title: Applied anatomy of the lingual nerve: relevance to dental anaesthesia.
abstract: OBJECTIVE
  (1) to classify the external morphology of the lingual nerve and investigate any relationship between its external and internal morphology, (2) to explore the fascicular structure, nerve tissue density and capillary density of the lingual nerve, and (3) to provide an anatomical explanation as to why adverse clinical outcomes more commonly affect the lingual nerve following local dental anaesthesia. Where possible, comparisons were made between the lingual and inferior alveolar nerves.
  
  
  METHODS
  The lingual and inferior alveolar nerves were examined in 23 hemi-sectioned heads macroscopically and microscopically 2mm above the lingula. The lingual nerve was also examined in the regions of the third and second molars. Specimens underwent histological processing and staining with Haematoxylin & Eosin, Masson's Trichrome, anti-GLUT-1 and anti-CD 34.
  
  
  RESULTS
  The lingual nerve became flatter as it traversed through the pterygomandibular space. There was an increase in the connective tissue and a decrease in nerve tissue density along the lingual nerve (p<0.001). At 2mm above the lingula, the lingual nerve was uni-fascicular in 39% of cases, whilst the inferior alveolar nerve consistently had more fascicles (p<0.001). The lingual nerve fascicles had thicker perineurium but the endoneurial vascular density was not significantly different in the two nerves.
  
  
  CONCLUSIONS
  The greater susceptibility of lingual nerve dysfunction during inferior alveolar nerve blocks may be due to its uni-fascicular structure and the thicker perineurium, leading to increased endoneurial pressure and involvement of all axons if oedema or haemorrhage occurs due to trauma.
authors.affiliation: School of Dentistry, The University of Adelaide, Adelaide, SA, Australia.
authors.forename: Vui Leng
authors.initials: VL
authors.lastname: Tan
authors.affiliation: Discipline of Anatomy and Pathology, The University of Adelaide, Adelaide, SA, Australia.
authors.forename: Alice
authors.initials: A
authors.lastname: Andrawos
authors.affiliation: Discipline of Anatomy and Pathology, The University of Adelaide, Adelaide, SA, Australia.
authors.forename: Mounir N
authors.initials: MN
authors.lastname: Ghabriel
authors.affiliation: School of Dentistry, The University of Adelaide, Adelaide, SA, Australia. Electronic address: grant.townsend@adelaide.edu.au.
authors.forename: Grant C
authors.initials: GC
authors.lastname: Townsend
mesh_terms: D000766:Anesthesia, Dental; D002102:Cadaver; D006801:Humans; D008036:Lingual Nerve / Q000033:anatomy & histology*; D013194:Staining and Labeling
keywords: Dental anaesthesia; Inferior alveolar nerve; Lingual nerve; Nerve trauma