system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do old people keep "chewing" even when they're not eating anything?

I seen a lot of older folks do this, but I never had the courage to ask anyone this, it's kind of a weird question.
gpt
Playing with their dentures.

Similar to when people who have tongue-studs play with them in their mouth, the elderly have the same habit of orally maneuvering their dentures. A better question would be, "what causes people to orally maneuver foreign particles in their mouths?"