title: Correlation of darkening of impacted mandibular third molar root on digital panoramic images with cone beam computed tomography findings.
abstract: OBJECTIVE
  Darkening of the lower third molar root on panoramic images is known to indicate an intimate relationship between the root and mandibular canal. The objective of this study was to investigate the anatomical relationship between the third molar root and its surrounding structures that leads to this panoramic finding.
  
  
  METHODS
  Imaging findings of 253 impacted lower third molars examined by both digital panoramic radiography and cone beam CT were reviewed. Panoramic images were evaluated to detect the presence or absence of darkening of the root where the mandibular canal was superimposed. Cone beam CT images were evaluated for the presence or absence of the following two findings: (1) grooving of the root and (2) thinning or perforation of the cortical plate by the root. The correlation between the panoramic and cone beam CT findings was examined using logistic regression analysis.
  
  
  RESULTS
  80 (32%) third molars showed a panoramic finding of darkening of the root. Between cone beam CT findings, cortical thinning or perforation alone was significantly correlated with this panoramic finding (80%, P < 0.001).
  
  
  CONCLUSIONS
  The panoramic finding of mandibular third molar root darkening was considered to reflect cortical thinning or perforation rather than grooving of the root.
authors.affiliation: Oral and Maxillofacial Radiology, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo 113-8549, Japan. weeraya_t@yahoo.com
authors.forename: W
authors.initials: W
authors.lastname: Tantanapornkul
authors.forename: K
authors.initials: K
authors.lastname: Okochi
authors.forename: A
authors.initials: A
authors.lastname: Bhakdinaronk
authors.forename: N
authors.initials: N
authors.lastname: Ohbayashi
authors.forename: T
authors.initials: T
authors.lastname: Kurabayashi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D054893:Cone-Beam Computed Tomography; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging; D008340:Mandibular Nerve / Q000000981:diagnostic imaging*; D008875:Middle Aged; D008964:Molar, Third / Q000000981:diagnostic imaging*; D011300:Preoperative Care / Q000379:methods; D019252:Radiography, Dental, Digital; D011862:Radiography, Panoramic; D014092:Tooth Root / Q000000981:diagnostic imaging*; D014095:Tooth, Impacted / Q000000981:diagnostic imaging*; D055815:Young Adult