Ask your dentist/orthodontist for Opalesense Tooth Whitening. My mom works for a dental office, and to keep her teeth white ('cause obviously people that work at dental offices want to have clean teeth) she uses it and it works as far as I can tell. I have braces, so I can't use it, but I definitely will when I get them off.
I was told by a dental hygienist. No matter what u try to whiten your teeth with they can't get any whiter then how naturally white they already are. Hope I explained that right. Basically they can't get any whiter then there natural color
Use whitening toothpaste and make sure you brush twice a day and for at least two minutes. Use a soft bristle tooth brush and don't brush too hard or you will wear away the enamel and under the enamel your teeth are brown and once it's gone enamel never comes back