Hi,
I'm not a big fan of the game ready teeth available with CC3, so I would like to grab the default higher poly teeth, import them into Blender, simplify them as I see fit and then bring them back into CC3 to use on all my characters. Is this possible? I've been searching the forums and on YT and I haven't found any help.
Thank you!

Got to have those 2 for Blender round trip:
1. CC3 add-on for Blender: https://forum.reallusion.com/FindPost475005.aspx
2. Blender AutoSetup plug-in for CC3: https://forum.reallusion.com/FindPost500772.aspx

And then Export character from CC, Import to Blender using (1), tweak Eyes/Teeth, Export from Blender again using (1) and Import back to CC using (2).
Then save eyes and teeth as custom assets to use on other characters.

Note: You can freely change face count for eyes and teeth in Blender, but not for the body. If you change face count for the body, you would not be able to return it to CC.