In patients with constricted maxilla, normal transverse dimension of the maxilla is best achieved by orthopedic expansion which involves the use of a heavy force applied across the midpalatal suture, to move both halves away from each other. This may be accomplished with hyrax - type expansion screw, by turning it twice a day, producing 0.5mm of opening per day, delivering a force of 5 to 7 pounds, with an active treatment period of 2 - 3 weeks. As many maxillary teeth as possible should be ideally included in the anchorage unit. The concept of rapid maxillary expansion is based upon the fact that the forces are applied to the anchorage teeth at a rate and magnitude beyond their capacity to respond.
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