How do I stop FFM from sticking cheeks to teeth?

I have three FFMs. A Mirage Quattro, Quattro Air, and a Fitlife. With all of them my cheeks end up stuck to my teeth after a few hours of use. Any ideas how to stop this? I have loosened the straps as far as possible without getting leaks. The Mirage Quattro and the Quattro Air both caused me to get sores on the inside of my cheeks below the gum line. I ordered the Fitlife to see if it would stop the sores. It stops the sores, but it still causes the cheeks to stick to my teeth. The Fitlife is very hard to get to sleep with as it seems to move around with every breath.

I also have a Sleep Weaver Anew that works great at the start of the night, but inevitably my mouth opens enough that I wake up with my chin below the mask and the mask leaking due to no longer sealed around mouth. The best CPAP mask I have used is the Sleep Weaver Anew, but my sleep doctor says I need a FFM due to my mouth opening up during the night. I do get way lower AHI numbers with a FFM when I have actually worn it for a full night.

You can try using Biotene which will moisturizer the teeth and possibly stop the cheeks from sticking to your teeth.

I wonder if you can use a little of the special double stick tape that models
and actresses use to prevent "wardrobe malfunctions". Just between your chin and the Anew.

I wrote the wrong thing about the best mask I have used. The best mask I have used was the Sleep Weaver Elan, not the Anew. It is the nasal mask. The sleep clinic said the Elan leaked too much when I was using it during my second sleep study.

My thought right now is to find a solution for my mouth opening up and go with a nasal mask instead.