| Objective: To test the null hypothesis that the spheno-occipital synchondrosis does not show bony displacement in response to rapid maxillary expansion (RME) therapy in youngsters. Materials and Methods: A total of 16 computed tomography (CT) records were taken from 8 growing patients (2 males and 6 females), before (T0) and after (T1) treatment with RME. All patients had been diagnosed originally with transverse maxillary deficiency. The mean chronological age of the patients was 9.8 ± 1.8 years (range, 8 to 11.4 years). High-resolution multislice multidetector CT was used to study quantitatively the extent of the opening of the spheno-occipital synchondrosis following RME. A low-dose CT scan protocol was used (80 kV, 10 mA) and the data file of each patient was transferred to a workstation where the anteroposterior width of the spheno-occipital synchondrosis was measured on axial images. Results: Before treatment with RME (T0), the anteroposterior mean width of the spheno-occipital synchondrosis was 1.73 ± 0.46 mm immediately after the active phase of expansion (T1), and the width of the synchondrosis increased to 2.30 ± 0.47. This difference was statistically significant according to the Wilcoxon signed rank test (P < .05). Conclusion: Rapid maxillary expansion leads to a small immediate widening of the spheno-occipital synchondrosis in youngsters.
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