When you go to your dentist's office to pick up your custom trays, make sure you ask your dentist to show you how to properly load the tray to ensure a comfortable fit. You should also have your dentist show you how to clean and store your trays. Here is a brief refresher on how to load, place, and clean your trays:

• Loading Custom Trays
  Load the tray by expressing one continuous bead of gel approximately halfway up the front of the tray from molar to molar. This should use about 1/2 to 1/3 of a syringe of gel.
• Placing Custom Trays
  Place tray snugly over the teeth and gently press the tray to move the gel into place. Be sure to remove excess gel with a clean finger or soft toothbrush. If the tray is pressed too firmly, the gel will move out of the tray.
• Cleaning Custom Trays
  After whitening is completed, clean the tray with a soft toothbrush and cool tap water, and store it in the tray case.

Be sure to ask your dentist if you have any questions!