title: 3-Dimensional imaging for lower third molars: is there an implication for surgical removal?
abstract: OBJECTIVE
  Surgical removal of impacted third molars may be the most frequent procedure in oral surgery. Damage to the inferior alveolar nerve (IAN) is a typical complication of the procedure, with incidence rates reported at 1% to 22%. The aim of this study was to identify factors that lead to a higher risk of IAN impairment after surgery.
  
  
  METHODS
  In total 515 surgical third molar removals with 3-dimensional (3D) imaging before surgical removal were retrospectively evaluated for IAN impairment, in addition to 3D imaging signs that were supposed predictors for postoperative IAN disturbance. Influence of each predictor was evaluated in univariate and multivariate analyses and reported as odds ratio (OR) and 95% confidence interval (CI).
  
  
  RESULTS
  The overall IAN impairment rate in this study was 9.4%. Univariate analysis showed narrowing of the IAN canal (OR, 4.95; P < .0001), direct contact between the IAN and the root (OR, 5.05; P = .0008), fully formed roots (OR, 4.36; P = .045), an IAN lingual course with (OR, 6.64; P = .0013) and without (OR, 2.72; P = .007) perforation of the cortical plate, and an intraroot (OR, 9.96; P = .003) position of the IAN as predictors of postoperative IAN impairment. Multivariate analysis showed narrowing of the IAN canal (adjusted OR, 3.69; 95% CI, 1.88 to 7.22; P = .0001) and direct contact (adjusted OR, 3.10; 95% CI, 1.15 to 8.33; P = .025) to be the strongest independent predictors.
  
  
  CONCLUSIONS
  Three-dimensional imaging is useful for predicting the risk of postoperative IAN impairment before surgical removal of impacted lower third molars. The low IAN impairment rate seen in this study-compared with similar selected study groups in the literature of the era before 3D imaging-indicates that the availability of 3D information is actually decreasing the risk for IAN impairment after lower third molar removal.
authors.affiliation: Biostatistics Unit, Institute of Social and Preventive Medicine, University Zurich, Zurich, Switzerland.
authors.forename: Gerold
authors.initials: G
authors.lastname: Eyrich
authors.forename: Burkhardt
authors.initials: B
authors.lastname: Seifert
authors.forename: Felix
authors.initials: F
authors.lastname: Matthews
authors.forename: Urs
authors.initials: U
authors.lastname: Matthiessen
authors.forename: Cyrill K
authors.initials: CK
authors.lastname: Heusser
authors.forename: Astrid L
authors.initials: AL
authors.lastname: Kruse
authors.forename: Joachim A
authors.initials: JA
authors.lastname: Obwegeser
authors.forename: Heinz-Theo
authors.initials: HT
authors.lastname: Lübbers
mesh_terms: D005260:Female; D005500:Follow-Up Studies; D005544:Forecasting; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007431:Intraoperative Complications / Q000517:prevention & control; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging* / Q000601:surgery; D008340:Mandibular Nerve / Q000000981:diagnostic imaging; D008964:Molar, Third / Q000000981:diagnostic imaging* / Q000294:innervation / Q000601:surgery; D011183:Postoperative Complications / Q000517:prevention & control; D011862:Radiography, Panoramic / Q000379:methods*; D012189:Retrospective Studies; D012307:Risk Factors; D014081:Tooth Extraction / Q000009:adverse effects; D014092:Tooth Root / Q000000981:diagnostic imaging / Q000294:innervation; D014095:Tooth, Impacted / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D061221:Trigeminal Nerve Injuries