The number of teeth bleaching procedures performed in dentists’ offices has increased by more than 300 percent in the past five years. But while in-office treatment can get your teeth up to 10 shades whiter, it can also set you back as much as $800. Over-the-counter kits promise to lighten for a whole lot less - but which ones really deliver? A national evaluation is to be conducted using the latest products sold in drugstores to find what teeth whitening product really works best. Also to find out which of these kits remove higher degree of surface stain, leaving teeth noticeably whiter, and to test which of these products were easier, better tasting and more effective than others.