I had braces when I was a kid, but my bottom teeth had moved quite a bit since then, one tooth turning sideways and others becoming crooked. I had a few people over the years tease me about my 'vampire' teeth -- a couple of teeth I didn't realize had started to seem like they were sticking up because they were turning. It doesn't happen overnight, and the first tray or two hurt a bit at first, but after that it was completely painless. I was supposed to wear the trays all of the time except when eating, but I only wore them about half of the time while at work. The Dr. only had to lightly file the space in between a couple of teeth. Not enough to notice, but enough to let the teeth move. Two years later, my teeth are beautifully straight and look great. No vampire teeth! And I only wear retainers at night! Awesome.