[Materials technology research on the problem of friction between bracket and arch].

Orthodontic tooth movement along the arch wire is associated with a frictional force between bracket and wire. There is as yet little certainty as to how much force is lost as a result of friction. Therefore a measuring apparatus was used to measure torque in relation to bracket angulation. In all, five types of wire, each of different dimensions were measured in three brackets of differing widths. The results showed significant differences between the types of wire. As the wire dimensions are increased, so likewise are the frictional forces. Bracket with and frictional force bear an inverse relationship to each other. Frictional force increases the greater the surface roughness of the wire.