Department of Orthodontics, IRCCS Cà Granda–Ospedale Maggiore Policlinico, University of Milan, Italy.
Angle Orthod. 2011 Mar;81(2):298-303. doi: 10.2319/050410-241.1.
To evaluate and compare the skeletal vertical and sagittal effects of the Hyrax expander in Class I, II, and III patients.
One hundred and eighty-three patients (91 females, 92 males) with a mean age of 8.7 years and with maxillary bilateral cross-bite and maxillary hypoplasia were analyzed retrospectively. They were divided into three groups according to their skeletal class. Sixty-five patients were skeletal Class I, 55 were skeletal Class II, and 63 were skeletal Class III. For each patient a lateral cephalogram was obtained before treatment and at the end of the retention period. Changes in the groups during the observation period were calculated, compared, and statistically analyzed with a t-test.
In terms of vertical effects, a statistically significant increase in the anterior vertical dimension was observed only in Class III patients. No statistically significant changes were observed in the posterior vertical dimension in any of the groups. In terms of sagittal effects, in Class I patients the maxilla and the mandible moved forward, but not in a statistically significant way, and the ANB angle showed a statistically significant decrease, but its change was less modified. In Class II patients the maxilla moved forward, but not in a statistically significant way, while the mandible moved forward in all of the patients in a statistically significant manner. The ANB decreased, statistically improving the skeletal classification. In Class III patients the maxilla moved forward in a statistically significant manner; the mandible showed a downward and backward rotation, improving the skeletal classification.
The data obtained in this study permit us to confirm that rapid maxillary expansion can be used in all of the skeletal classes with good vertical and sagittal results.
评估并比较 Hyrax 扩弓器在 I 类、II 类和 III 类患者中的骨骼垂直和矢状向效应。
回顾性分析了 183 名（91 名女性，92 名男性）平均年龄为 8.7 岁、存在上颌双侧交叉咬合和上颌发育不全的患者。根据骨骼类型将他们分为三组。65 名患者为骨骼 I 类，55 名患者为骨骼 II 类，63 名患者为骨骼 III 类。每位患者在治疗前和保持期结束时均获得侧位头颅侧位片。计算并比较各组在观察期间的变化，并使用 t 检验进行统计学分析。
在垂直向效应方面，仅在 III 类患者中观察到前垂直向尺寸有统计学意义的增加。在任何一组中，后垂直向尺寸均无统计学意义的变化。在矢状向效应方面，I 类患者的上颌和下颌向前移动，但无统计学意义，ANB 角显示统计学上的显著减小，但变化程度较小。II 类患者的上颌向前移动，但无统计学意义，而所有患者的下颌均以统计学意义的方式向前移动。ANB 减小，骨骼分类得到统计学改善。III 类患者的上颌以统计学意义的方式向前移动；下颌呈向下和向后旋转，改善了骨骼分类。
本研究获得的数据使我们能够确认快速上颌扩展可用于所有骨骼类型，均能获得良好的垂直和矢状向效果。
