Edward Angle favored a non-extraction approach to all cases and space closure mechanics were not normally needed. Later, however, closing loop archwires became part of traditional edgewise mechanics, as described by Tweed.' Each rectangular steel wire typically had four loops - two omega loops and two closing (teardrop) loops - and had to be individually made for each patient. There was a limited range of action before the omega loop came into contact with the molar tube.
Closing loop archwires were flexible, because of the loops, but applied a heavy space closure force in the extraction sites. There was therefore a need for extra tip, rotation control, and torque control during space closure with these mechanics, and this was achieved by placing individual bends in the wire for each tooth. These bends could be selectively removed or reduced later in the treatment.
There were disadvantages to this method of space closure. A lot of wire bending time was needed, and the forces were heavy; sliding mechanics were poor, and the mechanism had only a short range of activation. Closing loop archwires (Fig. 9.7) are therefore not recommended for routine space closure with preadjusted brackets. Occasionally, they may be helpful in closing a small amount of residual space, especially in adults.
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