pISSN 2234-7518
eISSN 2005-372X

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Fig. 5. Progress and force system for uprighting the mandibular second molar. A, Left mandibular second molar uprighting using a 0.016 × 0.016-inch (in) square nickel-titanium (NiTi) archwire with two step bends whose distance was 2 mm wider than the inter-bracket distance between the left second premolar and the second molar. B, Force system acting on the second molar when the uprighting mechanics using a compression force is employed. Two step bends, whose distance is 2 mm wider than the inter-bracket distance between the second premolar and second molar, are incorporated into a 0.016 × 0.016-in square NiTi archwire. When the two step bends incorporated into the archwire are squeezed and engaged into the brackets, a mesial force to the second premolar and a distal force to the second molar are generated. Then, an uprighting moment (M), whose magnitude is the product of the magnitude of the distal force (F) and the perpendicular distance (d) from its line of force to the center of resistance (CR), is produced. C, The length of the excess wire distal to the buccal tube on the right first molar was used to shift the archwire to the left to reactivate the two step bends without removing the archwire (circle). D, A crimpable stop placed on the archwire just mesial to the anterior step bend (arrow).
Korean J Orthod 2020;50:268~277 https://doi.org/10.4041/kjod.2020.50.4.268
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