Treatment with the mandibular Arnold expander.

Dr. Kravitz is a Contributing Editor of the Journal of Clinical Orthodontics; an adjunct faculty member, Department of Ortho dontics, Washington Hospital Center, Washington, DC; and in the private practice of orthodontics at 25055 Riding Plaza, Suite 110, South Riding, VA 20152; e-mail: nealkravitz@ gmail.com. D crowding—otherwise referred to as tooth-size/arch-length discrepancy (TSALD) —is the most common component of malocclusion among orthodontic patients. According to the National Center for Health Statistics, 40% of preadolescent children and 85% of adolescents exhibit TSALD.1,2 Particularly prevalent in the mandibular arch, it is often the determining factor in the decision whether to extract teeth. Relief of crowding is more challenging in the lower arch than in the upper arch because of the absence of a midline suture and the resistance of the mandibular body. Any attempt to achieve substantial mandibular dental expansion with fixed appliances can result in undesirable incisor and canine proclination outside the supported bony housing, which can strain the periodontium, alter the occlusion, and increase the potential for relapse. Therefore, the pretreatment mandibular intercanine width has been considered an inviolable measurement.3-6 Moderate increases in mandibular intercanine width may be possible, however, if expansion is begun prior to the eruption of the permanent canines.7,8 This article describes the use of the Arnold expander*—also known as the expansion arch or E-arch—as a means of mandibular expansion in patients with moderate TSALD. Although the mandibular Arnold expander is most commonly applied during early interceptive treatment, its use during late adolescence will also be discussed.