Abstract:Objective To analyze the torque performance of lingual brackets with slots in different directions and the influence pattern of arch wires with different sizes and materials on torque of these lingual brackets. Methods The finite element models of the anterior maxilla lingual brackets with vertical and horizontal slot were constructed, including three kinds of materials (stainless steel, beta-titanium, nickel-titanium) and two sizes of arch wires (0.43 mm×0.56 mm, 0.41 mm×0.56 mm), so as to compare and analyze their mechanical properties after the application of torque load on the left upper central incisors with a rotation angle of ±20°. Results With the increase in elastic modulus of the arch wire, torque moments of lingual brackets with horizontal and vertical slot both increased gradually. Torque performance of lingual brackets was affected more by the sizes and materials of arch wires than the directions of slots. The lingual bracket with vertical slot produced 1-2 times of torque force than that with horizontal slot under the same degree of torque angle. The effect of arch wire sizes was smaller than that of arch wire materials, while the synergistic change in sizes and materials of arch wires had the largest influence on torque performance of lingual brackets. Conclusion The lingual brackets with different slot directions, sizes and materials of arch wires will influence the torque performance of lingual brackets. In clinical application, slot directions of lingual brackets as well as sizes and materials of arch wires should be adjusted properly according to the required torque force.