Manufacturers were asked to produce evidence as to the effectiveness of their products. In three of the products tested, independent dentists received no evidence the products helped whiten teeth. Teeth can become discoloured for several reasons, including age, diet and lifestyle.
Some prescription drugs can also affect teeth colour.
William Hague shows off his pearly whites Tooth whitening products are divided into those which promise to whiten, and some just claim to remove stains. Stain removal often involves the use of abrasive agents that simply rub them off. Otherwise you could be washing money straight down the plughole. Teeth can also be cleaned professionally by a dentist or hygienist to remove stains. Toothpastes alone cannot offer more than a transient cosmetic benefit.