I buy boxes of dental floss and my friends make fun of me for my clean teeth compulsion so yeah, I've had more than a few of these teeth dreams, just a fear based dream that manifests as "teeth falling out". You could interpret it a few ways, but i always saw it as people's perception of you from a fearful point, as in "I don't want anyone to see this nasty grille" So it's trying to hide some part of yourself from others that you don't want them to see, and your afraid they will see it. Hope that helps!