When partial dentures start getting loose or uncomfortable, it’s usually because the teeth that support them are getting loose.
When full dentures are getting loose, it’s typically because the underlying bone is breaking down.
The breakdown is natural. Your body naturally works in cycles of breakdown and regeneration. For example, body builders go to the gym and work out, which triggers a breakdown phase. The breakdown triggers a regeneration phase, which builds the muscle mass.
As we age, our breakdown phases speed up and our regenerative phases slow down.
This affects the bone that supports your teeth and dentures too. The bone breaks down faster than it can be regenerated. Eventually, there’s not enough bone to support dentures.
At that point, you can get implants that will hold the denture in place. With implants, you can get back to a state where you can chew comfortably.