title: Anterior loop of the inferior alveolar nerve: Averages and prevalence based on CT scans.
abstract: BACKGROUND
  The treatment of edentulous patients by using a complete implant-supported fixed prosthetic with distal extension has been widely studied; success is mainly dependent upon the placement of the distal implants. The location of the inferior alveolar nerve determines implant placement, but the length, prevalence, and symmetry between the left and right side of the anterior loop of the alveolar nerve are unknown.
  
  
  OBJECTIVE
  The purpose of this clinical study was to measure the anterior loop of the inferior alveolar nerve, which determines the placement of distal implants, in a group of 55 Mexican participants. The study expected to ascertain the average length, prevalence, and symmetry between left and right side and any sex differences. To differentiate the inferior alveolar nerve path, a new technique was applied using Hounsfield unit (HU) thresholds. The null hypothesis was that no significant differences would be found between the left and right sides or between men and women for the anterior loop of the inferior alveolar nerve.
  
  
  METHODS
  Fifty-five computed tomography (CT) scans were made (Somatom Sensation 16; Siemens Healthcare) and were visualized with InVesalius software. Anterior loop measurements were made on 3-dimensional surfaces. To determine statistical differences between the left and right side and between the sexes, the t test was used. The interclass correlation coefficient test was also applied to verify the reliability of the measurements.
  
  
  RESULTS
  Ninety percent of participants showed the anterior loop of the inferior alveolar nerve. The length of the anterior loop ranged between 0 and 6.68 mm, with a mean of 2.19 mm. No significant differences were found between the left and right sides or between men and women.
  
  
  CONCLUSIONS
  The mean length for the anterior loop in the sample was 2.19 mm. As the anterior loop length shows a high degree of variability, these findings suggest that a CT scan for each patient is recommended in order to visualize a safety zone before placing implants close to the mental foramen.
authors.affiliation: Resident, Graduate Studies and Research Division, Dental School, National Autonomous University of Mexico, Mexico City, Mexico; and Professor, Central University of Ecuador, Quito, Ecuador. Electronic address: juanpadel_@hotmail.com.
authors.forename: Del Valle Lovato
authors.initials: del VL
authors.lastname: Juan
authors.affiliation: Professor, Graduate Studies and Research Division, Dental School, National Autonomous University of Mexico, Mexico City, Mexico.
authors.forename: Edgar
authors.initials: E
authors.lastname: Grageda
authors.affiliation: Computed Tomography Scan Specialist, Mexico City, Mexico.
authors.forename: Salvador
authors.initials: S
authors.lastname: Gómez Crespo
mesh_terms: D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible; D008340:Mandibular Nerve / Q000002:abnormalities* / Q000000981:diagnostic imaging*; D015995:Prevalence; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods*