A Lingual Arch is an orthodontic device which connects two molars in the upper or lower dental arch. When it is on the upper teeth, it is known as a Transpalatal Arch (TPA). On the lower teeth, it is known as a Lower Lingual Arch (LLA). It is usually made out of stainless steel.
These devices are often used to maintain space in the jaw and prevent teeth from tipping in unwanted ways. A Lingual Arch can be soldered to the arch wire, or can be removable. It can also be used passively (to hold space open) or actively (to make space or move teeth).