title: A longitudinal study of skeletal side effects induced by rapid maxillary expansion.
abstract: Orthopedic expansion of the maxillary arch--rapid maxillary expansion (RME)--is a commonly used treatment technique that has become increasingly popular during the last 25 years. During this time, however, clinicians routinely have imputed a variety of undesirable side effects to RME, particularly bite opening. Whereas there have been many explanations as to the mechanisms underlying such RME-related effects as bite opening, few studies have considered the long-term effects of RME in the vertical and sagittal dimensions of the face. The purpose of this investigation was to examine cephalometrically the long-term effect that the Haas-type rapid maxillary expansion may have on bite opening and on the anteroposterior position of the maxilla. The sample consisted of 25 patients who had undergone RME with the Haas-type expander, followed by standard edgewise therapy. This RME sample was compared with a group of 25 patients who had standard edgewise treatment (SET) only and with a control (CTRL) group of 23 subjects. Mean initial form and mean age at start of treatment for the RME, SET, and CTRL groups were similar. Statistically significant among-group differences were documented for only 2 of 10 cephalometric variables sensitive to anteroposterior and vertical skeletal changes. These differences, however, were not clinically significant. The current investigation implies therefore that RME therapy with the Haas-type expander has little long-term (more than 6 years after treatment) effect on either the vertical dimensions or the anteroposterior dimensions of the face.
authors.affiliation: Department of Orthodontics and Pediatric Dentistry, University of Michigan, Ann Arbor 48109-1078, USA.
authors.forename: J Y
authors.initials: JY
authors.lastname: Chang
authors.forename: J A
authors.initials: JA
authors.lastname: McNamara
authors.forename: T A
authors.initials: TA
authors.lastname: Herberger
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D002508:Cephalometry / Q000706:statistics & numerical data; D002648:Child; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008310:Malocclusion / Q000000981:diagnostic imaging / Q000628:therapy; D008437:Maxilla / Q000000981:diagnostic imaging / Q000254:growth & development*; D003765:Models, Dental; D009967:Orthodontic Appliances; D010155:Palatal Expansion Technique / Q000009:adverse effects* / Q000706:statistics & numerical data; D011859:Radiography; D012189:Retrospective Studies