Template:Short descriptionTemplate:Multiple issuesTemplate:Infobox nerve The inferior alveolar nerve (IAN) (also the inferior dental nerve) is a sensory<ref name=":1">Template:Cite journal</ref>Template:Contradictory inline branch of the mandibular nerve (CN V3) (which is itself the third branch of the trigeminal nerve (CN V)). The nerve provides sensory innervation to the lower/mandibular teeth and their corresponding gingiva as well as a small area of the face (via its mental nerve).

StructureEdit

OriginEdit

The inferior alveolar nerve arises from the mandibular nerve.<ref name="GRAYS2008" />Template:Rp

CourseEdit

After branching from the mandibular nerve, the inferior alveolar nerve passes posterior to the lateral pterygoid muscle. It issues a branch (the mylohyoid nerve)Template:Contradictory inline before entering the mandibular foramen<ref name="GRAYS2008">Template:Cite book</ref>Template:Rp 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.<ref>Template:Cite journal</ref>

The nerve terminates distally/anteriorly (near the second lower premolar)Template:Citation needed within the mandibular canal by splitting into its two terminal branches: the mental nerve, and the incisive branch.<ref name=":1" />

BranchesEdit

Mental nerveEdit

The mental nerve emerges from the mandibular canal through the mental foramen<ref name=":1" /> and provides sensory innervation to the chin and lower lip.Template:Citation needed

Incisive branchEdit

The incisive branch represents the anterior continuation of the inferior alveolar nerve.Template:Citation needed 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.<ref name=":1" />

DistributionEdit

The inferior alveolar nerves supply sensation to the lower teeth,<ref name="GRAYS2008" />Template:Rp and, via the mental nerve, sensation to the chin and lower lip.Template:Citation needed

The mylohyoid nerve is a motor nerve supplying the mylohyoid and the anterior belly of the digastric.Template:Citation neededTemplate:Contradictory inline

VariationEdit

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.<ref name=":0">Template:Cite book </ref>

File:Mandibular nerve 1.jpg
Inferior alveolar nerve

Clinical significanceEdit

InjuryEdit

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.<ref name="pmid22247929">Template:Cite journal</ref> This can result in a significant reduction in quality of life with functional difficulties and psychological impact.<ref name="pmid24171179">Template:Cite journal</ref>

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 sourceTemplate:Citation needed is cited for lingual nerve paresthesia. It is well documented that inferior alveolar nerve injury is more common than lingual nerve injury.Template:Citation needed 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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).<ref name="pmid24012054">Template:Cite journal</ref> 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.<ref name="pmid22622663">Template:Cite journal</ref>

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.<ref name="pmid22677874">Template:Cite journal</ref> 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.Template:Citation needed Routine preoperative warnings about these injuries should occur before surgery, and represent good practice.<ref name = "RCA_2013">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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. <ref>Template:Cite journal</ref>

AnesthesiaEdit

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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.<ref>Template:Cite journal</ref>

See alsoEdit

Additional imagesEdit

ReferencesEdit

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External linksEdit

Template:Trigeminal nerve Template:Authority control