Whitening is not a good option for people with untreated tooth decay or gum disease. Not only are whitening agents ineffective for people with certain dental diseases, but they can also cause hypersensitivity in teeth. So a dentist will need to work on improving the health of the teeth and gums before addressing any purely cosmetic matters.
Others who might need an alternative solution are those with stains from taking certain antibiotics, like tetracycline, as a child; those who experienced some kind of trauma to their mouth or people who have had bonding or tooth-colored fillings in their front teeth. While whitening might make these teeth a little lighter, it might not provide even results. Experts generally recommend using porcelain veneers that completely cover the affected teeth.
For most people, however, tooth discoloration can be chalked up to the passage of time and a habit of eating dark or brightly colored foods, like blueberries or cherries, and drinking certain liquids, like red wine, coffee or tea. Another culprit is cigarettes. White-teeth seekers in this group are considered good candidates for whitening techniques. People with yellowish teeth are thought to be the best bleaching candidates, followed by those with brownish-colored teeth and then those with grayish teeth.
According to the ADA, people should not experience tooth enamel damage or side effects beyond temporary tooth sensitivity and gum irritation. Some researchers have raised concerns about the peroxide in the bleaching solution being linked to oral cancer, but no clear connection has been established.