I was giving a presentation at work when my front teeth started to crumble. I kept talking and covered my mouth with my hand, hoping no one would notice. My manager sat in the front row, smiling as if nothing was wrong.
This dream may be about a fear of looking less capable than you'd like at work: you keep going and hide the problem rather than stop. Your front teeth crumbling mid-presentation carries the dream most clearly (front teeth are the ones everyone sees when you speak, so losing them can stand for losing face).