In all wire sizes, once the lower arch form has been established, the upper archwire needs to be coordinated to the lower archwire. In general, this is achieved by adjusting the upper archwire so that it is 3 mm wider anteriorly and posteriorly than the lower archwire. This helps to establish the correct 3 mm of overjet both anteriorly and posteriorly. Because of posterior torque considerations (see below), it may be beneficial in many cases to widen the upper arch in the posterior segments to approximately 5 mm. If these procedures are followed during treatment, there is normally little need to adjust archwire coordination during the finishing stages of treatment.
Some cases may show slight narrowing in the posterior segments near the end of treatment, and a .045 archwire can be coordinated with the upper arch form and widened approximately 6 mm per side. It can then be secured to the upper arch in the headgear tubes (p. 82). This supplemental or 'jockey wire' is beneficial in taking care of minor maxillary narrowing in the finishing stages of treatment.
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