Roger Tran, DDS

Hi! 
It is hard to tell how many tray you need for correction.  My average for a full case is 20 trays.  If you have only 12 doesn't mean you won't have full correction.  Hope that helps!

Hi!  If you are not getting results with over the counter whitening, you probably need professional whitening.  Try zoom whitening or Kor whitening.  It should get you better results.

Hi!  Yes this is serious!  It looks like a bad cavity.  Please go to your nearest dentist.  Thank you!

Hi!  Pain in previously root canal teeth with cold sensitivity usually means there could be an active canal not seen on previous treatment.  X-rays don't show everything so it doesn't mean you have no infection.  It means the X-ray detected no infection when there might be infection there but too small to detect.   A cone beam 3D X-ray might give you answers whether you have reinfection or not.  

I suggest having an endodontist  with 3D X-ray help you.

Hi!  So you have some pain.  This could be:

-reinfection of root canal
- gum problems in the area
- biting or grinding
- cracked tooth

you should always consult a dentist because waiting usually costs more money.

Hope that helps!