Background: The present study evaluated the pattern of root migration following coronectomy of the mandibular third molar in terms of distance, degree of direction, and relevant factors related to root migration. Methods: This retrospective study included 50 coronectomies in 44 patients with at least 1-year follow-up. Panoramic radiographs were taken pre-operatively, within 2 weeks after surgery, and at 3, 6, and 12 months post-operatively. Multiple factors are possibly related to root migration, so we analyzed sex, age, tooth, figure of root, residual bone height, and also as Winter’s and Pell& Gregory classification with respect to angulation, class, and position of tooth. Results: Over the first three months after the coronectomies, all retained roots moved and/or changed their root axis. The respective mean distance of retained root migration in the horizontal (C1), coronal (C2), and oblique (C3) direction during the first year post-operatively was 3.14 ± 1.86 mm, 2.42 ± 1.61 mm, and 3.45 ±1.76 mm. The mean (±SD) root axis change was 11.26 ± 5.55 degrees. The significant influencing factors related to root migration were sex, age, and in particular tooth angulation (GEE: P<0.05). The mesio- and horizontal angulation (M, H) group migrated significantly further horizontally forward (C1) over time than the vertical (V) and distoangulation (D) group. The V, D group showed significantly greater coronal migration (C2) (P=0.05) than the M, H group. The V, D group had only mesial rotation. Conclusion: These findings could contribute to evaluation and/or planning for root removal.
