Stress-relaxation testing. Part II: Comparison of bending profiles, microstructures, microhardnesses, and surface characteristics of several wrought wires

Abstract

1 h d 1 l’t t e enta I era ure fails to provide the profession with a thorough understanding of the wrought wires used as clasp materials in dentistry. All information currently available has largely been obtained through the use of tensile testing. In tensile testing, the atoms within the alloy are subjected to tensile stresses at a constant rate of loading. This is not representative of the type of stress present in clasp arms during clinical use. Since clasp arms are required to undergo repeated bending, both tensile and compressive stresses are developed within the material. The extent and rate of any clasp deflection vary. To provide data which can be analyzed to obtain results which can be applied to clinical situations, it is imperative that the test methods approach the conditions present during clinical function as much as possible. During stress-relaxation testing, the test specimen is deflected by the instrument and released. The resiliency of the material returns the test specimen to its original position in the same manner as a clasp arm, after it has passed beyond the curvature of the tooth. As the clasp is deflected, both the tensile and compressive stresses