Maybe the British have a thing about teeth - if you look at another submission, you'll see that's about teeth too!
Habits can be changed - it's known that it takes 28 days to get into a habit, so it must stand to reason that it takes 28 days to get out of one. You need to decide that you want to change that habit, and then have the belief to do it.
Brushing your teeth, maybe you can just talk to yourself instead - yet another strange habit though I think. Good luck!
