If you want your whitest teeth ever use baking soda it may be slightly abrasive but it works just scrub really hard once or twice a week.
Never scrub your teeth ... never brush your teeth hard. All you're achieving is damage to the enamel and when that's worn, your teeth will never be able to look white. Plus while scrubbing your teeth, you risk damaging your gums, with the long term result being the gums shrinking and this may lead to teeth becoming loose and those falling out.
If you want to use a little baking soda, use it on a soft toothbrush, or disolve it in some water and brush gently.
After 5 years, 11 months and two days of stainless steel brackets ... my teeth now have upper and lower bonded, gold wire, retainers and removable clear retainers!
Yep, never be abrassive to your teeth. You'll end up with tooth sensitivity