There are two different options to undergo professional teeth whitening: in-office treatment and at-home treatment through a dentist. Both options use peroxide-based bleaching agents (carbamide or hydrogen peroxides). With in-office treatment, your dentist will apply a product or solution that contains around 15% to 43% peroxide. It works quickly and the effect lasts longer than an at-home treatment. With at-home treatment, your dentist will make you custom-fit tray filled with a bleaching gel that contains around 3% to 20% peroxide. You will have to place this tray over your teeth for 30 minutes to an hour a day for a few weeks. Both in-office and at-home treatments do not involve any anesthesia.