Please don't mention Listerine as that stuff doesn't work for me. Serious replies only. Thanks.

Im asking this because im going there in a couple weeks and ill be gone for 22 days. im and staying in hong kong, shanghai, xi'an. ive seen picture of smog and haze. is it bad for your respiritory system to breath in that air?

While having my braces fitted a few days ago my orthodontist showed me that I have a hard white crust on the bottom of the back of my bottom teeth and that I should get my dentist to remove it, although I can't rememeber what it was called.

is it?