How do I find a dr. dentist who will treat canker sores?

I get canker sores quite a bit, usually I just deal w/them on my own, using OTC stuff to help w/the pain and eventually they will go away. But once or twice, a while back, I had a doctor who basically froze them off. It hurt like a you know what, for a split second but then that pain subsided and the sore was gone w/in an hour! However, I don't see that dr. anymore and I haven't been able to find a dr. dentist who treats canker sores in this manner. How would I go about finding one before I even make the appt? I'm in so much pain now w/one or two, I've been getting them one right after the other alot lately. It's making me so depressed, hurts to eat and talk. Help!
Just wanted to say it wasn't really freezing the canker sore, they did something to cauterize the sore and it went away almost immediately. I understand the diet part, I'm sure that's part of my problem but also stress can cause them to appear and this cauterizing treatment at least will help get rid of them quicker so I can be out of pain as soon as possible.