Abstract: Objective: To investigate the influence of labial bracket position on the resistance center of upper anterior teeth. Methods: The 3D finite element analysis (FEM) models of segment retraction force system with labial brackets placed at different heights were constructed. The arch wire was set as rigid. Retraction force was applied to the anterior teeth (every 0.5mm above the arch wire) and was parallel to the arch wire. When the ratio of the displacement of maxillary incisor edge’s middle point to the apex was close to 1, the bodily movement was considered to occur to the anterior teeth, and the perpendicular distance of center of resistance was recorded. The anteroposterior position of resistance center in the same way was determined. Results: In labial orthodontics, when the distance of maxillary anterior teeth’s brackets to the incisor edge was 5mm, the location of the center of resistance was 16.5mm apical and posterior 13mm to the incisor edge. When the distance was 6mm, the location of center of resistance was 17.5mm apical and posterior 12mm to the incisor edge. When the distance was 4mm, the location of center of resistance was 18mm apical and posterior 13mm to the incisor edge. Conclusion: The positions of resistance center of different labial bracket positions showed little difference.

Key words: Three dimensional finite element analysis , Labial orthodontic treatment, Biomechanics, Center of resistance