A longitudinal study of skeletal rapid maxillary expansion side effects induced by

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 tong-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 Haastype expander has little long-term (more than 6 years after treatment) effect on either the vertical dimensions or the anteroposterior dimensions of the face. (Am J Orthod Dentofac Orthop 1997;112: 330-7.)