Most retainers are removable, meaning that you take them out when eating, brushing and flossing. For this reason, they are easy to misplace. Many people wrap their retainers in a napkin when eating, then forget about them afterwards and have to spend hundreds of dollars on a new retainer. A good solution is to always carry your retainer case with you and to use it whenever you're not wearing your retainer. For added protection, never leave the case on a table or a bench — always put it immediately in your backpack, purse or pocket.
Your dentist can give you information on how to clean and care for your specific type of retainer. Regardless of the type, you need to make sure you don't sit on, step on or otherwise damage this delicate and expensive piece of equipment.
Your dentist can tell you how long you should keep wearing your retainer. Since the purpose of retainers is to prevent your teeth from shifting back into their original position, they should be worn at least until your jawbone and gums have had time to stabilize around your newly-aligned teeth. Many orthodontists recommend that children and teenagers wear their retainers until their early or mid-20s — until all the permanent teeth have come in and the jaw stops growing.