Treatment and posttreatment skeletal effects of rapid maxillary expansion studied with low-dose computed tomography in growing subjects.

INTRODUCTION The aim of this study was to apply low-dose computed tomography (CT) to evaluate treatment and posttreatment effects produced by rapid maxillary expansion (RME) at the levels of the midpalatal suture and the pterygoid processes. METHODS A sample of 17 subjects (7 boys, 10 girls; mean age, 11.2 years) was analyzed. Multi-slice CT scans were taken before RME, at the end of the active expansion phase, and after a retention period of 6 months. Statistical analysis was performed with ANOVA for repeated measures with post-hoc tests. RESULTS The amounts of opening of the midpalatal suture during the active phase of expansion were 3.01, 2.17, and 1.15 mm for the anterior, middle, and posterior suture widths, respectively. Pterygoid width also showed a statistically significant increase (1.49 mm). In the postretention period, all transverse measurements had significant decreases except for pterygoid width. CONCLUSIONS At the end of the retention phase after RME therapy, the transverse width of the midpalatal suture was similar to the pretreatment width, whereas the width between the pterygoid processes was significantly increased.