@derekfnord: Your theory is not outside the realm of possibilities… which would reinforce that stress is the root.
I have had this dream once, several years ago. I am not a tooth grinder, and my teeth and jaw were not aching when I woke up. The man I lived with at the time did not observe any sleep-behavior changes that night, so I am doubtful that I was grinding my teeth when the dream occurred.
I tend to believe that most dreams are random and irrelevant. As such, I pay them very little attention and rarely remember them. But I have had dreams over the course if my life that related to my childhood abuse and other incidents. So when I have that rare, particularly emotional or vivid dream, I do pay it heed. In my life, those dreams have brought issues to the surface when I was ready to address them. The night my teeth crumbled and fell out (@Cupcake: I can’t remember if I swallowed them or not), I did a little research, and found, as @RedPowerLady did, that this is one of the most common dream images, hence my original comment.