Fig. 6 Fig. 7 Fig. 8 Brackets From a Coupling Force Aspect ᕡ Equal and opposite forces cancel each other out. So, if we have a 2-ounce force pushing in equal and opposite directions, the net force is 0. (Fig. 9) ᕢ Now, move the forces out about 1 mm each. There is a rotation force of about 4 ounces. (Fig. 10) ᕣ Move that same 2-ounce force out to 2 mm. Now we have a rotational force of about 8 ounces. Fig. 9 (Fig. 11) Bottom line: The longer the bracket, the more coupling force can be produced, but this also increases the friction of the bracket so it’s harder to move the tooth down the wire. Brackets Systems From Prospective of Coupling Forces ᕡ Straight Wire Bracket design (Fig. 12) : • Long mesial-buccally for control and to create www.orthodontics.com Spring 2017 31
Journal of the American Orthodontic Society Spring 2017: Page 31
