Three-dimensional densitometric analysis of maxillary sutural changes induced by rapid maxillary expansion

AIM:To prospectively evaluate the density of the midpalatal and transverse sutures 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. 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 the axial CT scanned images six regions of interest (ROIs) were placed along the midpalatal and transverse sutures (MpS Ant, MpS Mid, MpS Post, MpS/TS, TS left, TS right) and two in the maxillary and palatal bony areas. Density was measured in Hounsfield Units. Mann-Whitney U test and Friedman ANOVA with Tukey’s post-hoc tests were used (P < 0.05). RESULTS: The three ROIs in the midpalatal suture showed a significant decrease in density from T0 to T1, a significant increase from T1 to T2, and lack of statistically significant differences from T0 to T2. Both ROIs located in the transverse suture showed a significant decrease in density from T0 to T1 that was followed by a non-significant increase in density from T1 to T2. CONCLUSION: At the end of T1 a significant reduction in density along the midpalatal and transverse sutures was observed in all subjects. The sutural density of the midpalatal suture at T2 indicated reorganization of the midpalatal suture while the density along the transverse suture increased without reaching the pre-treatment values, probably due to different morphology between the midpalatal and transverse sutures. The findings support the hypothesis that orthopaedic stimulation of the midpalatal suture significantly influences the transverse suture, with clinical implications regarding the benefit of palatal expansion in subjects requiring maxillary protraction.