I'm not sure exactly when I'm getting my braces off (sometime next year) But I'm wondering what my options are for a retainer. I'm planning on joining the military but I can't join until my braces are off and I still can't join if I have a retainer. Is there anything I can get something permanently behind the teeth or use invisalign as a retainer?

P.S. Does every case require a retainer and how long does it have to be worn?

Thanks!