this has happened before. There is always the risk of relapse after the braces
are off. Indeed, a retainer can prevent about all horizontal movements. But is
working not so well for vertical movements.
I remember the story of Fyrelight. She was a very active member some time
ago. She had braces to pull down her canines. It worked well, but after she had
her braces removed, a canine moved up again. Probably not what you want to
hear, but she had braces again for some months. It worked out well and I think
things are going well until now. I found this describing it :
A bit the same happened to smile2006 :
BUT, but, not always the braces are installed again. Sometimes they can just
glue some buttons on the teeth and use an elastic to pull it down again. Maybe
that could also be an option for you.