My aunt gave me those whitening creams from her dental office - didn't work for nothing.
I bought the strongest whitening strips from Crest - that's meant to be used for 14 days. My only trick, since my teeth weren't sensitive from the product, was that I left it for 20 minutes longer. I just never let it touch my gums. Unfortunately atm, my teefus aren't white like they were before

They're a tint of light yellow... grossness.
Rosers, the price differs here. It depends what you want too. But the average cost is $24 I believe?
Anders, $20?! Holy hell. And our dollar is low... so you guys really do get a bargain shopping through US stores.