Frictional forces in fixed appliances.

The aim of this investigation was to measure the frictional resistance to bodily tooth movement along, a continuous arch wire. A fixed appliance was constructed in vitro to simulate tooth movement in a previously aligned arch. The effect of load, bracket width, slot size, arch wire size, and material were studied. It was found that friction was proportional to applied load and inversely proportional to bracket width. Arch wire dimension and slot size had little effect. Nitinol and TMA (beta-titanium) arch wires produced frictional forces two and five times greater than those of stainless steel.