Cone Beam CT Evaluation of the Three‐Dimensional Relationship Between Impacted Mandibular Third Molars and the Mandibular Canal

ABSTRACT Introduction Impacted mandibular third molars are often removed, but proximity between mandibular third molar roots and the mandibular canal is clinically important because it may influence surgical planning and the assessment of anatomical relationships before extraction. Cone beam computed tomography (CBCT) enables three‐dimensional assessment of the mandibular canal–root relationship for surgical planning. Methods This retrospective cross‐sectional study was approved by the Ethics Committee of Islamic Azad University, Isfahan (approval no. IR.IAU.KHUISF.REC.1399.0113). Included mandibular third molars were impacted/semi‐impacted with complete root development and radiographic proximity to the canal; inadequate images and cases with anomalies, lesions, fractures, tumors, infection, or other pathology were excluded. Canal position relative to roots (apical, buccal, lingual, inter‐radicular), impaction angulation (vertical, horizontal, mesioangular, distoangular), and canal–root relationship (no contact, cortical contact, penetration) were recorded. Associations were tested using chi‐square/Fisher's exact tests ( α = 0.05). Results In 164 teeth, mesioangular impaction was most common (44.5%), followed by vertical (33.5%), horizontal (20.7%), and distoangular (1.2%). Canal position was most often apical (43.3%), then buccal (27.4%), lingual (23.8%), and between roots (5.5%). Impaction type was not significantly associated with canal position ( p = 0.153) or contact variables (contact type p = 0.328). Among 162 teeth with available contact classification, contact type differed by canal position ( p < 0.001): Penetration was highest with lingual (66.7%) and apical (54.9%) canals, while no contact predominated with buccal canals (48.9%). Conclusion CBCT indicated that apical canal positioning and mesioangular impaction predominated. Canal position, rather than impaction type, showed the strongest association with radiographic penetration and should be considered during preoperative evaluation of mandibular canal–root relationships and surgical planning.