Bi Carb soda, Lemon, or salt to whiten and brighten teeth?

I want to whiten my teeth a little. I have been reading that using bi carb soda, salt or lemon can damage teeth but how often can you use them with out damage.
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No Lemon!!! Citric acids damage the teeth enamel......patients that suck on lemons have horrible teeth! Baking soda and salt are pretty much the same..... We reccomend taking a box of baking soda and a bottle of hydrogen peroxide and wetting the brush with the peroxide, then dipping it in the baking soda and using that to brush....
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