In general, we want to put our tongue to the roof of our mouth to make a circuit between the Conception Vessel and Governing Vessel. These are the meridians that run up and down the midline of the front and back of our head and torso, respectively. Putting the tongue to the roof will help the enegy flow better between the two.
I'd suggest doing the exercises with and without the dentures a couple of times and see which, if any, feels better to you.
