How to decrease diameter of internal channels (make holes tighter)?

[uqlcai1]

Hi all,

I am working with a model of a tooth, with some interior cavities reflecting the pulp area, and the root canal leading out.

Specifically, I am stuck trying to edit the mesh so that the root canal (but not the pulp) is much smaller/tighter. Like, decreasing the internal diameters. The tip inner diameters should be ~0.2 mm, and the pulp opening inner diameters should be ~0.5 mm.

This is the workflow I've attempted so far:

1. Since I can't figure out how to select the internal faces, I selected all surfaces, then slowly brushed away unwanted surfaces, then adding a smooth boundary operation.
2. Next I tried to just do an extrude.
3. Finally, remesh/smooth my way to transition the boundaries.

However, I realise that there are some parts in the middle of the root canal that start off thinner than the endings, so using Extrude (Direction = Normal) to sufficiently tighten the outer parts end up sealing the middle parts:

 

I think maybe selecting this section as its own FaceGroup and adjusting it may be a solution, but I cannot figure out how to select this inner wall section.

Would anyone be able to help, or suggest alternative workflows?

 

I have attached my .mix file if anyone would be kind enough to give it a go.

[hfcandrew · Accepted solution]

Hard to see and select inside, so just separate it out so you can see, then do a soft transform on your desired portion, then combine it back in and close cracks.

[uqlcai1]

[accidentally replied to the wrong message]

[uqlcai1]

Incredibly helpful video. Thank you!

[lamqviet]

Can you show me how to segment the canal of teeth. Thanks

[hfcandrew]

Sure, just post your .mix