What files are required for digital aligner planning?

Every digital aligner case starts with files. Sending the right ones, in the right formats, is the single biggest factor in how quickly a case moves from intake to a reviewable plan. This is what a planning service needs and why.

The scans

Three scans are needed: the upper arch, the lower arch, and a bite scan that records how they meet. Most intraoral scanners export these as STL, the most widely used mesh format, or as PLY, which can also carry colour. OBJ is accepted as well. A planning service works from the mesh, so the format matters less than the quality of the capture.

A short note on the formats, because it occasionally matters. STL stores only triangles: geometry and nothing else, which is why an STL of a scan looks uniformly grey. PLY and OBJ can carry per-vertex colour or a texture, which is genuinely useful to a planner reading gingival margins, existing restorations and decalcification straight from the model. If your scanner offers a colour export at no extra effort, send it. If it does not, STL is entirely workable and photographs fill the gap.

Export at the scanner's normal resolution. Some export dialogues offer a reduced or lightweight mesh to make the file smaller, and that setting removes exactly the fine surface detail — marginal ridges, cusp tips, contact points — that segmentation and attachment placement depend on.

What makes a scan usable

• Every tooth captured completely, including the distal surfaces of the last molars.
• Enough gingiva to define the margins, without holes or stitching artefacts at the contacts.
• A bite scan taken with the patient in their habitual occlusion, not a strained one.
• No missing data under saliva, blood or a tongue that moved during capture.

The bite scan specifically

The bite is the record that relates the two arches, and it is the one most often sent in a state that cannot be used. A buccal bite scan taken on one side only can leave the registration free to rotate; scans taken on both sides constrain it properly. If either arch is rescanned or re-exported after the bite was taken, the bite no longer registers to it and has to be retaken. And a bite captured while the patient is posturing forward or biting on a cotton roll records a relationship the patient does not have, which then propagates through every occlusal decision in the plan.

Photographs

Intraoral photographs of the front and both sides in occlusion, and occlusal views of each arch, let the planner read what the mesh cannot show: the gingival health, the smile line, and any restoration that affects where an attachment can be bonded. Facial photographs at rest and smiling help with midline and incisal display decisions.

Photographs also settle arguments the model cannot. A mesh shows a crown; a photograph shows that the crown is a full-coverage ceramic restoration, which changes the attachment plan. A mesh shows a gingival margin; a photograph shows recession and a thin biotype, which changes how far that tooth should be moved buccally. Sending them is a few minutes that regularly saves a review round.

Radiographs

A panoramic radiograph is useful for root angulation and pathology; periapicals help where a specific root is a concern. A CBCT is not required for most cases, but where it exists it improves the estimation of root position. Radiographs are sent as images, DICOM or PDF.

Send them whenever the plan will move roots rather than crowns: significant uprighting, torque changes, space closure through an extraction site, or any movement adjacent to an implant, an ankylosed tooth or a root that is already converging on its neighbour. In those situations the difference between an estimated root and an imaged one is the difference between a plan you can rely on and a plan you are hoping about.

The instructions

Files show the starting point. The instructions define the destination. Write the objectives, the constraints, the preferred method for creating space, any teeth that must not move, and your position on attachments in the aesthetic zone. A short paragraph of clear intent saves a full review round.

Include the things that are true of the patient rather than the model: an implant that cannot move, a bridge that must be kept intact, a tooth with reduced periodontal support, a history of root resorption, an upcoming event that fixes the timeline, or a patient who has already refused visible attachments. A planner cannot infer any of these from a mesh, and each of them changes the plan.

What delays a case

• A bite scan that does not match the arch scans, usually because the arches were re-scanned after the bite.
• Scans exported at very low resolution, or with the base trimmed through the gingival margin.
• Missing distal molar surfaces.
• Instructions that describe the problem but not the desired outcome.
• Patient-identifying information in file names, which then has to be removed.
• Archives that unpack into an unlabelled pile, so upper, lower and bite have to be guessed.

Name the files for what they are — upper, lower, bite — and keep them with the case rather than in an email thread. It sounds trivial until a case has three uploads and nobody can tell which scan is the current one.

Use a case reference of your own rather than the patient's name in file names and in the case itself. The planning service does not need to know who the patient is, and keeping identifiers out of the files makes the record easier to protect. For what separates a scan that plans cleanly from one that has to be rejected, see intraoral scan quality for aligner planning.