What is the most effective teeth whitening product?

I prefer something I can get at Wal-Mart. Like: Crest, Aqua Fresh, etc.
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Crest White Strips work well. If you have sensitive teeth, I recommend that you use them only every other day or every two days as they can cause pain. I personally prefer Go Smile. You can find it online or at any Sephora; it's more expensive but convenient, sanitary, and great for people with sensitive teeth like myself.
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