Abstract: Objective: To investigate the effects of torque prescription in maxillary anterior lingual brackets on three-dimensional tooth displacement of anterior and posterior teeth. Methods: A three-dimensional finite element model of maxillary dentition with customized lingual orthodontics was established. Two groups of anterior bracket torque prescriptions were set: Group A, central incisors, lateral incisors, and canines were set at +13°, +10°, and +7°, respectively; Group B, the corresponding teeth were set at +20°, +13°, and +9°, respectively. Without traction forces, the initial tooth displacement in both groups was observed. Results: After the engagement of the 0.017×0.025-inch archwire, the anterior teeth in both groups exhibited crown labial inclination with an intrusive tendency, while the posterior teeth generally showed crown lingual inclination, intrusion, and mesial displacement. The degree of lingual inclination increased from the second premolar to the second molar. Notably, the second molar exhibited a specific displacement trend: palatal cusp intrusion and buccal cusp extrusion. Except for a slight decrease in the crown labial displacement of the canines in Group B, all other tooth displacements in Group B were greater than those in Group A. Conclusions: Presetting crown labial torque in anterior brackets improves anterior torque control, while caution is required to prevent side effects in the posterior region, such as crown lingual inclination and buccal cusp extrusion (especially in the second molars), as well as to maintain the posterior arch width for effective torque expression in the canine region.

Key words: lingual orthodontics, torque control, posterior arch width, finite element analysis