Bleaching is a noninvasive method of lightening the color of teeth by soaking them with chemical called carbamide peroxide. Impressions are taken of the teeth to be bleached and a thin plastic mouth guard is constructed. A gel containing the bleaching chemical is dispensed into the tray and worn for several hours a day for a period of about two weeks. No one can really predict how much lighter your teeth will become. However bleaching is successful in about 90% of patients. The success rate depends upon the type of stain involved and your compliance. Bleaching can only provide a shift in color from gray to a lighter shade of gray, for example. Bleaching does not lighten artificial materials such as resins, silicates, or porcelains.