Hi ktealby 
I suppose it depends on what maximum polycount you feel is needed for the animation you want…. and to figure that out, you need to do some experimentation, although, as teeth go,.. the pup’s teeth are pretty low poly,.
It’s perhaps also important to remember that the Daz Pup, and several other figures, were built as (Sub-D) figures, which allows them to use subdivision smoothing at render time, to refine the appearance of the mesh (make it less boxy).
so,. it’s not really a (high) polygon figure to begin with,. and that may make the process of reducing the mesh ,.. tricky.
Looking at the teeth,. I think it may be easier to select edges and use dissolve, rather than the decimator in carrara,. which can be a bit of a blunt instrument.
As Head Wax pointed out, you can unlock the figure protection, (using Edit /Smooth) or,.. Fenric has a plug-in to allow you to “break in” to the figure,... then you can experiment to see what works.
making the Old teeth, invisible using the shader is a nice idea,. but I think you’d still need to delete and replace them, to export the final (low) mesh.
There’s also a Decimator tool available for Daz Studio, which was designed to reduce figures for game development.
and as far as I know, that works on the figure and rigging and retains the UV’s, and creates a “LOD” version.
it may be worth checking out.. (see pic)
As for the legality aspects,.
I just think it’s important to point that out at the start of the process,. rather than later..
Mesh reduction for games is a common question,. but, so many times the user is either unaware of the fact that they don’t “Own” the model they’ve “purchased”... or that they need a developer licence for game production,. .. or that “Not all models” can be used for game development.
I like Roygee’s suggestion of building your own,.. then you avoid lots’ of possible issues, ..and don’t need a licence.
Hope it helps 
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