Efficiency of torque control in customized lingual appliance with different ligatures.

Objectives: To analyze the different torque expression obtained in a customized lingual appliance using archwire of different size and material and different type of ligatures. A threshold parameter of 2Nmm was used to discuss the result as a useful clinical value for torque expression.
Methods: A Home-made typodont has been built and bendy with customized lingual bracket 022x022.
Tested wires: 0.016x0.022 nickel-titanium, 0.0182x0.0182 beta III titanium.
Tested ligatures: Alastik® ligatures, o-ring ligatures, over-tie ligatures.
An extension will be laser-welded to one missing tooth’s bracket in order to apply the forces necessary to study it.
The Zwick/Roell Z0.5 machine to be used to apply forces to the system, using forces from 0N to 1N. For data collection software TestXpert® II.
Torque moment is calculated by multiplying the force applied through the arm. The torque angle is algebraically calculated: ZwickLine® machine measure also the displacement performed by the extension, knowing the displacement and the arm we can derive the sine of the torque angle.
Results: The angulation need to obtain a 2Nmm torque wiht 16x22 NiTi wires were: o-ring: 21,9°, over-tie: 1,7°, Alastik: 14,4°
For the 182x182B-Ti wire: o-ring: 9,1°, over-tie: 5,2°, Alastik: 9,1°.
Conclusions: The use of Alastik ligature created a better torque control for 16x22 NiTi wires when compared to traditional o-ring ligatures. The over-tie was the most efficient. For the 182x182 wire the over-ite ligature is still the most efficient and obtain a good control of torque at 5.2°.