Effects of composition and cross section on the elastic properties of orthodontic wires.

General formulas for wire properties have been derived. These enable comparisons among conventional orthodontic alloys and latest archwire materials. For six common archwire sizes, physical property considerations indicate that Ni-Ti makes the most active "leveling" archwire, the B-Ti is a superior intermediate archwire where flexibility is required, and that S.S. and Co-Cr are the wires of choice for finishing and other applications where stability of form is required. These conclusions are based on the current understanding of equivalent force systems and the mechanical properties of each general classification. Whether these wires or some others are used in future patient care will depend on an uncertain and gloomy economic forecast. The present viewpoint is that the greatest needs are the formulation of empirical equations that better describe the action of triple-stranded archwire in bending and more accurate physical property data for all wires in both the tensile and the torsional states. Such additional information could be very useful to the practitioner in choosing the optimal archwire under changing conditions of cost and availability.