Incisive canal remodelling following maximum anterior retraction reduces apical root resorption

The objectives were to visualize the incisive canal (IC) remodelling following maximum incisor retraction and to evaluate its impact on canal-invasion-associated apical root resorption.

Pre- and post-treatment CBCT images of 34 adult orthodontic patients (age 18-47 years) with a large amount of maxillary incisor retraction (>4 mm) using temporary anchorage devices (TADs) were retrospectively evaluated. Maxillary regional superimpositions and 3D models of the IC along with central incisors were used to measure the changes in IC dimension, IC invasion by the roots and IC remodelling. In addition, the association of the amount of apical root resorption with the root-IC relationship and IC remodelling were evaluated.

IC invasion by the incisor roots following maximum retraction was seen in 53% (18 out of 34) of the cases. IC with larger volume and area showed more invasions compared with those with smaller volume and area (P < .01). The amount of root resorption was significantly higher with IC invasion than without invasion (2.39 mm vs 0.82 mm, P < .0001). IC remodelling following maximum retraction was seen in 24% of the subjects. IC remodelling group demonstrated less apical root resorption than the non-remodelling group (0.98 mm vs 3.27 mm, P < .0001).

IC with larger volume and surface area before treatment were more likely to show canal invasion by the incisor roots after maximum retraction. IC invasion resulted in apical root resorption. However, approximately one-fourth of cases showed remodelling of the IC, which reduced the amount of root resorption.