External root resorption prevalence on adjacent teeth associated with maxillary impacted canines in CBCT images

External root resorption (ERR) is a significant complication associated with impacted maxillary canines that can affect the prognosis of adjacent teeth. This study evaluated the prevalence, anatomical distribution, and risk factors of ERR in teeth adjacent to impacted maxillary canines using cone-beam computed tomography (CBCT).

This retrospective cross-sectional study analyzed CBCT images of 66 patients (81 impacted canines) with maxillary canine impaction. An endodontist and radiologist evaluated impaction characteristics, proximity relationships (≤ 0.5 mm), and ERR presence, location, and severity in adjacent teeth using consensus-based assessment.

ERR was detected in 50 of 243 adjacent teeth (20.58%). Lateral incisors showed significantly higher resorption prevalence (35.80%) compared to central incisors (13.58%) and first premolars (11.11%) (p < 0.001). Physical proximity was strongly associated with resorption occurrence across all tooth types (p < 0.001). Buccal canine positioning significantly increased central incisor resorption risk (p = 0.019). Heat map analysis revealed middle third predominance in central incisors, while lateral incisors showed more distributed patterns between middle and apical thirds. Root development stage and follicle width showed no significant associations with resorption presence.

Physical proximity emerges as the primary determinant of ERR risk in teeth adjacent to impacted maxillary canines. Lateral incisors demonstrate the highest vulnerability, while the buccal positioning of the canine tooth specifically increases central incisor resorption risk. CBCT evaluation with detailed anatomical assessment is essential for comprehensive risk evaluation and treatment planning in maxillary canine impaction cases.