Qualitative Description of the Effects of Rapid Maxillary Expansion: a Three-Dimensional Perspective

Background: The effects of rapid maxillary expansion (RME) have been widely studied with classic bidimensional imaging. Objectives: The study aimed to determine immediate post-expansion effect of RME with three-dimensional imaging.Methods: Computed tomography (CT) low dose scan records were taken for three patients before applying RME (T0), and imme- diately after the end of the active expansion phase (T1). For one patient a CT scan was available also at T2, at time of RME removal. Image analysis was done in 4 steps: segmentation of the face skull, model construction and exportation of .stl surface shells, cranial base superimpositions and colorimetric maps overlay.Results: There were differences in the bone adaptations to RME, but it was possible to identify some common trends in the three patients. All of the three patients showed a pattern of forward movement of the maxilla associated to the suture opening. Patients 1 and 3 demonstrated also a downward movement of the maxilla, which was not visible on patient 2. As a sagittal advancement of almost 6 mm, as visible in patients 1 and 3, was not possible due to growth in only two weeks, all bony changes could be attributed to the RME. For patient 1, the bony changes present at T1, were still present at T2, while the suture was closed.Conclusions: A pattern of forward immediate displacement of the maxilla with respect to the cranial base was consistently noticed in three patients. The vomer bone maintained a connection with one half of the maxilla when the suture opened.