Has anyone had teeth whitening? What is the truth,does it hurt, how long does it take,what is the aftercare?

And which is the best to have?
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teeth whitening is a bad idea i asked my dentist this and they said it gives ur teeth and gums a better chance of getting mouth cancer and that it makes your teeth weaker witch will need lots of aftercare they recommended using a teeth whitening toothpaste with regular brushing
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