title: Radiographic study of the mandibular retromolar canal: an anatomic structure with clinical importance.
abstract: BACKGROUND
  The retromolar canal is an anatomic structure of the mandible with clinical importance. This canal branches off from the mandibular canal behind the third molar and travels to the retromolar foramen in the retromolar fossa. The retromolar canal might conduct accessory innervation to the mandibular molars or contain an aberrant buccal nerve.
  
  
  METHODS
  Patients referred for panoramic radiography were consecutively enrolled, provided a limited cone-beam computed tomography (CBCT) scan had also been taken in the area of interest. Radiographs were retrospectively screened for the presence of a retromolar canal, and linear measurements (distance to second molar, height, width) were taken.
  
  
  RESULTS
  One hundred twenty-one sides in 100 patients were evaluated (100 unilateral and 21 bilateral cases). A total of 31 retromolar canals were identified with CBCT (25.6%). Only 7 of these canals were also seen on the corresponding panoramic radiographs. The existence of a retromolar canal was not statistically related to gender or side. With regard to the linear measurements, the mean distance from the retromolar canal to the second molar was 15.16 mm (±2.39 mm), the mean height of the canal was 11.34 mm (±2.36 mm), and the mean width was 0.99 mm (±0.31 mm).
  
  
  CONCLUSIONS
  This radiographic study documents a frequency of 25% for the presence of a retromolar canal. The clinician is advised to preserve this anatomic variation when performing surgery in the retromolar area and to consider additional locoregional anesthesia in the case of failed mandibular block anesthesia.
authors.affiliation: Department of Oral Surgery and Stomatology, School of Dental Medicine, University of Bern, Bern, Switzerland. thomas.vonarx@zmk.unibe.ch
authors.forename: Thomas
authors.initials: T
authors.lastname: von Arx
authors.forename: Andrea
authors.initials: A
authors.lastname: Hänni
authors.forename: Pedram
authors.initials: P
authors.lastname: Sendi
authors.forename: Daniel
authors.initials: D
authors.lastname: Buser
authors.forename: Michael M
authors.initials: MM
authors.lastname: Bornstein
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002508:Cephalometry / Q000379:methods; D054893:Cone-Beam Computed Tomography / Q000379:methods; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging* / Q000294:innervation; D008340:Mandibular Nerve / Q000000981:diagnostic imaging; D008875:Middle Aged; D008964:Molar, Third / Q000000981:diagnostic imaging* / Q000294:innervation; D011856:Radiographic Image Enhancement / Q000379:methods; D011862:Radiography, Panoramic / Q000379:methods; D012189:Retrospective Studies; D019237:Tooth Cervix / Q000000981:diagnostic imaging; D014095:Tooth, Impacted / Q000000981:diagnostic imaging; D055815:Young Adult