Mental nerve

At a glance

English

Mental nerve

Latin (TA2)

Nervus mentalis

System

Nerve

Region

Head

Side

Paired, left and right

About the mental nerve

The mental nerve is the terminal sensory branch through which the inferior alveolar nerve reaches the face. The inferior alveolar nerve arises from V3, the mandibular part of the trigeminal nerve, and runs through the mandibular canal. Near the second premolar it divides: one part, the incisive nerve, stays in the bone for the front teeth, while the other, the mental nerve, turns outwards, upwards and backwards through a short channel to leave the bone at the mental foramen.

The mental foramen lies on the outer surface of the mandible, usually below the second premolar or between the two premolars, about halfway between the alveolar margin and the lower border of the jaw in an adult. It opens upwards and backwards, which matters when giving injections. The nerve leaves it under cover of depressor anguli oris, accompanied by the mental artery and vein, and immediately splits beneath that muscle.

Most accounts describe three branches. One runs downwards to the chin's skin, and two run upwards to the skin and lining of the lower lip and to the gum on the lip side of the lower front teeth and premolars. On the face these branches link freely with the marginal mandibular branch of the facial nerve, which supplies the muscles of the lower lip, though the mental nerve itself has no motor function.

Because the foramen is easy to find, the nerve is often blocked with local anaesthetic placed in the soft tissue around it, giving numbness of the lip, chin and the lining of the lip and cheek back to the second premolar, as needed for surgery or for stitching cuts there. The nerve can be injured by dental implants, by surgery near the premolars and by fractures through the foramen, leaving a numb or tingling lip and chin on one side. In people who have lost their teeth the bone wears away, bringing the foramen near the top of the ridge, where a denture can press on the nerve and cause pain.

Course and supply

Arises from

The inferior alveolar nerve in the mandibular canal, near the second premolar; it leaves the bone through the mental foramen.

Ends in

Divides beneath depressor anguli oris into a branch for the chin's skin and branches for the skin and mucosa of the lip below.

Supplies

Sensory to the chin's skin, the skin and lining of the lower lip, and the labial gum of the lower front teeth and premolars.