Contact of the incisive canal and upper central incisors causing root resorption after retraction with orthodontic...

To explore risk factors for contact between the incisive canal (IC) and upper central incisors (U1) and to evaluate the relationship between contact and root resorption using cone-beam computer tomography (CBCT).

This retrospective study used CBCT data of 33 patients treated by a senior orthodontist. Anterior teeth were retracted with mini-implants, and CBCT scans were taken before and after retraction. IC height and width, U1 lingual movement, and U1-IC distance and root length decrease were compared between contact and noncontact groups.

Sixteen U1 roots in 11 patients touched the IC. The contact group had lower positioned ICs (2.86 ± 1.10 mm) than the noncontact group (4.07 ± 1.72 mm). The middle of the U1 roots showed more lingual movement to ICs in the contact group (2.30 ± 1.20 mm) than in the noncontact group (1.07 ± 1.16 mm). Right central incisors were closer to the IC than were the left. Root length decreased significantly more in the contact group (2.63 ± 0.93 mm) than in the noncontact group (1.14 ± 0.83 mm).

There is a risk for the U1 root to contact the IC during anterior retraction when the IC is lower positioned. This contact might cause external apical root resorption.