Answer:
The herbst appliance is used to move your bottom jaw forward and your top jaw back. I just got mine a few days ago and it HURTS! Like its the most painful thing and you can have a herbst appliance on while having braces on too! I got braces on and my herbst on at about the same time. With a herbst, you have these like two pieces of metal that go around the tops of your teeth and they stick into your gums and hurt. They hurt because the dentist has to stick the metal part into your gum and cement the metal onto your teeth. Then you have a metal bar that goes across your cheek and connects to the lower part of your teeth with the metal part around it. And that is pretty much what the herbst appliance is and what it does to your mouth. Hope this helps! :)