I've had the same nightmare over and over again for the last 10 years. My teeth are falling out, and I'm either at work or in a public setting. I completely panic. In my dream, I'm just spitting my teeth into my hands or pulling them out with my fingers because they are broken and loose.
I always feel a tremendous sense of relief when I wake up and all of my teeth are still in their place. I've read that dreams about your teeth can be stress-related, and I've always just assumed that was the cause. I've learned to live with it.