I stopped using my electric toothbrush (or rather, I still use it manually) because it was sort of traumatizing my gums. I switched to Burt's Bees toothpaste because it doesn't have SLS, which I read is part of the problem. I don't recommend Burt's Bees toothpaste for other reasons but I think it has helped a little with canker sores.
A physician's assistant told me to try using Oragel and taking L-Lysine when I feel a canker sore coming on. I've had good luck with both of those too.
Sorry for the length. It's been a looooooong week and I'm too exhausted to move my cursor to the post button so I'm just chattering away now. la la la la la la la.....