Teeth Whitening Trays are systems that you can obtain from your dentist. This system includes a custom made tray that is designed to fit the unique contours of your mouth, and a prescription bleaching material that is highly concentrated. With regular use, this system can give you wonderful results. One word of warning; the bleaching solution that is used with the trays is very potent and can cause your teeth or gums to become sensitive. Sometimes the nerve of the tooth can even get irritated when the carbamide peroxide sinks through the enamel into the dentin. The cost of having a tray custom made to fit your mouth can be very expensive.