What do you use for UV mapping? UV Mapper? Can't you just select the teeth by material and isolate them that way?
I made the current UVs for Antonia (after v117, at least as of version 118, which I would assume is what v120 has). I used UVLayout Pro on the low res version and didn't need any morphs to get at the teeth, since with UVLayout you can just strip away geometry that's in the way and put it back together later. Not doubting you, just not understanding what you mean.

However, I made an open mouth morph for Antonia hi res, by rigging the mouth with joints in Lightwave and deforming it with the bones, as opposed to dragging points around. That morph is still on the dev site somewhere, I think. I could easily enough attach that rig to the low res version and make you an open mouth version for low res Antonia if you'd like.