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

AIM: 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). MATERIALS AND METHODS: 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 (P<0.05). RESULTS: 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. CONCLUSION: 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.