Extrude problems

[eamadorgoytia]

Hello, i´m a dental surgeon and i use MM to make cx guides in mandibular and maxilar stls.
i have a problem when i try to extrude a selected part with mi guide for the cut in the surgery. i really want to know if there's a way to extrude the selected part to make a uniform guide with a lot of extended borders like you can see in the picture. thank you very much!

[hfcandrew]

Wrong tool, use Offset: https://help.autodesk.com/view/MSHMXR/2019/ENU/?guid=GUID-749E6C72-D82B-4FA9-A157-1AE612B779AE

[eamadorgoytia]

Thank you for your help, but i still have the same problem even using offset, i don´t know why it keps making the positive offset with irregular borders. Any guess?

[eamadorgoytia]

even selecting a part without marking the cut for the surgery, the offset is made with irregular borders.

[hfcandrew]

Remesh the group first. You can get sliver triangles around the perimeter that mess up an offset after smoothing a boundary. Look at it in the wireframe.