Canker sores are indeed terrible. I have some simple advice given to me by an oral surgeon about their healing:

  1. Do not use hydrogen peroxide. Although it will quite effectively numb the pain if you rinse with it for about 30 seconds, it will about double the time you have the canker sore for. This is a bad thing.
  2. Ordinary mouthwash can also slow healing. The alcohol present obstructs your skin's attempts to heal.
  3. A swig of liquid benadryl, rinsed for about 30 seconds and spat out (unless you want to feel drowsy and allergy-free for a few hours) will relieve the pain without obstructing healing. It's cheap, simple, and makes the pain stop.

Also, I've found that braces and canker sores can be a terrible combination. Braces irritate mouth tissue, and if a bracket is digging into a sore, it's very painful. A little wax will do wonders. If your orthodontist didn't supply you with some, most grocery stores and druggists carry small packages of wax.