Early intervention in the transverse dimension: is it worth the effort?

Participating in the International Symposium on Early Orthodontic Treatment allowed me to review our long-term studies of orthodontic and orthopedic intervention in patients in the mixed and early permanent dentition periods who present with tooth size-arch length discrepancies. I hope this brief synopsis of that research will spur the reader to examine our textbook, a short conceptual article on maxillary transverse deficiency, and the clinical studies summarized below for more detailed explanations of our overall approach to early treatment. Much of the discussion concerning the efficacy and effectiveness of early treatment has centered on the timing of intervention in Class II malocclusion. In our practice, however, aggressive treatment of sagittal Class II problems in the early mixed dentition stage now involves relatively few patients, with intervention restricted to young patients with psychologically or physiologically handicapping malocclusions. Rather, we frequently encounter patients with discrepancies between tooth size and available arch space, typically manifested as crowding. It is well known that there are only 3 ways to manage crowding problems in an adolescent: extraction, interproximal reduction, and expansion (both laterally and posteriorly). In contrast, by intervening during the mixed dentition period, the clinician can take advantage of the leeway space that exists during the transition to the permanent dentition. According to Ann Arbor standards, 4 mm of space is typically available in the maxillary arch and 5 mm in the mandibular arch during the exchange of the second deciduous molars and the second premolars. We routinely place a transpalatal arch before the maxillary second deciduous molars are lost ( 90% of patients), and we use a mandibular lingual arch if conservation of the leeway space is necessary in the mandible. Tooth size-arch length discrepancies can be divided arbitrarily into 3 categories: clear-cut extraction (mandibular crowding 6 mm), clear-cut nonextraction (crowding 3 mm), and borderline crowding problems. Patients with severe crowding in the mixed dentition are often best treated with a serial extraction protocol; large tooth size (eg, maxillary central incisors 10.0 mm wide) is a primary indication for this treatment. Interproximal reduction can be used effectively to resolve mild-to-moderate crowding problems, but we use this procedure primarily during phase II treatment. Orthopedic expansion of the maxilla often is indicated in patients with maxillary constriction (eg, when the maxillary intermolar width is 30 mm). Rapid maxillary expansion (RME) can be used effectively to correct transverse and sagittal crossbite problems and to provide sufficient arch space to resolve borderline crowding in some mixed dentition patients. (As with any treatment protocol, orthopedic expansion must be undertaken with a healthy dose of common sense. Just as all patients should not be treated with extraction, neither should all be treated with RME.) In addition, this procedure can be used to facilitate maxillary canine eruption, flatten the curve of Wilson, improve nasal airflow, and “broaden the smile,” and for other purposes to be mentioned later. Although RME has been used routinely as a treatment modality for crossbite correction for over 3 decades, it only recently has come into regular use for patients without crossbites. In addition, there have been Thomas M. and Doris Graber Endowed Professor of Dentistry, Department of Orthodontics and Pediatric Dentistry, School of Dentistry; Professor of Anatomy and Cell Biology, School of Medicine; Research Scientist, Center for Human Growth and Development, The University of Michigan; and private practice, Ann Arbor, Mich. Presented at the International Symposium on Early Orthodontic Treatment, February 8-10, 2002; Phoenix, Ariz. Am J Orthod Dentofacial Orthop 2002;121:572-4 Copyright © 2002 by the American Association of Orthodontists. 0889-5406/2002/$35.00 0 8/1/124167 doi:10.1067/mod.2002.124167