A single horizontal edgewise slot in a standard-width bracket is generally effective in controlling rotations and tipping. Biomechanically, because the moment of couple is generated across the bracket, the bracket width determines the length of the moment arm (Fig. 1). For example, when a canine bracket is 10mm from the center of resistance and a force of 100g is applied, a l,000g-mm moment is needed to achieve the desired distal canine translation (Fig. 2). If the canine bracket is 4mm wide, about 250g of force will be required at each corner of the bracket; if the bracket is 1,2mm wide, about 830g of force will be needed.
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