I used to get Canker sores (from as young as I remember to 32years of age)about every three weeks and they would last about 7-10 days. They usually started when I would bite my lip or cheek.
That was a year ago.
Now I only get the start of them every 8-12 weeks. Lets say I bite my cheek, I have that feeling and taste with my tounge that it will turn into a canker sore but it never does. I had tried everything under the sun that you could buy over the counter and nothing worked.
What I did is on OCT 4th last year I quite drinking soda. I know it sounds crazy but thats what I did and the cancer sores stopped. I am now using a natural tooth powder to brush (Eco Dent).
I think it was the carbonation that caused my cancer sores I drink a little coffee with Sugar and haven't had any problems with them.