Having a full denture upper for 3 yrs, it's suddenly feeling kind of larger than it was to the point where i have to use adhesive.do gums change sizes?

Yes: Your bone will continue to shrink your whole life, but it shrinks the most just after the teeth are removed. Your body interprets the fact that you don't have teeth as you don't need bone. You can expect to periodically need to have the denture relined and then replaced.

Absolutely: Bone volume shrinks over time due to the missing teeth. It's easily remedied by having the denture relined. Speak to your dentist. Wearing an ill fitting denture can accelerate the lost of bone, so it's better to have a well fitting denture than using gobs of adhesive. All the best...

Bone resorbtion: When teeth are lost, the supporting bone tends to resorb (shrink) over time. A poor fitting denture or an imbalanced occlusion (bite) hastens the process. See your dentist to have your soft tissues, bones, gums, bite and denture evaluated. Too many patients think that just because they have no teeth they do not need to see a dentist regularly. NOT TRUE.

Of course: The bones and gums in your mouth change over time, but the size of the denture stays the same. Denture relining is an important part of denture maintenance every few years.