they were not that crooked. they needed pulled back and a couple molars needed untwisted. i also had my "fang teeth" (hee hee) pulled down.
it was so wierd when i first had the braces put on because the brackets were not in a strait line so my teeth were kinda turned a little bit this way and that.
i should wear retainers BUT my wisdom teeth are coming in and i dont have the $$ to have them removed. so i dont wear my retainer anymore. they are not as strait as they were when i got my braces off. but they are not as crooked as before the braces either. i probably will get that invisaline retainer system in the future. its made of molded plastic: http://www.invisalign.com/generalapp/us/en/for/index.jsp
right now i am just letting them shift as my wisdom teeth come in.otherwise i get headaches and i would rather have a little bit of crookedness going on for now than be dealing with the pain of an impacted wisdom tooth.
you could be grinding too because of tension,parasites,jaw structure etc. there are alot of reasons for it. you can buy a mouth guard to sleep in if you grind you teeth when you sleep. i have never seen one...but you could look into it.