Flexural evaluations of orthodontic wires to date have typically focused on stiffness, range, and/or strength parameters, either as structural characteristics (partially dependent on the wire volume) or mechanical properties (of the wire composition). The A.D.A. Specification No. 32 requires determination of the latter, specifically elastic modulus and yield strength in flexure. The advent of light-force therapies and the newer (titanium alloy, multistrand) wires and the Specification are at odds; e.g., the elastic limits of the highly flexibles, resilient wires often cannot be attained. An alternative """"""""stiffness test"""""""" has been proposed and recently was employed successfully in determinations of stiffness and elastic-range values in flexure for a wide spectrum of wires currently available to the practitioner. In the quantifications of wire properties in flexure, the test protocol ordinarily directs static activation of specimens to gather necessary force-deformation data. This is in contrast to the manner of clinical use of the appliance in which, following engagement in the brackets, the deactivation behavior of the wire governs tooth movement over the between-appointments period. The proposed research would examine the behavior of a sample of wires in controlled activation and deactivation. It is known that clinical engagement (activation) may take the wire locally beyond its elastic limit, and at least one of the newer wires has been shown to exhibit time-dependent tendencies in its response following activation. The alternative test, having a split-anchorage format with supports imposing partial rotational-deformation constraints as brackets do, would be employed. Structural parameters of interest are the slopes (stiffness characteristics) of the activation and deactivation curves. The amplitude of activation will take half of the specimens beyond their elastic limits and a portion of the specimens will be maintained for specific time periods at the activating-force level (to enable potential manifestation of any creep tendency) before deactivation is initiated. Other independent variables designated are wire composition, support (bracket) width, and test half-span (interbracket distance). Appropriate statistical analyses will enable intrasample comparisons and comparisons with pilot alternate-test results.
