Prediction of arch perimeter changes due to orthodontic treatment.

A borderline orthodontic case with mild to moderate space deficiency can be treated without extractions. Expansion can be used to relieve space deficiency. The prediction of arch perimeter change for a given amount of expansion is helpful in planning the treatment of a patient who needs expansion, and it can facilitate nonextraction orthodontic treatment.

Extrusion-based leveling with segmented arch mechanics.

Leveling of the dental arch may be accomplished through anterior intrusion, posterior extrusion, or a combination. Posterior extrusion is usually preferred in vertically balanced adolescents and in surgical-orthodontic treatment of adults suffering from deep bite and mandibular deficiency. A major disadvantage of posterior extrusion, when accomplished by continuous archwires, is incisor flaring.