Proper buccolingual inclination of teeth is essential to esthetics, stability and occlusion in orthodontic treatment. Factors influencing torque in various orthodontic treatments are frequently discussed by clinical orthodontists. Good control of torque can get the normal buccolingual inclination and beautiful curve of the teeth. Clinically, there are many factors affecting the tooth torque control, such as labial surface shape of crown, root-tooth angle, tip and the center height of clinical crown. Besides, preset angle of brackets, adhesive height, texture of the arch wires, and so on, also have effects. In this paper, we will give a comprehensive review on the factors affecting torque expression in three aspects: Anatomical factors of the tooth, brackets and the properties of the archwire, respectively.
