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

Abstract

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. (Am J Orthod Dentofacial Orthop 2008;134:389-92)

Modifications of midpalatal sutural density induced by rapid maxillary expansion: A low-dose computed-tomography evaluation

“…This difference in density explains the greater opening in the anterior vs the posterior sutural regions after the active phase of expansion, as demonstrated in a previous study. 9 Lione et al 9 reported that the amount of transverse increase at the middle sutural width (corresponding to PS ROI in our study) was about 70% of that observed in the anterior sutural width (corresponding to AS ROI in our study).…”

“…6 Recently, the opening of the midpalatal suture after RME was evaluated with computed tomography (CT), which provides accurate 3-dimensional assessment of skeletal changes. [7][8][9] The use of CT has been proposed also for the quantitative evaluation of bone density with the Hounsfield index in selected regions of interest (ROI). 10 The same index has been used to assess bone density for implant placement in the maxillary bones.…”

CBCT of skeletal changes following rapid maxillary expansion to increase arch-length with a development-dependent bonded or banded appliance

“…5,19 For the standardized 5-mm activation, the mean expansion between the Mx6s was approximately 4.3 mm (86%) for the bonded (McNamara-type) RME patients compared to 4.0 mm (80%) in the banded (Hyrax-type) groups (Table 1). This relatively efficient RME may reflect the concurrent expansion of the lower arch.…”

“…There are many 2D reports indicating a nonparallel, triangular expansion pattern: greater expansion in the anterior rather than the posterior dimension. 19,20,33 However, there have been only a few studies that have focused on the effects of RME on craniofacial sutures by evaluating the frontal (coronal) dimension. [34][35][36][37] Overall, the present literature review suggests the bonded appliance is the optimal appliance before the maxillary first premolars (Mx4s) erupt, and the banded expander is more desirable thereafter.…”

“…[13][14][15] Traditionally, the effects of RME are evaluated using casts and/or two-dimensional (2D) radiographs, but reproducibility of 2D radiographs is problematic, and overlapping images are difficult to assess. [16][17][18] Conebeam computed tomography (CBCT) provides more accurate and reproducible imaging 19,20 for assessing all craniofacial skeletal structures, including the circummaxillary sutures. [21][22][23] Common RME appliances are the bonded (McNamara type) [24][25][26][27] and the tooth banded (Hyrax type).…”