Date of Award



Department of Orthodontics

First Advisor

Jonas Bianchi


Background: Maxillary expansion has long been used in children and adolescents for transverse discrepancies and dental crowding. With age, the mid-palatal suture becomes increasingly mature, requiring heavy, rapid force in order to achieve skeletal expansion. As an individual grows into adulthood, it has been demonstrated that a skeletally anchored expander can be used in order to achieve successful sutural separation. The side effects between these two types of expanders, including dental tipping with relative extrusion of buccal segments and clockwise mandibular rotation, have been demonstrated to have differences in their degrees of severity. However, most of the studies have evaluated the effects immediately following the expansion and not through a prolonged period in which growth may occur. The purpose of the present study was to investigate long-term skeletal differences in two types of expansion (RPE vs MARPE) on a growing population. Methods: This retrospective study included 39 adolescent subjects (mean age = 13.8 years) who had received maxillary expansion (20 RPE, 19 MARPE) with subsequent completion of orthodontic treatment. Initial and final CBCTs were used to analyze cephalometric and transversal changes between the two groups. Transverse measurements were repeated two weeks apart to test intra-observer reliability. Results: Cephalometric analysis demonstrated no significant differences in changes of FMA (p = 0.549) or MP-SN (p = 0.722) between the two groups following expansion and completion of orthodontic treatment. There were statistically significant differences in transverse changes between the two groups, with the MARPE group displaying more skeletal expansion. Conclusions: The results of the present study suggest that skeletally anchored expander - MARPE and conventional expander have similar skeletal effects in adolescents.