Rapid maxillary expansion: Effects on palatal area investigated by computed tomography in growing subjects

The aim of this prospective study was to evaluate the effects of rapid maxillary expansion (RME) on the palatal area as assessed by low-dose CT before treatment (T0), at the end of active expansion (T1) and after a retention period of 6 months (T2).The study sample comprised 17 prepubertal subjects (mean age 11.2 years) with constricted maxillary arches. Total amount of expansion was 7 mm in all subjects. Multi-slice low-dose CT scans were taken at T0, T1, and T2. On axial CT scanned images a circle line corresponding to the palatal area was drawn and the area inside the circle registered at all three observation times. The area was measured in mm². Statistical comparisons were carried out with Friedman test with post-hoc tests (P0.05).The palatal area showed a significant increase from T0 to T1 and from T0 to T2 as a consequence of the opening of the midpalatal suture after RME.Opening the midpalatal suture by using orthopedic forces allowed to extend the area of the maxilla. After a 6-months retention period the palatal area demonstrated a stable increase due to a bone deposition along the midpalatal suture in both the anterior and posterior parts of the maxilla.