Mechanical characteristics of various tempers of as-received cobalt-chromium archwires.

The mechanical characteristics of 24 of the 36 wire cross-sectional configurations were investigated in the as-received state from among the 4 tempers of a cobalt-chromium product. After engineering mechanics were used to validate the efficacy of the span combinations, each wire was measured in flexure to determine its elastic modulus and in tension to determine its yield strength, ultimate tensile strength, and ductility. Other combined characteristics were evaluated, including flexibility, resilience, and the yield strength criterion. In these as-received materials the formability sometimes followed expectations, but the flexibility and resilience characteristics were variable and independent of temper. And although the elastic modulus was independent of testing parameters, it was affected by the loss of material at the corners of rectangular wires. Overall, the stiffnesses of cobalt-chromium wires in round configurations were comparable to those of multi- and single-stranded stainless steel wires but were 3 and 6 times greater than the stiffnesses of beta-titanium and nickel-titanium wires, respectively. In the final analysis, these as-received wires do not meet their potential as a variably formable and variably resilient alternative to stainless steel. Perhaps this is why cobalt-chromium wires have never had the impact on the profession that was expected from them several years ago.