Structural responses of orthodontic wires in flexure from a proposed alternative to the existing specification test.

To be reaffirmed in 1987 for lack of a ready replacement, the flexural (elastic-bending) test protocol of ADA Specification No. 32 is judged inadequate. The protocol is problematic because of potentials for erroneous use of the theoretical component, incompatible with the flexible titanium alloy and multistrand stainless steel wires marketed subsequent to the preparation of the specification, and obscure to the clinician because it dictates quantifications of mechanical (pertaining to material only) rather than structural properties (including wire shape and size influences). A five-point elastic-bending test is proposed that stimulates wire activation toward engagement of a single, malaligned tooth crown. An experimental study was undertaken to determine values of transverse stiffness and corresponding elastic range for a broad sample of orthodontic wires and in the process to evaluate the proposed alternative test. Reduced test results are presented; comparisons of rankings and ratios from available theoretical developments and other experimental outcomes, including findings from the existing standard test, were completed. The difficulties with the existing protocol are largely eliminated with the alternative test; a test fixture and procedures are relatively straightforward to fabricate and follow, and the structural characteristics quantified are more meaningful to the practitioner.