Finally, fixed retainers may be an option for some people, especially on the lower front teeth. As their name implies, they aren't removable by the wearer — but they aren't visible either. Like lingual braces, this system uses a wire which is bonded to the tongue side of the teeth. It may remain in place for months, or longer. This type of retainer is sometimes recommended when there's a high risk that teeth could revert to their former position.