOS 3 lost accuracy at longer distances and faster speeds; the authors advise 5 to 10 mm and slower movement for it.

Full Arch or Half Arch: Which Is More Accurate?

Shorter scans tend to be more accurate: a 2018 systematic review of 32 studies concluded that reducing the scan span improves accuracy. A 2025 lab study of TRIOS 5, Primescan, i700 and iTero, with a crown prep on a first molar, found half-arch scans most accurate at the prep, the margin and the adjacent tooth, and complete-arch scans started in the opposite quadrant least accurate.

In a 2026 clinical study, complete-arch scans from six current scanners showed trueness of 41 to 96 µm, and precision ranged from 21 µm for a high-precision impression to 82 µm for the least precise scanner. The authors concluded that high-precision impressions remain the standard for dentate complete arches.

When to scan the whole arch

A 2024 decision guide recommends a reduced scan extension for crowns and short-span bridges when no more than one tooth is missing in the scanned part of the arch, and complete-arch scans otherwise. For a complete arch, the 2025 factors review advises starting in the quadrant of the preparation. The bite has its own rules; see Why Crowns Come Back High or With Open Contacts.

How Do You Capture Adjacent Teeth and Contacts?

The lab sets each contact against the neighbor surface in the file. Primescan's instructions add a separate approximal scan of the prep in the distal and mesial directions; the iTero guide angles or rotates the wand tip to capture the contacts. The 2025 review found that more space between a prep and the adjacent tooth gives better accuracy, and that existing restorations on the prep and neighbors reduce it.

How Should You Scan the Opposing Arch and the Bite?

For one prep, Align's guide says a full opposing arch is not necessary; capture the opposing teeth over the prep and enough of the arch to seat the bite. Medit recommends enough gingiva on both arches, or the occlusion is difficult to align. Primescan's instructions call for a buccal bite scan near the prep with teeth of both jaws and 5 mm of gingiva, on both sides for a full jaw. 3Shape asks TRIOS users to scan 3 to 4 teeth even if the scans snap together earlier, and suggests a cotton roll in the gap when many teeth are missing; tell the lab if you used one.

How Do You Spot Stitching Errors Before You Send?

3Shape describes two common errors. A ghost image appears when the scanner moves too abruptly and adds images in the wrong place, creating a "new tooth". A stitching error occurs when the scan strategy is not followed and data are missing. For both: trim the area, resume on a previously scanned tooth and move slowly into the gap; if the error is too big, start over. For a registration error, Dentsply Sirona advises returning to an area already acquired, ideally occlusal.

In a TRIOS 3 study, rescanning three 12 mm holes in one quadrant reduced trueness and precision, and the authors call for scans without mesh holes.

Check the prep, not only the mesh

Align's prep review checklist: the margin is clearly visible, the prep is fully captured, nothing such as overlapping tissue obstructs the margin, and the bite is in centric occlusion. Its Occlusal Clearance Tool shows whether the prep has enough reduction for the material in the Rx, so you can reduce and rescan only that area. Reduction targets are in our Crown Prep Guide.

Implant scans follow the same rules, plus a scan body that matches a library file and is fully seated; see How to Scan Implants.

Does Operator Experience Matter?

Less for accuracy than for time. A 2026 meta-analysis from the American Academy of Fixed Prosthodontics found inexperienced operators had trueness lower by only 2.51 µm and took about 41 seconds longer. After training, trueness improved by 19.22 µm and scanning time fell by about 76 seconds. Certainty was low, but whoever scans in your office benefits from training on that scanner.

What Should the Rx and Notes Say?

Beyond material and shade (see How to Fill Out a Dental Lab Rx), add what the scan cannot show:

• Margins: where a finish line is subgingival and how you retracted it.
• Pre-op scan: iTero, for example, offers a pre-treatment scan so the lab can copy the original anatomy.
• Bite: anything unusual, such as a cotton roll in a gap.
• Contacts and reduction: your contact preference, and any spot you know is tight.

Connection steps by scanner are in How to Send a Scan to a Dental Lab; causes beyond scanning are in Crown Remakes: What Really Causes Them.

Digital Cases at Elegant Dental Laboratory

• Digital scans are reviewed before production, and every case is made in house in Brooklyn by more than 35 technicians.
• We accept STL and PLY files from all major intraoral scanners, with direct connections for iTero, 3Shape TRIOS, Dentsply Sirona, Medit, Carestream, Planmeca, Shining 3D, ORI and Panda (setup steps).
• Zirconia, IPS e.max and implant restorations; scan bodies are available to practices.
• 5 business day standard turnaround on most restorative cases, rush options, and up to a 7-year warranty on final restorations (policies and warranties). Call 877-335-5221.

FAQ

Is a half-arch scan enough for a single crown?

Usually, if no more than one tooth is missing in the scanned area. In lab testing, half-arch scans were the most accurate at the prep.

Should I start a full-arch scan on the side of the prep?

Yes. Complete-arch scans started in the opposite quadrant gave the least accurate prep in a 2025 lab study.

Should I rescan a hole or redo the whole scan?

Rescan small holes from captured data; for a large error, such as a ghost tooth, start over.

Does it matter whether the dentist or the assistant scans?

Experience made only a small difference in accuracy; training improved accuracy and speed.

How fast should I move the scanner?

Slowly and close. TRIOS 3 lost accuracy at greater distances and speeds; Primescan's ideal distance is 2 mm.

Reviewed by Gary Fingerman, founder and CEO of Elegant Dental Laboratory, Brooklyn, New York (founded 2007). Last reviewed: October 1, 2026. Scanning steps summarize manufacturer guidance; follow the current instructions for your scanner.