Is Tooth Whitening Safe?

Most studies confirm that tooth whitening is safe and effective. Whitening gels that contain 10 percent carbamide peroxide (equivalent to 3.6 percent hydrogen peroxide) have not been shown to cause any damage to the enamel of the tooth. Higher concentrations of carbamide and hydrogen peroxide available from the dentist may weaken the enamel, but most of these formulas also contain fluoride offsetting this potential side-effect. People who use higher concentrations of whitening agents can also receive prescription fluoride gels from their dentist to help further protect their teeth.
If tooth sensitivity or gum irritation occur, it is best to start using the whitening product less frequently -- say, every other day instead of every day -- and reduce the amount of time spent whitening. Prescription fluoride is also used to treat sensitivity sometimes associated with tooth whitening. Irritation of the gums can occur from either the in-office, at-home or over-the-counter tooth whitening systems. Gum irritation is usually mild and reversible, but can be treated with over-the-counter products such as Orajel.
Article taken from: http://science.howstuffworks.com/innovation/everyday-innovations/tooth-whitening4.htm