Abstract: Objective: To discover the mechanical property and the change rule about the tooth rotation of the passive double colpus of self-ligating system by using 3-D finite element analysis. Method: Damon Q bracket was selected as the objective. 3-D finite element models of the Damon Q and the wire with different size were established. Researchers assembled the models, did the mesh division, set up parameter and loaded power. After that, data were analyzed and graphs were drawn. Result: When assembled a single wire, the torsional torque value increased with the size of wire. In the double wire group, the torsional torque value increased with the size of assistant wire under the same main arch wire; when the assistant wire was immutable, there showed a positive correlation between the torsional torque value and the size of main arch wire. When using the same size of wire in the main colpus, torsional torque value of the single wire group was much less than the double wire group. Conclusion: The torsional property of the double wire group was much higher than the single wire group. Logical use of the assistant-horizontal colpus would be good for correcting the rotated teeth.

Key words: DamonQ, bracket, Torsion, The, technology, of, double, wire