how long should you keep bleach tray in for
Systems that utilize a 10% carbamide peroxide whitening gel and custom-made bleaching trays (the type of system typically dispensed by dentists, and the one referred to on our pages) typically call for: 1  Once-a-day treatments.2  With each session lasting 2 to 4 hours, or possibly over night.he total amount of time that's needed for a case can be reduced by either: 1  Using a higher-concentration whitener. - 2  Most manufactures make their product in a range of concentrations. 3  We've seen carbamide peroxide products ranging from 10 to 44%. 4  Maximizing the length of your treatment sessions.