Abstract: Objective: To explore the difference between two kinds of lingual brackets with different colpus when loaded torsion force with three dimensional finite element analysis. Method: Three dimensional finite element models were created which included Incognito^TM and Kurz^7th brackets from A3 to B3, and assembled with ligature wires and wires of different types and materials. The data were analyzed and graphs of the models were drawn. Results: The load of Incognito^TM was 0 when assembled with 0.012 inch wires, and the other models’ deflection curve of two kinds of lingual brackets was similar. When assembled with the same wire, the max load value of Kurz^7th was 10-12 times more than Incognito’s. When assembled with SS, TMA, and NiTi wire, which were the same size but different materials, their max load ratio of two kinds of brackets was 3.3, 1.3, and 1, respectively, and the load deflection curves were the same. When assembled with the wires of the same materials but different size, the load value of brackets increased with increasing size of wires. Conclusion: To correct torsion teeth, Incognito^TM has a limited effect but Kurz^7th seems to be a good choice, and the length, width, and depth of two kinds of colpusall have an influence to the results.

Key words: Kurz^7th, Incognito^TM, Colpus, 3-D finite element