The inferior alveolar nerve (IAN) (also the inferior dental nerve) is a branch of the mandibular nerve, which is itself the third branch of the

trigeminal nerve In neuroanatomy, the trigeminal nerve ( lit. ''triplet'' nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and chewin ...

. The inferior alveolar nerves supply sensation to the lower teeth.

Structure

The inferior alveolar nerve is a branch of the mandibular nerve. After branching from the mandibular nerve, the inferior alveolar nerve travels behind the lateral pterygoid muscle. It gives off a branch, the

mylohyoid nerve The mylohyoid nerve (or nerve to mylohyoid) is a nerve of the head. It is a branch of the inferior alveolar nerve. It supplies the mylohyoid muscle, and the Anterior belly of digastric, anterior belly of the digastric muscle. It may also supply m ...

, and then enters the

mandibular foramen The mandibular foramen is an opening on the internal surface of the ramus of the mandible. It allows for divisions of the mandibular nerve and blood vessels to pass through. Structure The mandibular foramen is an opening on the internal surfa ...

. While in the

mandibular canal In human anatomy, the mandibular canal is a canal within the mandible that contains the inferior alveolar nerve, inferior alveolar artery, and inferior alveolar vein. It runs obliquely downward and forward in the ramus, and then horizontally f ...

within the mandible, it supplies the lower teeth (molars and second premolar) with sensory branches that form into the

inferior dental plexus The inferior dental plexus is a nerve plexus which supplies the lower jaw. It is branches off of the inferior alveolar nerve and functions as innervation to the mandibular molars, first bicuspid, and part of the second bicuspid. The inferior denta ...

and give off small gingival and dental nerves to the teeth.

Anterior Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

ly, the nerve gives off the

mental nerve The mental nerve is a sensory nerve of the face. It is a branch of the posterior trunk of the inferior alveolar nerve, itself a branch of the mandibular nerve (CN V3), itself a branch of the trigeminal nerve (CN V). It provides sensation to the f ...

at about the level of the mandibular 2nd premolars, which exits the mandible via the

mental foramen The mental foramen is one of two foramina (openings) located on the anterior surface of the mandible. It is part of the mandibular canal. It transmits the terminal branches of the inferior alveolar nerve and the mental vessels. Structure The m ...

and supplies sensory branches to the chin and lower

lip The lips are the visible body part at the mouth of many animals, including humans. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech. Human lips are a tactile sensory organ, and can be ...

. The inferior alveolar nerve continues anteriorly as the mandibular incisive nerve to innervate the mandibular

canines Canine may refer to: Zoology and anatomy * a dog-like Canid animal in the subfamily Caninae ** ''Canis'', a genus including dogs, wolves, coyotes, and jackals ** Dog, the domestic dog * Canine tooth, in mammalian oral anatomy People with the surn ...

and

incisors Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wh ...

Variation

Rarely, a bifid inferior alveolar nerve may be present, in which case a second mandibular foramen, more inferiorly placed, exists and can be detected by noting a doubled mandibular canal on a radiograph. Mandibular nerve 1

Function

The Inferior Alveolar nerves supply sensation to the lower teeth, and, via the mental nerve, sensation to the chin and lower

. The

is a motor nerve supplying the mylohyoid and the anterior belly of the

digastric The digastric muscle (also digastricus) (named ''digastric'' as it has two 'bellies') is a small muscle located under the jaw. The term "digastric muscle" refers to this specific muscle. However, other muscles that have two separate muscle belli ...

Clinical significance

Injury

Inferior nerve injury most commonly occurs during surgery including wisdom tooth, dental implant placement in the mandible, root canal treatment where tooth roots are close to the nerve canal in the mandible, deep dental local anaesthetic injections or orthognathic surgery. Trauma and related mandibular fractures are also often related to inferior alveolar nerve injuries. Trigeminal sensory nerve injuries are associated with numbness, pain, altered sensation and usually a combination of all three. This can result in a significant reduction in quality of life with functional difficulties and psychological impact<. The risk associated with wisdom tooth surgery is commonly accepted to be 2% temporary and 0.2% permanent. However, this risk assessment is not concrete as the same source is cited for lingual nerve paresthesia. It is well documented that inferior alveolar nerve injury is more common than lingual nerve injury. The percentage of injury varies significantly in different studies. Furthermore, many factors affect the incidence of nerve injury. For example, the incidence of nerve injury in teens removing third molars is much lower than the incidence in patients 25 and older. This risk increases 10 fold if the tooth is close to the inferior dental canal containing the inferior alveolar nerve (as judged on a dental radiograph). These high risk wisdom teeth can be further assessed using cone beam CT imaging to assess and plan surgery to minimise nerve injury by careful extraction or undertaking a coronectomy procedure in healthy patients with healthy teeth. The risk of nerve injury in relation to mandibular dental implants is not known but it is a recognised risk requiring the patient to be warned. If an injury occurs urgent treatment is required. The risk nerve injury in relation deep dental injections has a risk of injury in approximately 1:14,000 with 25% of these remaining persistent. Routine preoperative warnings about these injuries should occur before surgery, and represent good practice. Inferior alveolar nerve injury secondary to orthodontic treatment is also emerging in the literature in the recent years as a rare complication and manifested as anesthesia, parenthesis, or combination of both; however full recovery was achieved in all of the reported cases when proper management was applied.

Anesthesia

During dental procedures, a local

nerve block Nerve block or regional nerve blockade is any deliberate interruption of signals traveling along a nerve, often for the purpose of pain relief. Local anesthetic nerve block (sometimes referred to as simply "nerve block") is a short-term block, ...

may be applied. Anaesthetic injected near the mandibular foramen to block the inferior alveolar nerve and the nearby

lingual nerve The lingual nerve carries sensory innervation from the anterior two-thirds of the tongue. It contains fibres from both the mandibular division of the trigeminal nerve (CN V3 ) and from the facial nerve (CN VII). The fibres from the trigeminal nerv ...

(supplying the

tongue The tongue is a muscular organ (anatomy), organ in the mouth of a typical tetrapod. It manipulates food for mastication and swallowing as part of the digestive system, digestive process, and is the primary organ of taste. The tongue's upper surfa ...

). This causes loss of sensation on the same side as the block to: * the

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

(inferior alveolar nerve block) * the

lower lip The lips are the visible body part at the mouth of many animals, including humans. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech. Human lips are a tactile sensory organ, and can be ...

and chin (

block) * front two-thirds of the tongue (

block). Studies found that oral medications of NSAIDs taken before the dental procedure increases the efficacy of the anesthesia in patients with

irreversible pulpitis Pulpitis is inflammation of dental pulp tissue. The pulp contains the blood vessels, the nerves, and connective tissue inside a tooth and provides the tooth’s blood and nutrients. Pulpitis is mainly caused by bacterial infection which itself is ...

Additional images

File:Gray181.png, Mandible of human embryo 95 mm long. Inner aspect. Nuclei of cartilage stippled. File:Gray782 updated.png, Mandibular division of trifacial nerve, seen from the middle line. File:Slide9dddd.JPG, Inferior alveolar nerve File:Slide2cec.JPG, Mandibular nerve and bone. Deep dissection. Anterior view. File:Slide7cece.JPG, Infratemporal fossa. Lingual and inferior alveolar nerve. Deep dissection. Anterolateral view

References

External links

* * * () * () {{Authority control Mandibular nerve Mouth