Inferior alveolar nerve injury
Inferior alveolar nerve injuries are most common iatrogenic post third mandibular molar extraction although they can occur post dental implant or in mandibular fractures. This article is focused on iatrogenic injuries.
The incidence of inferior alveolar nerve injuries after third mandibular molar extraction is reported to be ~7% (range 0.4-13.4%) 1.
Patients may complain of paresthesia to the lower lip and chin 1.
There are radiographic-identifiable features of the mandibular canal (which contains the inferior alveolar nerve) that place the patient at higher risk of inferior alveolar nerve injuries (although there are other. CT/CBCT allows for more accurate delineation of the relationship than OPG.
The proximity of the third mandibular roots to the mandibular canal is a risk factor, with a higher risk of inferior alveolar nerve injury with an intimate relationship 2:
- distant: ≥1 mm between the root tips and the mandibular canal
- close: superimposition of the root tips over the mandibular canal
- intimate (≥1 of the following)
- mandibular canal diversion
- darkening of the root
- root apices deviation
In addition to an intimate relationship, interruption of the white line of the mandibular canal has been shown to be risk factors on OPG 3.
The presence of a close or intimate relationship of the mandibular canal with the third mandibular molar roots on OPG may necessitate further evaluation with CT or cone-beam CT. Factors on the coronal plane that increase the risk of inferior alveolar nerve injury include 1:
- direct contact of the mandibular canal and roots
- buccal or lingual position of the mandibular canal compared to the roots
- teardrop or dumbbell shape to the mandibular canal
- absence of mandibular canal cortication
- 1. Wang D, Lin T, Wang Y, Sun C, Yang L, Jiang H, Cheng J. Radiographic features of anatomic relationship between impacted third molar and inferior alveolar canal on coronal CBCT images: risk factors for nerve injury after tooth extraction. (2018) Archives of medical science : AMS. 14 (3): 532-540. doi:10.5114/aoms.2016.58842 - Pubmed
- 2. Sarikov, Rafael, Juodzbalys, Gintaras. Inferior Alveolar Nerve Injury after Mandibular Third Molar Extraction: a Literature Review. (2014) Journal of Oral & Maxillofacial Research. 5 (4): e1. doi:10.5037/jomr.2014.5401 - Pubmed
- 3. Su N, van Wijk A, Berkhout E, Sanderink G, De Lange J, Wang H, van der Heijden GJMG. Predictive Value of Panoramic Radiography for Injury of Inferior Alveolar Nerve After Mandibular Third Molar Surgery. (2017) Journal of oral and maxillofacial surgery : official journal of the American Association of Oral and Maxillofacial Surgeons. 75 (4): 663-679. doi:10.1016/j.joms.2016.12.013 - Pubmed