ON MECHANICAL-PROPERTIES OF SQUARE AND RECTANGULAR STAINLESS-STEEL WIRES TESTED IN TORSION

Forty different sizes and types of square and rectangular stainless st eel wires, supplied by five different manufacturers, were tested in to rsion. The study simulated the situation occurring when torque is appl ied to an individual tooth. We used standard brackets with 0.018-inch slot heights, with an interbracket distance of 4 mm. The results show that variation in cross-sectional dimension and edge bevel leads to va riable torsional play (third-order clearance). As an example 0.016 x 0 .022-inch wires have a mean torsional play of as much as 18.5 degrees, with a range of 16.6 degrees to 20.4 degrees. We have shown that when 0.016 x 0.022-inch wires are used, one must apply from 24.6 degrees t o 29.2 degrees of twist to get 20 Nmm of torsional moment. This variat ion is mostly due to a rather wide range in torsional play. As a resul t, the prediction by which a predetermined torsional moment can be del ivered becomes uncertain, The results show that because the working ra nge in torsion of stainless steel wires is somewhat limited, precise d elivery of torsional moment, based on the condition present in the ora l cavity, is difficult. Torsional stiffness varies considerable within the various dimensional groups, this being the result of variation in cross-sectional geometry and material properties.