I wear upper dentures AND have TMJ. My new Sea Elite reg is great because it is lightweight but the regs I used to certify (Aqua lung I think) with were awful: Hard to keep in my mouth and caused very sore jaws.
There are mouthpieces available that do not require biting/clenching that I want to try and I am thinking of putting a swivel on my primary reg hose to eliminate the push/pull from the hose.