A Glossary of Common Orthodontic Terms

Having a hard time understanding your child’s orthodontist? Don’t worry: We’ve cut through the jargon to give you these non-technical definitions of common orthodontic devices and problems.    


Bionator: A removable device used on children whose jaw structure is still developing. Made of metal and plastic, the apparatus uses gentle pressure to redirect a patient’s jaw growth so that the front and back teeth grow at the same rate. The device should be worn at all times, except when eating, brushing your teeth and playing sports.
Headgear: Generic term for a removable device designed to move the back teeth, or to keep them in the present position, while the front teeth are being straightened. For how many hours a day you wear the headgear depends on your orthodontist’s instructions—some patients wear headgear only at night; others wear at all day. You must remove your headgear, however, when eating or brushing your teeth.
Herbst appliance: A splint with tubes and hinges that holds the lower jaw (or mandible) forward to promote growth, while at the same time applying pressure to the upper jaw (or maxilla) in a backwards direction to prevent growth. This device is used to correct large overbites in patients with small lower jaws.
Palatal bar: A thin bar that connects the upper molars by arching across the roof of the mouth (or the palate). The purpose of the device is to rotate the upper molars into their correct position. A palatal bar cannot be removed by the patient, making it an ideal alternative for those who those who refuse to wear their headgear regularly.
Retainer: A device worn after the braces have been removed to ensure that teeth don’t revert to their pre-braces position. Made of wires, clasps and plastic, removable retainers keep teeth stabilized while the bones of the jaw build up around them.


Crowding: Teeth are misaligned because the dental arch is small and/or the teeth are too large. As a result, teeth bunch together and form a crooked smile with dangerous implications. For starters, gums may recede and weaken. Crowding can also lead to impacted teeth (teeth that grow beneath the gumline but never penetrate the surface). In extreme cases, crowding makes biting and chewing exceedingly difficult—resulting in teeth that are unevenly worn.
Cross-bite: The lower teeth overlap the upper teeth. Also known as under-bite, cross-bite can lead to gum loss and uneven wear on teeth.

Open-bite: The upper and lower teeth do not touch, thrusting forward instead. This condition is usually caused by one or more of the following: thumb-sucking; thrusting your tongue against your teeth when you swallow or sleep; abnormal jaw structure; or underdeveloped teeth.
Overbite: The upper teeth overlap the lower teeth. Minimal overbite is normal, however, a deep-bite—in which the lower teeth are completely covered by the upper teeth—is neither normal nor healthy. A deep-bite can contribute to gum loss and lead to excessive wear of the top front teeth.
Spacing: Teeth are missing or small, or the dental arch is very wide, causing significant gaps between the teeth to appear. Can lead to uneven wear on teeth.