Contiguity between the mandibular canal and the mandibular third molar in panoramic tomography compared with cone beam computed tomography: a topographic analysis

Objectives: The aim of the present study was to evaluate the topographic relationship between mandibular third molars and the mandibular canal in panoramic tomography and cone beam computed tomography (CBCT). Method and materials: Records of all patients visiting for removal of a mandibular third molar between January 2014 and December 2015 were evaluated retrospectively. In panoramic tomography, the relationship of the roots to the mandibular canal was diagnosed according to the literature. In CBCT scans, the panoramic plane was rebuilt and orthogonal images to that plane were analyzed. Results: A total of 56 mandibular third molars were eligible for the study. Superimposition of tooth apex and mandibular canal (Class I) was similarly often found in both radiographic techniques (P = .22). In contrast, contact of tooth apex and mandibular canal (Class II) was significantly more often seen in CBCT scans than in panoramic tomography (P = .039). No contact of tooth apex and mandibular canal (Class III) was similarly often seen in both radiographic techniques (P = .59). Contact of tooth apex and the mandibular canal (Class II) was significantly more often verified by CBCT imaging than was assumed in panoramic tomography. Conclusions: Preoperative CBCT may be helpful in Class II cases for verification of the topographic relationship between the mandibular canal and mandibular third molars. Keywords: cone beam computed tomography, mandibular canal, mandibular third molar