I'm assuming you're talking about canker sores. I don't know how much help this will be to you, but here it is anyway: You may have tried these, but I've found

I'm assuming you're talking about canker sores. I don't know how much help this will be to you, but here it is anyway: You may have tried these, but I've found the best ways to dull the pain are swishing 50/50 Maalox/Benadryl and using a styptic pencil. Also, I've found in my case that what helps most to prevent them is keeping my mouth as clean as possible. The two main causes I've identified are illness and physical trauma to the tissue. The worst offender is the crap plaque excrete; it eats away at tissue, and I've found more than a few new sores under a stray piece of lunch. Oh, and I've had far fewer sores since I switched to an SLS-free flavour of Sensodyne.