[The effect of the ligature on the friction between bracket and arch]

The combinations of five different wire materials and six ligatures were analysed with the help of a testing apparatus in order to determine the loss in orthodontic force caused by friction between arch wire and ligature. The bracket was fixed at an angulation of zero degrees with respect to the arch wire. The results of our measurements can be summarized as follows: 1. Friction is determined mostly by the sort of ligature and by the way of ligation and not by the dimensions of the different arch wires. 2. Friction caused by alastics is significantly less than friction caused by steel-ligatures. This can be observed especially if standard-steel wires are used. 3. Frictional forces are astonishingly low if multistrand wires are used. Even the 0.016 x 0.022 Force 9 wire shows little friction. 4. Orthodontic force may even be neutralized if a steel ligature is combined with standard steel wires (0.016 and 0.016 x 0.022). 5. This leads to the proposal that a steel ligature should be retwisted for about 90 to 180 degrees next to the bracket, if orthodontic tooth translation is to be achieved. 6. Using the Unitek Quicksticks causes least friction beneath the alastics.