In children, maxillary widening often does not require surgical intervention since the mid-palatal suture is still patent; the maxilla is widened simply by placing a RME appliance in the palate anchored to the teeth. Biologically, fusion of the mid-palatal suture occurs during the early teens and often coincides with the pubertal growth spurt [7]. Any attempts to expand the maxilla after the sutures have fused often incorporate surgical osteotomy to facilitate expansion. Even so, the expanders still exert lateralizing forces on the dentition, and expansion forces tend to concentrate more on the supporting dental segments rather than the mid-palate or nasal oor. In 1964, a study by Krebs on orthopedic transverse modication demonstrated that expansion is 50% skeletal and 50% dental in younger children while the percentage dramatically changes to 35% skeletal and 65% dental in adolescents [8]. Over the years, there have been many RME design modications to minimize den­tal side effects while maximizing skeletal expansion.