What works better for teeth whitening?

What works better? Aquafresh white trays or Crest white strips? They both work in seven days, but what makes the whiter?
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I started using gel trays to whiten my teeth but couldn't prolong the treatment because of tooth sensitivity. It was unbearable therefore didn't try them again. You can do harm not only to your teeth but your soft tissues. There are better alternatives like home whitening kits, over the counter whitening products… Stick with teeth whitening made from natural ingredients.
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