People who work at keeping their teeth want them to look good. Today, bleaching accounts for more than half of all cosmetic dental procedures performed in the United States.

You can have your teeth bleached in one of three ways, or by using a couple of the options in combination.

Most dentists offer "power-bleaching," in which 35 percent hydrogen peroxide is put on gauze and placed on the tooth. The whitening is then activated by heat or light, often by a laser. Treatments take about 35 minutes, and four to six visits are usually needed.

Many dentists believe that a less expensive treatment -- in which patients wear custom-fitted mouth-guard trays containing a whitening agent -- works just as well. In this procedure, an impression of your mouth is made in a plastic mouth guard. A tasteless liquid whitening agent is poured into the mouth guard and worn either a few hours a day for several weeks or while you sleep for 10 to 14 days.

There are many over-the-counter bleaching products, but dentists generally don't recommend them. The one-size-fits-all mouth-guard tray won't fit your mouth as well, and your dentist won't be able to supervise the treatment and possible side effects.