After you're finished wearing fixed braces, you need something to keep your teeth from going back to their original position. Retainers are designed to hold teeth in their new locations until all parts of the mouth and jaw have adjusted to the new tooth positions. Retainers may be fixed or removable and made of metal, acrylic, or a combination of the two. One type of retainer, called a tooth positioner, is made of rubber. For severely crowded or rotated teeth, a fixed retainer may be required. Fixed retainers are bonded to the lower teeth and may have to be worn for two years or longer. Retainers must be worn daily as directed by your orthodontist, or teeth may become crooked again. The length of time a retainer must be worn varies with each patient. On average, it's about eighteen months to two years; but some patients may need to wear retainers indefinitely. Contact an orthodontist for more information on retainers.