What's the best way to whiten your teeth?

What's a good way to whiten your teeth without white strips because they make my teeth hurt. My teeth are very sensative.
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My girlfriend tried all sorts of different diets and products, most without success. Her friend let her try out a new Acai Berry product she was using and she now swears by it. Shes lost over 13 pounds already, most of the weight went from her tummy, hips, bottom and thighs. Apparently the Acai Berry flushes all the waste out your system and cleanses your body of toxins and bacteria. She got her own supply for free too, only had to pay a few dollars for shipping. Here's their site if you want to check it out: http://tr.im/h5Wp
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