The effects of third-order torque and self - Saint Louis University

enters the slot asymmetrically, contacting a rectangular
wire along either a gingival or occlusal edge. An engaged
0.019- x 0.025-inch archwire with zero torque would be
expected to deflect the clip of either bracket. 76 A third-
order rotation of the slot relative to the archwire,
depending upon its sense, could potentially cause more or
less deflection of the clip, thereby affecting the
faciolingual normal forces exerted by the wire and the
accompanying components of the frictional force system.
The Time2 set generated larger frictional forces at +5
degrees than at -5 degrees of torque. When comparing
frictional resistances at +10 degrees and -10 degrees of
torque, both the Time2 and In-Ovation R brackets showed
greater forces at the positive third-order angulation.
This finding might be explained by the asymmetrical nature
of the clip-designs.
The Victory set also produced a larger mean frictional
force at +10 degrees of torque than at -10 degrees. One
possible explanation could be the occlusogingival asymmetry
of the tie-wings of the Victory bracket design (Figure 3-
9); when viewed from a mesiodistal perspective, the
occlusal tie-wing apparently extends farther facially than
the gingival tie-wing, suggesting that the elastomeric
module could have been lying across the wire with more
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