Panoramic radiography and cone-beam computed tomography findings in preoperative examination of impacted mandibular third molars

Abstract

BackgroundPreoperative 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.MethodsThis 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.ResultsThere 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.ConclusionsPanoramic 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.

Inferior alveolar nerve injury: Correlation between indicators of risk on panoramic radiographs and the incidence of tooth and mandibular canal contact on cone‐beam computed tomography scans in a Western Australian population

“…This resembles the data reported by Tantanapornkul et al., who they studied 142 teeth and determined that the canal was inferior to 64 teeth (45%), lingual to 37 teeth (26%), buccal to 36 teeth (25%), and between the roots of five teeth (4%). In contrast, much of the literature has reported that the canal is most often buccal or lingual to the third molar. It is clear that there is significant anatomical variation in the position of the mandibular canal.…”

“…Darkening, deflection, or narrowing of the roots of a third molar, as well as interruption, diversion, or narrowing of the white lines of the mandibular canal are associated with a higher risk of injury . The most common sign of a close relationship between these two structures has been consistently reported as the interruption of the white line, followed by darkening of the roots …”

Reliability of Panoramic-Radiograph to Determine the Position of Third-Molar from Inferior-Alveolar-Canal

“…It is recommended in this study to use CBCT as secondary diagnostic modality when panoramic radiograph Gomes et al 2008 Panoramic radiograph does not has a high diagnostic accuracy when it is used in the assessment of risk in surgical extractions of lower third molars Tantanapornkul et al 2007Ghaeminia et al 2011 The diagnostic accuracy of CBCT was superior to panoramic radiography in predicting neurovascular bundle exposure following assessment of the relationship of the third molar root tip to the IAC Hasegawa et al 2013 Panoramic findings mostly inconsistent (62.5%) to CBCT findings. Thus, in planning surgical removal of mandibular third molar, panoramic radiography alone does not provide sufficiently reliable images to assess the risk associated with nerve exposure Peker et al 2014 Less accuracy in panoramic radiograph may indicate further preoperative assessment of impacted mandibular third molar with CBCT especially when darkening of the roots and interruption of the white line are observed on panoramic images shows superimposition of the third molar root on the roof of IAC and the presence of root below the roof of the canal. Additional evaluation with CBCT in such cases is important to determine the actual risk associated with the inferior alveolar nerve injury following surgical removal of impacted mandibular third molar.…”

Removal of Mandibular Third Molar Accidently displaced into the Parapharyngeal Space aided by Cone-Beam Computed Tomography: A Case Report

“…Cone-beam computed tomography (CBCT) is a relatively new imaging modality. Compared with the conventional panoramic radiography (PAN), CBCT can reconstruct the three-dimensional images, provides better image of the teeth and their surrounding structures and thus gives the doctors a more detailed insight into the local anatomy of the teeth [5,6]. As a result, assisted with the CBCT images, the displaced IMTM could be located more accurately, and the removal will be expected to reduce the likely injury to the local structures.…”