Impact of upper central incisor contact with incisive canal on root resorption and retraction efficiency: A retrospective CBCT study

To explore the impact of contact between the upper central incisors' roots and the incisive canal on retraction efficiency and root resorption during extensive orthodontic retraction.

The retrospective study used cone-beam computed tomography (CBCT) data from 65 patients undergoing orthodontic extraction treatment with retraction of incisors (≥3mm) between 2018 and 2023. All eligible cases during this period were consecutively included. CBCT scans were obtained before and after the treatment. The changes in root length (ΔRL), U1/PP, U1-IC distance, horizontal retraction distance of the incisal edge (HRD), and horizontal retraction distance of the alveolar ridge crest (HRD') were compared between the contact and non-contact groups.

Among the 65 included patients, approximately 30.77% of the cases exhibited contact between the upper central incisor roots and the incisive canal. The initial upper incisor to palatal plane angle (U1/PP) in the non-contact group was significantly greater than that in the contact group. However, the change of upper incisor to palatal plane angle (ΔU1/PP) following treatment showed no statistically significant difference between the two groups. The amount of root resorption in the contact group was significantly greater than that in the non-contact group, but there were no significant differences in HRD and HRD' between the two groups.

Contact between the roots of the maxillary incisors and the incisive canal was associated with increased root resorption. Patients with smaller initial U1/PP values were more likely to experience such contact. Although retraction of the incisal edges and the alveolar ridge crest was not significantly affected, this type of contact may represent a biological compromise and should be avoided when possible.