title: Assessment of the shape of the inferior alveolar canal as a marker for increased risk of injury to the inferior alveolar nerve at third molar surgery: a prospective study.
abstract: OBJECTIVE
  Morphologic evaluation of computed tomographic images is an important assessment tool before surgical removal of the lower third molar (LM3). The aim of this study was to ascertain whether the shape of the inferior alveolar canal (IAC) is a reliable predictor for inferior alveolar nerve (IAN) injury during M3 surgery.
  
  
  METHODS
  This prospective study assessed samples with a high risk of IAN injury during M3 surgery based on orthopantomographic examination. The predictor variables were demographic factors (patient's age and gender), anatomic factors (angulation of the tooth), and radiographic factors (cortication status, buccolingual position, shape of the IAC, number of roots, and root shape). The outcome variable was IAN injury. The relation between predictor and outcome variables was analyzed using the Fisher exact test and a logistic regression model.
  
  
  RESULTS
  One hundred sixty-nine LM3s (115 patients) were analyzed. IAN injury was observed in 12 of 115 patients and 13 of 169 LM3s (7.7%). All 13 cases with IAN injury exhibited absence of cortication. A dumb-bell-shaped IAC was considered a useful predictor for IAN injury (sensitivity, 69.2%; specificity, 84.6%). In cases with absence of cortication, logistic regression analysis indicated that a dumb-bell-shaped IAC was closely related to IAN injury (P = .005).
  
  
  CONCLUSIONS
  The cortication status and shape of the IAC are reliable predictors for IAN injury at M3 surgery. Cases exhibiting absence of cortication and a dumb-bell-shaped IAC should be recognized as presenting a high risk of IAN injury at M3 surgery.
authors.affiliation: Clinical Fellow, Department of Oral Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Shiratori
authors.forename: Kenji
authors.initials: K
authors.lastname: Nakamori
authors.forename: Megumi
authors.initials: M
authors.lastname: Ueda
authors.forename: Tomoko
authors.initials: T
authors.lastname: Sonoda
authors.forename: Hironari
authors.initials: H
authors.lastname: Dehari
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D015415:Biomarkers; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008334:Mandible / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000294:innervation / Q000473:pathology; D008340:Mandibular Nerve; D008875:Middle Aged; D008964:Molar, Third / Q000033:anatomy & histology / Q000601:surgery*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012307:Risk Factors; D012737:Sex Factors; D014057:Tomography, X-Ray Computed; D014081:Tooth Extraction / Q000009:adverse effects*; D014092:Tooth Root / Q000033:anatomy & histology; D061221:Trigeminal Nerve Injuries / Q000209:etiology*; D055815:Young Adult
chemical_list: D015415:Biomarkers