[Incisor torque control with fixed appliance].
OBJECTIVE
To evaluate the properties of orthodontic rectangular arch wires in torsion.


METHODS
To measure and analyze the torsional moments and angles of 0.46 mm x 0.63 mm rectangular orthodontic arch wires in single 0.022 inch bracket of the maxillary central incisor with a torsion measurement apparatus.


RESULTS
(1) The torsional stiffness of stainless steel arch wires, Chinese nitinol arch wires, 7.0 mm vertical loop arch wires, 3.0 mm and 6.0 mm horizontal loop arch wires is 4.909, 1.325, 4.137, 3.448 and 3.024 Nmm per degree, respectively. (2) The arch wires will be twisted 19.143, 36.832, 19.851, 21.812 and 22.418 degrees; respectively to obtain optimal force. (3) Vertical and horizontal loop decreased the torsional stiffness of the rectangular stainless steel arch wire.


CONCLUSIONS
The straight rectangular stainless steel arch wire is not well suitable for the torque control of the incisor. Loop design in arch wire is capable of decreasing torsional stiffness. The horizontal loop is more effective than vertical loop.
Bai
Ding
D
Department of Orthodontics, West China School of Stomatology, Sichuan University, Chengdu 610041, China. baiding@mail.sc.cninfo.net
Gu
Min
M
Zhang
Jian
J
D006801:Humans; D007180:Incisor; D016382:Orthodontic Appliance Design; D009969:Orthodontic Wires; D013193:Stainless Steel; D019415:Torque
D013193:Stainless Steel