Frictional characteristics of composite orthodontic archwires against stainless steel and ceramic brackets in the passive and active configurations.

The frictional characteristics of prototype composite archwires were investigated. The resistance to sliding was measured in the dry state for wires with three different volume fractions of fiber reinforcement against stainless steel, polycrystalline alumina, and single crystal alumina orthodontic brackets. Each archwire and bracket combination was tested at 34 degrees C with twelve different normal forces (from 0-400 g) and six different angulations (from 0 degrees -12.5 degrees ). The kinetic coefficients of friction were determined from the slopes of linear regressions through plots of the resistance to sliding versus normal force data. The y-intercepts of these regressions were also evaluated as indicators of the binding magnitude. The tested archwire samples were examined for wear using a scanning electron microscope. A fully factorial model analysis-of-variance showed no significant differences in the frictional coefficients for changes in bracket material, reinforcement level, or angulation. Highly significant differences were observed in the y-intercepts for changes in the reinforcement level and angulation. Highly significant, positive, and linear correlations between the y-intercepts and angulations were also established. Abrasive wear of the composite surface was observed at the archwire-bracket interface, particularly at higher normal forces and angulations. Relative to other frictional studies of metallic archwire materials, the composite archwires had higher kinetic coefficients of friction than stainless steel but lower coefficients than either nickel titanium or beta-titanium archwires against all bracket materials tested. Copyright 1998 Kluwer Academic Publishers