Finally, remember to always carry — and use — a retainer case. You'd be surprised how many retainers end up folded in a napkin and accidentally discarded! Also, don't expose your retainer to excess heat by washing it in very hot water or leaving it on a heater: That can cause the retainer to warp and make it unusable. With proper care and conscientious use, a retainer can help you transition from braces to a permanent, healthy smile.