Structural Properties of Single-Strand Orthodontic Wires from a Proposed Alternative Standard Flexure Test

摘要

In 1977, the American Dental Association published Specification No. 32 for orthodontic wires not containing precious metals. A static-flexural-test portion was included within the Specification toward determination of elastic moduli and yield strengths of orthodontic wires. The flexures test has proved inadequate for the newer, more flexible wires, notable when specimen failures occurred before elastic limits were reached. The purpose of this study was to critique an alternative flexure test that could replace the format used in Specification No. 32. The test incorporated transverse activation, split anchorage, and bracket-simulating supports. The new format was designed to be more clinically oriented; sought were two elastic structural properties: transverse stiffness and elastic-limit range. Wires of orthodontic stainless steel and two titanium alloys were tested and the effects of cross-sectional shape and size, test-span length, and support width were included and controlled to determine their influence on the two dependent variables. Stiffness and elastic-range values for each of the 288 test specimens were determined analytically from the force-deflection data and evaluated statistically through analysis-of-variance procedures.