The effect of Alexander, Gianelly, Roth, and MBT bracket systems on anterior retraction: a 3-dimensional finite...

The aims of this study were to compare the effect of 4 bracket systems including Alexander, Roth, MBT, and Gianelly on upper anterior retraction and to quantify the amount of torque loss ratio in sliding mechanics by help of a 3-dimensional (3D) finite element method.

3D FEM models were constructed in order to simulate anterior incisor retraction in first premolar extraction case. Displacement, stress, and strain on the incisal edge and apex of maxillary central incisor were calculated when 1-, 2-, and 3-N retraction forces were applied. Torque loss ratio was calculated by measuring the displacement of the teeth at crown tip and root apex in all 4 bracket systems on upper central incisor.

Uncontrolled lingual crown tipping of the incisor was observed in all bracket systems. The crown moved lingually by 9.5 μm and the root labially by 4.5 μm in MBT system with 3-N retraction force. The amount of crown movement was 8 μm and the root displacement was 4 μm in Gianelly system with the same retraction force. Torque loss ratio was 1.46 in Alexander and Gianelly with 3-N retraction force. However, the amount of torque loss ratio was 1.47 in MBT and Roth with the same retraction force.

Uncontrolled tipping was the least in Gianelly and was the highest in MBT. The amount of torque loss ratio was the lowest in Gianelly and Alexander systems and the amount of torque loss ratio was the highest in MBT system.