Teeth whitening is a procedure used to lighten the color of teeth. It can be performed professionally in a dental office or with over-the-counter products at home. Teeth whitening can be effective in treating stains and discoloration caused by smoking, coffee, tea, red wine and other factors. However, it is not effective on all types of stains and can have side effects such as temporary tooth sensitivity. It is important to talk to a dentist before attempting any teeth whitening procedure.