I used to have that same dream quite frequently. It started before I even had all of my adult teeth as I would dream I had wiggled free what I thought was a baby tooth, but it was really an adult tooth. As I got older they would sometimes crumble, other times a whole tooth would be hanging on by a thread.

I used to spend a lot of time trying to figure out what these dreams meant. Then I asked myself how I feel during these dreams and determined I feel a loss of control. I feel like no matter what I do, my teeth will crumble, it's humiliating.

Perhaps my teeth falling out dreams signify the loss of control in my real life, or perhaps if means nothing at all.