What is a good brand for teeth whitening and do they actually work?

I was thinking of buying some at a drugstore, but I've never used them before and really have no knowledge about how effective they are. My teeth have always been mildly yellow, and until I'm able to go the dentist, I was thinking about trying something that's a little bit more convenient for me in the mean time. Any suggestions?
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Oh, and something that's reasonably priced, I heard crest whitening strips are around $50. Are there any that's a little more cheaper? If not, I guess I have to invest a bit
What is a good brand for teeth whitening and do they actually work?
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