Contact of the incisive canal and upper central incisors causing root resorption after retraction with orthodontic mini-implants: A CBCT study

Abstract

Objectives: 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). Materials and Methods: 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. Results: Sixteen U1 roots in 11 patients touched the IC. The contact group had lower positioned ICs (2.86 6 1.10 mm) than the noncontact group (4.07 6 1.72 mm). The middle of the U1 roots showed more lingual movement to ICs in the contact group (2.30 6 1.20 mm) than in the noncontact group (1.07 6 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 6 0.93 mm) than in the noncontact group (1.14 6 0.83 mm). Conclusions: 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.