I used to suck my thumb too, ever since I was a wee lass. I had to have brace because of it but I still didn't quit, he he. I had to stop because my poor teeth were getting pushed forward after being all nicely straightened by the brace, my jaw was going a bit funny too and my dentist kept making dissaproving 'tsk tsk' noises. It's so hard to stop because I used to do it without even thinking about it. My little cousin has to wear mittens to bed to stop him doing it at night, he calls them the magic mittens.
Hehe yea i should have had a brake but my authodontist was mean and wouldnt give it to me cos he "knew" (*rolls eyes*) i was still sucking my thumb. That was back when i was 15/16. Now my front teeth are forward a bit and my bottom ones are crouded back. They dont look super gross they just hurt at the bottom. The reason why i didnt bother bothering him for them back then was because i figured i didnt care how it looked but now its getting painfull things HAVE to change.