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| Inferior alveolar nerve | |
|---|---|
 Distribution of themaxillary andmandibular nerves, and thesubmaxillary ganglion. (Inferior alveolar visible at center left.) | |
 Mandibular division of the trigeminal nerve. (Inferior alveolar labeled at bottom right.) | |
| Details | |
| From | Mandibular nerve |
| To | Mylohyoid, dental,incisive, andmental |
| Innervates | Dental alveolus |
| Identifiers | |
| Latin | nervus alveolaris inferior |
| TA98 | A14.2.01.089 |
| TA2 | 6274 |
| FMA | 53243 |
| Anatomical terms of neuroanatomy | |
Theinferior alveolar nerve (IAN) (also theinferior dental nerve) is asensory[1][contradictory] branch of themandibular nerve (CN V3) (which is itself the third branch of thetrigeminal 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 itsmental nerve).
The inferior alveolar nerve arises from themandibular nerve.[2]: 543
After branching from the mandibular nerve, the inferior alveolar nerve passes posterior to the lateral pterygoid muscle. It issues a branch (themylohyoid nerve)[contradictory] before entering themandibular foramen[2]: 543 to come to pass in themandibular canal within the mandible. Passing through the canal, it issuessensory branches for the molar and second premolar teeth; the branches first form theinferior dental plexus which then gives off small gingival and dental nerves to these teeth themselves.[3]
The nerve terminates distally/anteriorly (near the second lower premolar)[citation needed] within the mandibular canal by splitting into its two terminal branches: themental nerve, and the incisive branch.[1]
The mental nerve emerges from the mandibular canal through themental foramen[1] and provides sensory innervation to thechin and lowerlip.[citation needed]
The incisive branch represents the anterior continuation of the inferior alveolar nerve.[citation needed] It continues to course within the mandible in themandibular incisive canal either as a single nerve or by forming the incisiveplexus. It provides sensory innervation to the lower/mandibular premolar,canine,incisor teeth as well as their associatedgingiva.[1]
The inferior alveolar nerves supply sensation to the lower teeth,[2]: 519 and, via the mental nerve, sensation to thechin and lowerlip.[citation needed]
Themylohyoid nerve is a motor nerve supplying themylohyoid and the anterior belly of thedigastric.[citation needed][contradictory]
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.[4]
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.[5] This can result in a significant reduction in quality of life with functional difficulties and psychological impact.[6]
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] is cited forlingual nerve paresthesia. It is well documented that inferior alveolar nerve injury is more common than lingual nerve injury.[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.[7] 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).[8] 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.[9]
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.[10] 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] Routine preoperative warnings about these injuries should occur before surgery, and represent good practice.[11][12] 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.[13]
During dental procedures, a localnerve block may be applied. Anaesthetic injected near the mandibular foramen to block the inferior alveolar nerve and the nearby lingual nerve (supplying thetongue). This causes loss of sensation on the same side as the block to:
Studies found that oral medications ofNSAIDs taken before the dental procedure increases the efficacy of the anesthesia in patients withirreversible pulpitis.[14]
