Micro-implant-assisted expanders have shown significant effects on the mid-face, including a degree of asymmetry. The aim of this study is to quantify the magnitude, parallelism, and asymmetry of this type of expansion in non-growing patients. A retrospective study on a sample of 31 non-growing patients with an average age of 20.4 years old, with cone beam computed tomography images taken before and right after expansion using maxillary skeletal expander (MSE) were assessed for skeletal expansion at three landmarks bilaterally. Average magnitude of total expansion was 4.98 mm at the anterior nasal spine (ANS) and 4.77 mm at the posterior nasal spine (PNS) which showed statistical significance using a paired t test with p < 0.01. Average expansion at the PNS was 95% of that at the ANS. The sample was divided into symmetric (n = 15) and asymmetric (n = 16) based on the difference in expansion at the ANS, with 16 out of 31 patients exhibiting statistically significant asymmetry. MSE achieves distinctly parallel expansion in the sagittal plane but can exhibit asymmetrical expansion in the transverse plane.

中文翻译：

---

对非成长型患者中微植入物辅助的快速上颌骨扩张的幅度，平行度和不对称性的评估

微植入物辅助的扩张器已对中脸显示出显着效果，包括一定程度的不对称性。这项研究的目的是量化在非成长型患者中这种类型的扩张的幅度，平行性和不对称性。回顾性研究了31名平均年龄为20.4岁的未增长患者的样本，并使用上颌骨扩张器（MSE）在扩张前后进行了锥形束计算机断层扫描图像，评估了双侧三个标志物的骨骼扩张情况。鼻前壁（ANS）的平均总扩张量为4.98 mm，鼻后壁（PNS）的平均总扩张量为4.77 mm，使用配对t检验（p <0.01）显示出统计学意义。PNS的平均扩张是ANS的95％。根据ANS扩张的差异，将样本分为对称（n = 15）和不对称（n = 16），在31名患者中有16名表现出统计学上的显着不对称性。MSE在矢状平面上实现了明显的平行扩展，但在横向平面上却表现出不对称的扩展。