Hey, i wear braces, i had the same problem, its the way you brush your teeth really, u usually get the white streaks when only brushing at one part of the tooth. because the braces get in the way while brushing you have to make sure you brush below and above the brace. It works alot better if you are using a Electic toothbrush (oral B) and also your orthadontist can sell you a brush head specifically for braces. also he might also have a special mini brush for inbetween the wire.
Hope this helps
make sure to brush after every meal and after you drinks things that have color (fruit punch, coke, juice).....also when you get your braces off they are going to clean your teeth and put a stain remover on them, your teeth are going to be darker then the little squares (brackets) are.... just make sure you brush REALLY well...