How does digital aligner planning work?

Digital aligner planning follows the same sequence whether a case is straightforward or complex. Knowing the sequence helps a doctor submit a complete case, read a proposed plan quickly, and give feedback that a planner can act on. This article walks through each step as it happens in a planning service, and points out where cases usually lose time.

1. The case is created

The doctor opens a case with a reference of their own choosing, the type of planning required, and written instructions. The instructions matter more than anything else in the case: they state the treatment objectives, the constraints, and any preferences about attachments, IPR or teeth that must not move. A case number is issued so every file and message can be tied to it.

The difference between a useful instruction and a useless one is whether it names an outcome. "Crowding upper and lower" describes a finding the planner can already see in the scan. "Resolve the lower crowding with IPR rather than proclination, keep the lower incisor inclination as it is, correct the upper midline towards the face" describes the destination and the route, and a planner can build to it without guessing.

2. Scans and records are uploaded

Upper and lower intraoral scans are uploaded in STL, PLY or OBJ format, together with a bite scan or registration. Photographs help the planner read the smile line and the soft tissue, and radiographs are included where root position or bone matters to the plan. The scans are checked for completeness, trimmed if needed, and aligned into the bite.

3. The scan check

Before any planning work starts, the files are opened and inspected. This step exists because a defect found now costs a message, while the same defect found after segmentation costs the segmentation. The check looks for holes at the contacts, missing distal surfaces on the terminal molars, a bite that will not seat on the arch scans, and meshes so heavily decimated that the marginal ridges have been smoothed away. If a case cannot be planned as sent, the doctor is told what to rescan and why, in terms specific enough to act on.

4. Segmentation and setup

Each tooth is separated from the model so it can move independently, with the gingival margin defined and the roots estimated where no CBCT is available. The planner then positions the teeth to the prescribed objectives, checking arch form, contacts and the occlusion between the arches. This stage produces an initial-to-final comparison the doctor can inspect.

Space is reconciled here, not later. The planner measures how much room each arch needs, decides how much comes from IPR, expansion or proclination within the limits the doctor set, and adjusts the final positions until the arithmetic balances. If the instructions rule out every source of space and the crowding still exceeds what remains, the case comes back with a question rather than a compromise invented on the doctor's behalf.

5. Staging

The movements are divided into sequential stages. Each stage keeps every tooth within per-stage limits for translation, rotation, tipping, intrusion and extrusion. Movements that are hard to achieve with aligners, such as rotations of rounded teeth or extrusion, are sequenced with care, and attachments are added where the plastic needs leverage. IPR is placed at the stage where the space is needed.

6. Internal check and doctor review

Before the doctor sees it, the plan is checked for collisions, unrealistic movements and consistency with the instructions. It is then sent for review. The doctor opens it in the browser, rotates the model, steps through the stages and reads the movement, attachment and IPR tables.

An internal check is not a second opinion on the treatment. It confirms that the plan does what the prescription asked, that nothing collides, that IPR is scheduled before the stage that consumes it, and that the attachment list matches the geometry. Clinical suitability remains the doctor's call, and a plan that passes every internal check can still be the wrong plan for that patient.

7. Changes and versions

Feedback is left as comments, either on the case as a whole or on a specific tooth or stage. The planner incorporates the changes into a new version. The previous version is kept, so the history of the case is always visible and nothing is lost between rounds.

Versioning matters more than it appears to. Months into treatment, when a tooth has not tracked and a refinement is being considered, the question is usually what was originally intended for that tooth and what was changed at whose request. A case with an intact version history answers that in a minute. A case revised by overwriting cannot answer it at all.

8. Approval and production files

When the doctor approves a version, the case moves to production preparation. Per-stage models and the attachment and IPR data are exported in the formats the manufacturing laboratory uses. The approved version is locked and referenced by the production files.

Where cases lose time

• Instructions that name findings instead of objectives, so the first version is a guess.
• A bite scan captured after the arches were rescanned, which no longer registers to them.
• Radiographs promised but not attached, on a case whose root position decides the plan.
• Feedback given as an overall impression rather than against a tooth or a stage.
• Approval given by someone other than the treating clinician, which then has to be undone.

Each step exists to keep the doctor in control while removing the technical work from the clinic. A case that arrives with complete scans and clear instructions moves through the sequence in fewer rounds; a case that arrives without them spends its first round establishing what the doctor wants. If you are preparing a first submission, the articles on intraoral scan quality for aligner planning and on what files are required for digital aligner planning cover the intake side in detail.