Retainers are custom-made devices worn after orthodontic treatment, such as braces or Invisalign, to keep your teeth in their new, corrected positions and to prevent them from shifting or becoming crooked. They are essential for preventing your teeth from shifting back to their original alignment. There are two main types of retainers: removable (such as clear plastic or wire retainers) and fixed (permanent retainers bonded to the back of your teeth). Retainers are typically worn full-time for a few months after treatment, then gradually reduced to nighttime wear as directed by your dentist or orthodontist.