title: The inferior alveolar nerve's loop at the mental foramen and its implications for surgery.
abstract: BACKGROUND
  In this study, the authors aimed to identify and measure the anterior extension of the alveolar loop (aAL) and the caudal extension of the alveolar loop (cAL) of the inferior alveolar nerve by using cone-beam computed tomography (CBCT). They also aimed to provide recommendations for surgery in the anterior mandible.
  
  
  METHODS
  In this retrospective case study of the frequency and extension of aAL and cAL, the authors evaluated 1,384 mandibular sites in 694 CBCT scans of dentate and partly edentulous patients, performed mainly for further diagnosis before removal of the mandibular third molars between January 2009 and February 2013, by using multiplanar reconstructions.
  
  
  RESULTS
  The frequency of aAL was 69.73 percent and of cAL was 100 percent. The mean value for aAL was 1.16 millimeters, with a range of 0.3 to 5.6 mm; the mean value for cAL was 4.11 mm, with a range of 0.25 to 8.87 mm. For aAL, 95.81 percent of the sites showed values of 0 to 3 mm; for cAL, 93.78 percent of the sites showed values of 0.25 to 6 mm. Dentate patients showed statistically significantly higher values for cAL than did partly edentulous patients (P = .043). CBCT resolution had a statistically significant impact on cAL measurements (P = .001), with higher values at higher resolution.
  
  
  CONCLUSIONS
  This study showed a high frequency of and large variations in aAL and cAL. In contrast to panoramic radiography, CBCT has been shown to be a reliable tool for identifying and measuring the AL. Therefore, preoperative diagnosis with CBCT is recommended for planning three-dimensional tasks such as implant placement in the vicinity of the mental foramen.
  
  
  CONCLUSIONS
  Owing to the variability of aAL and cAL measurements, it is difficult to recommend reliable safety margins for surgical procedures such as implant placement, bone harvesting or genioplasty Depending on the indication, the clinician should consider preoperative diagnosis by means of CBCT.
authors.affiliation: Dr. Filo is an assistant dentist, Center of Dental Medicine, Clinic for Oral and Maxillofacial Surgery, University of Zurich.
authors.forename: Katharina
authors.initials: K
authors.lastname: Filo
authors.forename: Thomas
authors.initials: T
authors.lastname: Schneider
authors.forename: Michael C
authors.initials: MC
authors.lastname: Locher
authors.forename: Astrid L
authors.initials: AL
authors.lastname: Kruse
authors.forename: Heinz-Theo
authors.initials: HT
authors.lastname: Lübbers
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059925:Anatomic Landmarks / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery; D002648:Child; D054893:Cone-Beam Computed Tomography; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible / Q000033:anatomy & histology / Q000294:innervation / Q000601:surgery*; D008340:Mandibular Nerve / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000601:surgery; D008875:Middle Aged; D012189:Retrospective Studies; D055815:Young Adult
keywords: Alveolar nerve; computed tomography; dental implants; implants; mandibular nerve; oral and maxillofacial radiology; oral and maxillofacial surgery; oral surgery; risk assessment