This is a real problem, and has certainly not been fixed to my knowledge.  It happens for me in both P6 and P7.  It happens for both the teeth set and for any prop hair.  It does NOT happen for me unless I use Point_At for the eyes (though I haven't tested whether it happens when using Point_At for any other body part or prop).  Oddly enough, the teeth and hair pop back in place for the frame I'm in if I switch cameras then rotate or otherwise move that camera.  Then I can go back to the original camera.  Needless to say, that is not an acceptable workaround, especially since it only works for still shots.