title: Panoramic radiography and cone-beam computed tomography findings in preoperative examination of impacted mandibular third molars.
abstract: BACKGROUND
  Preoperative radiographic examination of impacted mandibular third molars (IMTM) is essential to prevent inferior alveolar nerve injury during extraction. The purpose of this study was to evaluate the correlation between cone-beam computed tomography (CBCT) and digital panoramic radiography (DPR) findings in preoperative examination of IMTM.
  
  
  METHODS
  This retrospective study included 298 teeth in 191 individuals. The relationship between the inferior alveolar canal (IAC) and the IMTM (buccal, lingual, interradicular or inferior), the position of the IMTM with respect to the IAC (contact, no contact), the morphologic shape of the mandible in the IMTM region (round, lingual extended, lingual concave), the type of IMTM (vertical, horizontal or angular) and the number of roots of the IMTM were evaluated on CBCT images. DPR images were evaluated for the number of roots of the IMTM and for the most common radiographic findings indicating a relationship between the IAC and the IMTM (darkening of the roots, diversion of the IAC, narrowing of the IAC and interruption of the white line). Data were statistically analyzed with Cramer V coefficient, Kappa statistic, chi-square and Fisher's exact test.
  
  
  RESULTS
  There was a significant difference in number of roots detected on DPR versus CBCT images. There was a significant association between the type of IMTM and the morphologic shape of the mandible on CBCT images. Darkening of the roots and interruption of the white line on DPR images were significantly associated with the presence of contact between the IMTM and the IAC on CBCT images.
  
  
  CONCLUSIONS
  Panoramic radiography is inadequate, whereas CBCT is useful to detect multiple roots of IMTM. When darkening of the roots and interruption of the white line are observed on panoramic images, there is increased likelihood of contact between the IMTM and the IAC. CBCT is required in these cases.
authors.affiliation: Department of Dentomaxillofacial Radiology, Gazi University Faculty of Dentistry, 82, Sok No: 4 06510, Emek-Ankara, Turkey. drilkaypeker@gmail.com.
authors.forename: Ilkay
authors.initials: I
authors.lastname: Peker
authors.forename: Cigdem
authors.initials: C
authors.lastname: Sarikir
authors.forename: Meryem Toraman
authors.initials: MT
authors.lastname: Alkurt
authors.forename: Zeynep Fatma
authors.initials: ZF
authors.lastname: Zor
mesh_terms: D000328:Adult; D000539:Alveolar Process / Q000000981:diagnostic imaging / Q000294:innervation; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging* / Q000294:innervation; D008340:Mandibular Nerve / Q000000981:diagnostic imaging; D008875:Middle Aged; D008964:Molar, Third / Q000000981:diagnostic imaging*; D011300:Preoperative Care; D019252:Radiography, Dental, Digital / Q000379:methods*; D011862:Radiography, Panoramic / Q000379:methods*; D012189:Retrospective Studies; D014092:Tooth Root / Q000000981:diagnostic imaging; D014095:Tooth, Impacted / Q000145:classification / Q000000981:diagnostic imaging*; D055815:Young Adult