Interruption Regions in the White Line: A Novel Panoramic Finding in the Risk Assessment of Mandibular Canal Exposure by Third Molar

Abstract

Introduction: Panoramic markers are the indicators which can be demonstrated in panoramic radiograph to aid in dental diagnosis. Several panoramic markers were developed as diagnostic approach to predict Mandibular Canal (MC) exposure by Impacted Mandibular Third Molar (IMTM). Aim: To evaluate the type and number of panoramic markers in panoramic radiographs. To evaluate presence or abscence of mandibular canal exposure by impacted mandibular third molar from cone beam computed tomography images. To relate the type and number of panoramic marker with the risk of mandibular canal exposure by impacted mandibular third molar. Materials and Methods: The design of this study was a retrospective cross-sectional. A total of 188 panoramic radiographs of IMTMs were analysed initially to determine the type and number of panoramic radiological markers. A panoramic radiological marker would suggest an increased risk of MC exposure by IMTM when there was presence of MC exposure sign from the associated Cone Beam Computed Tomography (CBCT) image. The presence of MC exposure sign in the CBCT image was characterised by a disruption in the radiopaque cortex of MC by IMTM. A modification of the original classification of panoramic markers by Rood and Shehab (1990) was performed and used to determine the type of markers present. Chi-square test was used to analyse the association between the panoramic radiological markers and the MC exposure. Results: Markers such as interruption of the white line posterior to the third molar tooth (OR 2.74, p=0.02) and interruption of the white line anterior to the third molar tooth (OR 2.65, p=0.01) showed increased involvement with the risk of MC exposure. Presentation of more than two markers on the panoramic radiograph was also found to be significantly associated with high risk of the MC exposure, with the odds of 2.14 (p=0.04). Conclusion: Presence of panoramic markers involving the interruption of white line both anterior and posterior to the IMTM poses high involvement of the MC exposure.

Keywords

• cone-beam computed tomography
• mandible
• panoramic radiography
• third molar