November’s Tip

Do not memorize, understand – Dr. T. Mulligan

When the reciprocal force for  closing the larger space is  applied at the level of the  bracket, an undesirable  tipping of the teeth– distal and mesial will occur. The force is applied some distance from the Center of resistance – thus creating a moment of the force.

Off-center (tip-back) bend is placed close to the anchor tooth, (“V” pointing occlusally), as a result crowns will move apart first, and roots will move together.  However, the elastic or elastomeric chain will prevent crowns moving apart and the net result is the convergence of the roots. Thus, during the closure of spaces, the root movement will precede the crown movement without tipping.  There is a long arm and the short arm, the long arm points in the direction of the force and the short arm against the direction of the force.  However, these forces cannot express themself well, because the distance is short, and the arch wire is tied to the rest of the teeth. There may be a slight undesirable mesio-lingual and disto-lingual moment, these moments have to be countered with a lingual intra.

As the teeth approximate, the Off-center bend becomes the Center bend, without any intrusive or extrusive forces, only equal and opposite moments.