What is the best teeth whitening product that can be bought in grocery/drug stores?

I don't want to pay my dentist to whiten my teeth, but I also don't want to buy something from the store that won't work anyway.
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I have tried many whitening products, and i have to say the best ones are Crest Whitestrip Renewal and Crest White Strips Advanced Seal, the Crest White Strips Renewal is cheaper, and work just as good.
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