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I am trying to make a surgical cutting guide (blue) for a jaw bone (white). The top part has to fit on the teeth, the lower part on the side of the jaw bone.enter image description here

However, when I use the Boolean Difference modifier, it only partially works: The teeth are nicely cut out from the upper part, as you can see below.enter image description here

But the part that touches the mandible is left open after the boolean, as you can see below.enter image description here

I guess it might have something to do with the jaw bone model coming from a CT scan so it has an internal (hollow marrow) structure (see below)enter image description here

I don't know how to solve it though. Is there a way to just 'fill' the jaw bone model and make it completely solid? Thanks for any advice.

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  • $\begingroup$ Blend is always wellcomed, but in this case I'm not sure about a size. Try to check if bone has any hole, if so fill them. BTW was it substract with open part or just it left open without substract? $\endgroup$
    – vklidu
    Commented Feb 3, 2020 at 23:56
  • $\begingroup$ If the mesh is hollow, have you tried applying a solidify modifier? Judging from the surfaces though, you may need to boost the clamp property for the modifier - which may prevent you from adding much thickness $\endgroup$
    – stphnl329
    Commented Feb 4, 2020 at 1:59

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Booleans ussually fails on non-manifold mesh.

To see these problematic parts - from within Edit Mode, using Vertex selection, with no geometry selected, Search for "manifold" (Select non-manifold operation appear). For more info see Blender Manual

enter image description here

Q: Is there a way to 'fill' model and make it completely solid?

A: In a meaning - closed mesh without holes - Yes

_ Fill

Search for Fill operator and increase number of vertices in tool properties until the holes are filled. Like here it was value 14.

enter image description here

But N-gons are not the best for boolean operations so probably better to try ...

Grid Fill

Like here. Important for this function is to have a loop of even number of vertices. If you don't have, you can select one edge and subdivide it. (White vertex in the screen is one I added.)

enter image description here

Or even better to Triangulate whole mesh Ctrl+T

Remesh

Or you can try Remesh modifier > Sharp if there is too much work, but even on hi Octree Depth in wouldn't be precise.

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But that's normal, right? The boolean asks you which mesh you want to substract by which other mesh. So it's notmal that the lower part of your blue mesh is substracted from, if it touches the jaw bone. If your goal is to keep that from happening, so that only the teeth make an imprint, I suggest you select your teeth, even if roughly, and press P, for seperate, and "selection", so the teeth you selected are now their own mesh, you can rename that teeth. Now this time using the boolean modifier, you select the teeth mesh and not the jaw mesh, and only the teeth will make a mark. You can now in object mode select teeth and jawbone and press ctrl+J to join the meshes together.

That may not be the best way to do it, but that's what I'd do. Though I hope I didn't misunderstand your question.

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you design your splint for mandibular resection and do not make the slot for the bone saw, do the boolean with teeth and jaw bones, after that apply the box you already added to make the slot and boolean it again from the splint.

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