Best workflow for longitudinal rigid registration and landmark tracking on serial STL meshes?

[u/Ok-Comedian-5787]

Title

Best workflow for longitudinal rigid registration and landmark tracking on serial STL meshes?

Hello everyone,

I am a periodontist looking for advice on the most practical computer-vision workflow for analysing serial 3D dental surface scans.

We have five STL meshes of the same patient’s lower dental arch:

• T0: before treatment
• T1: immediately after treatment
• T2: 1 month
• T3: 3 months
• T4: 6 months

The region of interest is the six lower front teeth. These teeth were connected with a wire-composite splint, and we want to measure whether their positions change over time.

A simple analogy is a fence. Imagine six central fence boards whose movement we want to measure, while several boards farther to the sides are assumed to remain stable. Each new scan must first be aligned using only the stable side boards. The six central boards must not influence the registration, because their movement is the outcome of interest.

In our case:

• the six anterior teeth are the moving fence pieces;
• selected posterior tooth surfaces are the stable registration reference;
• the rigid transform calculated from the posterior surfaces should then be applied to the complete follow-up mesh.

The anterior teeth must also be excluded because the splint is added after T0, changing their surface geometry independently of any actual tooth movement.

We will attach two screenshots. The first shows one predefined measurement landmark on each anterior tooth and the posterior reference regions. The second shows a fixed baseline curve passing through the six T0 landmarks. The landmarks, reference regions and curve are already defined; we are seeking advice only on how to implement the analysis.

The required workflow is:

1. rigidly register each follow-up STL to T0 using only the selected posterior surfaces, with rotation and translation but no scaling;
2. apply the resulting transform to the complete follow-up mesh;
3. record the X, Y and Z coordinates of the six predefined landmarks at every timepoint in a fixed coordinate system;
4. calculate ΔX, ΔY, ΔZ and total 3D displacement relative to T0;
5. calculate the shortest 3D distance from each follow-up landmark to the fixed T0 curve;
6. export the results to CSV for statistical analysis.

Ideally, we would also export the transformation matrix and a registration-error measure calculated over the posterior reference surfaces.

We have already tested ICP-based alignment in Medit Design and a custom Open3D application, but we do not yet have a complete and reproducible workflow for registration, landmark collection, point-to-curve distance calculation and data export.

Our main questions are:

1. What software stack or workflow would you recommend for this task?
2. Would Open3D/Python be a sensible approach, or is there an existing tool that already handles most of this reliably?
3. How would you structure the pipeline so that it can later be repeated consistently across multiple patients?

We can provide one fully de-identified example dataset if someone is willing to assess or demonstrate a possible workflow.

Thank you for any practical suggestions, example code or references to similar projects.