Inferior alveolar nerve

The inferior alveolar nerve arises from the mandibular nerve.{{rp|543}}

After branching from the mandibular nerve, the inferior alveolar nerve passes posterior to the lateral pterygoid muscle. It issues a branch (the mylohyoid nerve){{Contradictory inline|reason=One source states the IAC to be a sensory nerve rather than a mixed nerve, while another appears to claim that it emits a motor (mylohyoid) branch.|date=July 2023}} before entering the mandibular foramen{{cite book |title=Gray's Anatomy |date=2008 |publisher=Churchill Livingstone/Elsevier |isbn=978-0-8089-2371-8 |veditors=Standring S, Borley NR |edition=40th |location=Edinburgh |pages= |display-editors=etal}}{{rp|543}} to come to pass in the mandibular canal within the mandible. Passing through the canal, it issues sensory branches for the molar and second premolar teeth; the branches first form the inferior dental plexus which then gives off small gingival and dental nerves to these teeth themselves.{{cite journal | vauthors = Wolf KT, Brokaw EJ, Bell A, Joy A | title = Variant Inferior Alveolar Nerves and Implications for Local Anesthesia | journal = Anesthesia Progress | volume = 63 | issue = 2 | pages = 84–90 | date = 2016-06-01 | pmid = 27269666 | pmc = 4896047 | doi = 10.2344/0003-3006-63.2.84 }}

The nerve terminates distally/anteriorly (near the second lower premolar){{Citation needed|date=July 2023}} within the mandibular canal by splitting into its two terminal branches: the mental nerve, and the incisive branch.

The mental nerve emerges from the mandibular canal through the mental foramen and provides sensory innervation to the chin and lower lip.{{Citation needed|date=July 2023}}

The incisive branch represents the anterior continuation of the inferior alveolar nerve.{{Citation needed|date=July 2023}} It continues to course within the mandible in the mandibular incisive canal either as a single nerve or by forming the incisive plexus. It provides sensory innervation to the lower/mandibular premolar, canine, incisor teeth as well as their associated gingiva.

The inferior alveolar nerves supply sensation to the lower teeth,{{rp|519}} and, via the mental nerve, sensation to the chin and lower lip.{{Citation needed|date=July 2023}}

The mylohyoid nerve is a motor nerve supplying the mylohyoid and the anterior belly of the digastric.{{Citation needed|date=July 2023}}{{Contradictory inline|reason=One source states the IAC to be a sensory nerve rather than a mixed nerve, while another appears to claim that it emits a motor (mylohyoid) branch.|date=July 2023}}

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.{{cite book | vauthors = Fehrenbach MJ, Herring SW | title = Illustrated Anatomy of the Head and Neck | edition = 4th | location = Philadelphia, PA | publisher = Saunders | date = 2011 | pages = 59 }}

File:Mandibular nerve 1.jpg

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.{{cite journal | vauthors = Renton T, Yilmaz Z | title = Profiling of patients presenting with posttraumatic neuropathy of the trigeminal nerve | journal = Journal of Orofacial Pain | volume = 25 | issue = 4 | pages = 333–344 | date = 2011 | pmid = 22247929 | doi = }} This can result in a significant reduction in quality of life with functional difficulties and psychological impact.{{cite journal | vauthors = Smith JG, Elias LA, Yilmaz Z, Barker S, Shah K, Shah S, Renton T | title = The psychosocial and affective burden of posttraumatic neuropathy following injuries to the trigeminal nerve | journal = Journal of Orofacial Pain | volume = 27 | issue = 4 | pages = 293–303 | date = 2013 | pmid = 24171179 | doi = 10.11607/jop.1056 | doi-access = free }}

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{{Citation needed|date=September 2015}} is cited for lingual nerve paresthesia. It is well documented that inferior alveolar nerve injury is more common than lingual nerve injury.{{Citation needed|date=September 2015}} 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.{{cite web |url=http://www.rcseng.ac.uk/patients/recovering-from-surgery/wisdom-teeth-extraction |title = Recovering from Surgery | publisher = Royal College of Surgeons}} 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).{{cite journal | vauthors = Selvi F, Dodson TB, Nattestad A, Robertson K, Tolstunov L | title = Factors that are associated with injury to the inferior alveolar nerve in high-risk patients after removal of third molars | journal = The British Journal of Oral & Maxillofacial Surgery | volume = 51 | issue = 8 | pages = 868–873 | date = December 2013 | pmid = 24012054 | doi = 10.1016/j.bjoms.2013.08.007 }} 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.{{cite journal | vauthors = Long H, Zhou Y, Liao L, Pyakurel U, Wang Y, Lai W | title = Coronectomy vs. total removal for third molar extraction: a systematic review | journal = Journal of Dental Research | volume = 91 | issue = 7 | pages = 659–665 | date = July 2012 | pmid = 22622663 | doi = 10.1177/0022034512449346 | s2cid = 21579439 }}

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.{{cite journal | vauthors = Renton T, Dawood A, Shah A, Searson L, Yilmaz Z | title = Post-implant neuropathy of the trigeminal nerve. A case series | journal = British Dental Journal | volume = 212 | issue = 11 | pages = E17 | date = June 2012 | pmid = 22677874 | doi = 10.1038/sj.bdj.2012.497 | s2cid = 21328385 | doi-access = free }} 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.{{Citation needed|date=November 2014}} Routine preoperative warnings about these injuries should occur before surgery, and represent good practice.{{cite web |url=http://www.rcoa.ac.uk/system/files/PI-Risk12_1.pdf |title=Nerve Damage Associated with Peripheral Nerve Block | work = Information for patients | publisher = The Royal College of Anaesthetists | date = 2013 |access-date=2014-04-15 |url-status=dead |archive-url=https://web.archive.org/web/20140416191944/http://www.rcoa.ac.uk/system/files/PI-Risk12_1.pdf |archive-date=2014-04-16 }}{{cite web | vauthors = Tidy G | veditors = Bonsall A | date = 27 February 2018 |url=http://www.patient.co.uk/health/anaesthesia-explained|title=Anaesthesia (UK) - Local and General anaesthesia information | work=Patient | publisher = Egton Medical Information Systems Limited }} 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, paresthesia, or combination of both; however full recovery was achieved in all of the reported cases when proper management was applied. {{Cite journal |last1=AlAli |first1=Ahmad M. |last2=AlAnzi |first2=Talal H. |date=2021-01-01 |title=Inferior alveolar nerve damage secondary to orthodontic treatment: A systematic scoping review |url=https://content.iospress.com/articles/international-journal-of-risk-and-safety-in-medicine/jrs200098 |journal=International Journal of Risk & Safety in Medicine |language=en |volume=32 |issue=3 |pages=175–191 |doi=10.3233/JRS-200098 |pmid=33579879 |s2cid=231910002 |issn=0924-6479|url-access=subscription }}

{{main|Inferior alveolar nerve anaesthesia}}

During dental procedures, a local nerve block may be applied. Anaesthetic injected near the mandibular foramen to block the inferior alveolar nerve and the nearby lingual nerve (supplying the tongue). This causes loss of sensation on the same side as the block to:

• the teeth (inferior alveolar nerve block)
• the lower lip and chin (mental nerve block)
• front two-thirds of the tongue (lingual nerve block).

Studies found that oral medications of NSAIDs taken before the dental procedure increases the efficacy of the anesthesia in patients with irreversible pulpitis.{{cite journal | vauthors = Shantiaee Y, Javaheri S, Movahhedian A, Eslami S, Dianat O | title = Efficacy of preoperative ibuprofen and meloxicam on the success rate of inferior alveolar nerve block for teeth with irreversible pulpitis | journal = International Dental Journal | volume = 67 | issue = 2 | pages = 85–90 | date = April 2017 | pmid = 27933616 | doi = 10.1111/idj.12272 | pmc = 9376692 | doi-access = free }}

• Alveolar nerve (Dental nerve)

:* Superior alveolar nerve (Superior dental nerve)

::* Anterior superior alveolar nerve (Anterior superior dental nerve)

::* Middle superior alveolar nerve (Middle superior dental nerve)

::* Posterior superior alveolar nerve (Posterior superior dental nerve)

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

{{Reflist}}

• {{SUNYAnatomyFigs|27|03|06}}
• {{LoyolaMedEd|GrossAnatomy/h_n/cn/cn1/cnb3.htm}}
• {{NormanAnatomy|lesson4}} ({{NormanAnatomyFig|mandibularnerve}})
• {{NormanAnatomy|cranialnerves}} ({{NormanAnatomyFig|V}})

{{Trigeminal nerve}}

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Category:Mandibular nerve

Category:Mouth