I might have to give the silver nitrate a shot. Now, about the styptic pencil, that is interesting. I bought a few of those because I am on a blood thinner and the slightest nick with my razor or any scratch I get on me bleeds like crazy. And I use the styptic pencil to stop the bleeding. But what would it do for a canker sore?? I'll let you be the guinea pig, let us know how that works if you get a chance!