The influence of bracket design on moment production during axial rotation

The interaction between the bracket of an axially rotated tooth and arch wire produces a moment. This moment influences tooth movement and rotational control and is itself influenced by bracket width and bracket ligation. Self-ligating spring clip brackets fasten to and interact with arch wires differently than conventionally ligated brackets. An in vitro study with a simulated orthodontic model was undertaken to evaluate the effects of bracket width and ligation technique on the moment production of conventional and self-ligated brackets during axial rotation. Bracket widths ranged from 1.890 mm (0.0744 inch) to 2.809 mm (0.1106 inch). Steel tie, elastomeric, and self-ligating spring clip ligation techniques were used. Empirically, both bracket width and ligation technique significantly effect the moment produced during axial rotation. For the range of bracket widths and types evaluated, ligation technique was found to have a greater influence on moment production than did bracket width. The self-ligated spring clip bracket delivered the least force over the greatest range of axial rotation.