Proximity of mandibular third molar root(s) to surrounding cortical bone: cone beam computed tomography (CBCT) and panoramic findings

Purpose: We evaluated the relationship between mandibular third molar roots (M3Ms) and surrounding cortical bone using cone beam computed tomography (CBCT) and panoramic findings. We studied (a) the location of mandibular third molar roots in relation with cortical bone in terms of contact, penetration, and perforation on CBCT; (b) the relationship between characteristics of a root in panoramic findings and the CBCT image (entire and segmentally); and (c) the relationship of the root plane in panoramic findings vs. CBCT. Material and methods: One hundred five teeth with 224 roots of mandibular third molar from 73 patients were evaluated by using cone beam computed tomography and panoramic image. Result: The relationships were assessed using 105 images of impacted M3Ms: 104/105 (99%) showed cortical bone involvement (30.4% penetration and 68.6% perforation). The more apical the segment, the higher the proportion of perforation. Most (79.9%) of the M3M roots involved a lingual cortex with 46.9% penetration and 49.2% perforation. The panoramic signs of segmental root images—viz. clear and blurred—were not associated with cortical penetration or perforation. Panoramic signs of individual root images—in the same and different planes—could be used to predict root plane M3M roots. The same appearance in the panoramic image was significantly related to the same plane of the root in CBCT (p-value 0.048). Conclusion: These findings could contribute to enhanced radiological assessment and surgical planning.