Abstract
A new suspensional type testing apparatus was designed to measure the frictional properties between orthodontic wires and brackets and frictional coefficients were obtained under conditions of single contact plane and double contact planes. Findings were compared for various combinations of brackets and wires, including the esthetic FRP wire that we manufactured. This testing equipment can eliminate geometric factors originating from sources other than the material properties. The frictional coefficients measured by the double contact test were larger than the expected value, √<2> times those by single contact test. The frictional coefficient between polycrystalline alumina bracket and FRP wire was larger than that of other combinations. The frictional properties of FRP wire with brackets were similar to those of metal wires except for the polycrystalline alumina bracket. Frictional properties between wires and brackets under clinical conditions could be affected by not only surface characteristics but the geometric relation and orthodontic force.
