Frictional forces and surface topography of a new ceramic bracket.

The present study was designed to measure the frictional forces between orthodontic wires and a new ceramic bracket and to investigate the differences in the frictional forces with the new and two previously available ceramic brackets. Frictional forces were measured during the sliding of 0.016 x 0.022-inch and 0.017 x 0.022-inch cobalt-chromium alloy wire through three brackets bonded to a simulated tooth. The wires were not ligated into the brackets, so as to eliminate the influences of ligation on the bracket-wire friction. Further, slot surfaces of the three brackets were examined by scanning electron microscope (SEM). The magnitude of frictional forces produced by the new ceramic bracket was significantly less for both the wires than that produced by the two ceramic brackets at 1% level of confidence. The frictional forces with all the brackets exhibited a slight increase as the wire size became larger. The magnitude of frictional forces decreased substantially as the retraction point shifted more cervically. Slot surfaces of the new ceramic bracket were substantially smoother than those surfaces of the two other ceramic brackets. It is shown that refinements of slot surfaces of the ceramic bracket may be effective to reduce friction, although the bracket-wire frictions in this in vitro study were somewhat underestimated because of the lack of ligation of the wire into the bracket.