Please take a moment and update your account profile. If you have an updated account profile with basic information on why you are on Air Warriors it will help other people respond to your posts. How do you update your profile you ask?
100% A retainer/mouthguard (I'm guessing you grind your teeth at night?) isn't contraband. It might suck for INDOC week, but after that, it shouldn't even be an issue.
The Navy issued me one of those things. I could never sleep with it, but my wife was begging me to get it. I don't know how you do it, but your roommates will probably be glad you wear it.