A significant percentage of humans have occasional dreams about their teeth falling out -- no one really knows why.
This guy might be having that dream right now. Spoiler <iframe width="624" height="351" scrolling="no" frameborder="0" src="http://finance.yahoo.com/video/billionaire-millionaire-one-day-135558362.html?format=embed&player_autoplay=false"></iframe>
My GF told me the same thing the other day and said that she hadn't heard about it until about a year ago and since then she has had a lot of teeth falling out dreams.
Some people have a fear of peanut butter being stuck to the roof of their mouth, I kid you not. Arachibutyrophobia: http://www.fearofstuff.com/food/fear-of-peanut-butter-sticking-to-the-roof-of-your-mouth/