Skeletal changes induced by rapid maxillary expansion assessed with sutural density analysis on low-dose computed tomography

AIM: The measurement of sutural density represents a contemporary approach to determine the outcome of orthopaedic intervention on the transverse dimensions of the maxilla and ideal timing for retention of maxillary expansion. The aim of this research was to evaluate the density of the midpalatal suture as assessed by low-dose computed tomography (CT) before rapid maxillary expansion (RME, T0), at the end of active expansion (T1) and after a retention period of 6 months (T2). SUBJECTS AND METHOD: Seventeen prepubertal subjects (mean age 11.2 years) with constricted maxillary arches, and uni or bilateral posterior crossbites. The 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 four regions of interest (ROIs) were placed along the midpalatal suture (anterior, AS ROI, and posterior, PS ROI) and in two regions of palatal bone (anterior and posterior). Density was measured in Hounsfield units. Mann-Whitney U test and Friedman ANOVA with post-hoc test were used (P < 0.05). RESULTS: The densities in the AS and PS ROIs were significantly smaller than reference bone densities before RME. Both AS and PS ROIs showed a significant decrease in density from T0 to T1, a significant increase from T1 to T2, and a lack of a significant difference from T0 to T2. CONCLUSION: Effective opening of the midpalatal suture by RME in prepubertal subjects was associated with a significant decrease in sutural density. Sutural density at T2 indicated reorganization of the midpalatal suture.