Dental Mesh Offset Algorithm Development

I need an algorithm that takes a dental model in STL format, recognises a closed margin line already present on the surface, and then carries out three sequential operations:

1. Margin definition & trimming – the code must accurately crop the mesh along that 3-D path and isolate everything inside it.
2. Double offset generation – first create a tiny internal offset for the cement gap (≈0.05 mm), then add an external structural offset for the splint wall (≈1.5–2 mm). The result has to be a single watertight, manifold solid that is immediately printable.
3. Mesh clean-up – before exporting, automatically remove self-intersections, inverted normals or any non-manifold edges that may appear around sharp margins.

I am free on the choice of platform and libraries, so you can use open-source toolkits such as CGAL, Open3D, libigl or your own custom routines as long as the final routine runs headless and outputs a new STL that passes common print validators (Netfabb, Meshmixer, etc.). Please include a short note on the numeric methods you plan to use for offsetting and how you will guarantee watertightness.

Acceptance criteria: supplying a command-line tool or callable function, a sample input/output pair that passes Print3D checks, and clear instructions for integrating the code into a larger dental CAD pipeline.