Inferior alveolar nerve

At a glance

English

Inferior alveolar nerve

Latin (TA2)

Nervus alveolaris inferior

System

Nerve

Region

Head

Side

Paired, left and right

About the inferior alveolar nerve

Known also as the inferior dental nerve, the inferior alveolar nerve is the biggest branch of the posterior division of the mandibular nerve, the third part of the trigeminal nerve. It is mainly sensory, carrying feeling from all the teeth of one half of the lower jaw and, through its mental branch, from the skin of the chin and lip. Before entering the bone it also gives off a small motor branch.

It begins deep to the lateral pterygoid muscle, close to the lingual nerve, which lies in front of it. It descends past the lower border of lateral pterygoid and runs between the ramus of the mandible and the sphenomandibular ligament to reach the mandibular foramen on the inner surface of the ramus, with the inferior alveolar artery and vein. Just before it enters the foramen it gives off the mylohyoid nerve, which runs in a groove on the inner face of the mandible to supply mylohyoid and digastric's anterior belly.

Inside the mandibular canal the nerve runs forwards beneath the roots of the teeth. It gives branches that form an inferior dental plexus, from which fine twigs reach the molar and premolar teeth and their gum. Around the second premolar it divides. The mental nerve leaves through the mental foramen for the chin and lip, while the incisive nerve carries on within the bone to supply the canine and incisors. Occasionally the nerve is split in two, with a second mandibular foramen and a doubled canal on X-rays.

This is the nerve dentists numb most often. The inferior alveolar block places anaesthetic near the mandibular foramen and usually catches the lingual nerve as well, so the lower teeth, the lower lip and chin, and the front of the tongue on that side go numb. Injury can follow removal of lower wisdom teeth whose roots lie close to the canal, implant placement, root canal treatment, deep injections, jaw surgery or fracture. It leaves numbness, tingling or pain of the lip and chin, which may be lasting and can seriously affect daily life. Imaging the tooth's relation to the canal before surgery helps lower the risk.

Course and supply

Arises from

The posterior division of the mandibular nerve (V3) in the infratemporal fossa, deep to lateral pterygoid.

Ends in

Divides in the mandibular canal, near the second premolar, into the mental nerve and the incisive nerve.

Supplies

Sensory to all lower teeth and their gums on one side and, via the mental nerve, to the lip and chin; motor, via the mylohyoid nerve, to mylohyoid and the front belly of digastric.