The external darkening of the teeth is caused by substances such as coffee, tea and cigarettes. These can be cleaned when you visit your dentist for a general tooth cleaning. The internal stains are caused by genetics and age; the older people get, generally, the darker the teeth become. This is where  dental bleaching comes into play.

In some studies, patients have experienced uncomfortable short-term side effects when having teeth bleached. Hydrogen peroxide can increase temperature sensitivity in the teeth, particularly at higher concentrations, and night guards often cause gum irritation. Other than these minor and often rare side effects, the general health risks of bleaching systems are minimal. Applications are controlled so hydrogen peroxide is not swallowed, the associations said.

Overzealous use of over-the-counter home bleaching products can wear away tooth enamel, especially with solutions that contain acid. Therefore, bleaching is a procedure best done under the care of an oral health care professional.

Whitening toothpaste can effectively keep the teeth cleaner and, therefore, looking whiter. The stronger tooth pastes rely on abrasion to remove external stains, as opposed to actually changing the color of teeth. The key, is to study a product's ingredients and look at your teeth to see if it changes their color. Then consult an oral health care professional for customized advice.

Many dental benefit plans do not cover the bleaching of teeth, considered aesthetic dentistry. It recommends continuing a program of preventative dental examinations with a dentist and consult them before starting any type of whitening methods.