These days, professional teeth whitening gel isn’t just for the dentist’s office anymore. With one visit to the doctor, you can get a professionally fit, custom molded teeth whitening tray that you can use in the comfort of your own home. This tray will let you use stronger teeth whitening gels than are available over the counter in one-size fits all trays. This is because since these trays are custom molded to your teeth, there is less of a chance that the bleaching agent will seep out and be swallowed, irritating your stomach. Stomach irritation from swallowing the bleaching agent is one of the most serious side effects of teeth bleaching. The best professional teeth whitening gel on the market now is the Opalescence Whitening Gel. This gel is the most clinically approved method of whitening your teeth today.