go into the Shape tab of that ugly toothed Lisa model, type "realism" in the search bar, there will most likely be at least one morph named "mouth realism" or similar dialed to 100% (and black 100%, meaning it is a default value), dial them back to 0 and check if that fixes the teeth
If that problem is present even with default G8 figures in an empty, new scene, then it could be a result of using XTransfer script to convert G3 morphs to G8, you'll have to find and delete the offending morph from where the script put it
If that problem is present even with default G8 figures in an empty, new scene, then it could be a result of using XTransfer script to convert G3 morphs to G8, you'll have to find and delete the offending morph from where the script put it