[The properties of different orthodontic rectangular arch wires in torsion].
OBJECTIVE
To study the properties of orthodontic rectangular arch wires in torsion.


METHODS
By using the torsion measurement apparatus, torsion moments and angles of four kinds of orthodontic wires (0.46 mm x 0.63 mm and 0.48 mm x 0.63 mm stainless steel wires, and the same size nickel-titanium wires) were tested respectively in a 0.56 mm-slot first maxillary incisor bracket. According to the torsion moments and angles, scatter graphs were drawn to fit the load-deflection curves of four kinds of wires and their linear equations were calculated. According to the equations, the torsion stiffness and the play angles of the wires at 20 N mm correspondingly were calculated.


RESULTS
The torsion stiffness of four kinds of wires were 4.909, 6.417, 1.325 and 1.363 N mn/degrees, the torsion angles of different wires were 19.14 degrees, 15.33 degrees, 36.83 degrees and 35.07 degrees at 20 N mm respectively.


CONCLUSIONS
The torsion stiffness of stainless steel wires was bigger than that of the same cross-section dimensional nickel-titanium wires. The difference of torsion stiffness between two dimensional nickel-titanium wires is smaller, while the difference of torsion stiffness between two stainless steel wires is larger.
Huang
Ning
N
State Key Laboratory of Oral Diseases, Sichuan University, Chengdu 610041, China.
Gu
Min
M
Han
Xiang-Long
XL
Bai
Ding
D
D007180:Incisor; D009532:Nickel; D009969:Orthodontic Wires; D013193:Stainless Steel; D014025:Titanium
C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium