Department of Orthodontics, Pontifical Catholic University of Rio Grande Do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
Am J Orthod Dentofacial Orthop. 2011 Sep;140(3):366-76. doi: 10.1016/j.ajodo.2010.07.025.
The purposes of this study were to evaluate and compare the immediate effects of rapid maxillary expansion (RME) in the transverse plane with Haas-type and hyrax-type expanders by using cone-beam computed tomography.
A sample of 33 subjects (mean age, 10.7 years; range, 7.2-14.5 years) with transverse maxillary deficiency were randomly divided into 2 groups: Haas (n = 18) and hyrax (n = 15). All patients had RME with an initial activation of 4 quarter turns followed by 2 quarter turns per day until the expansion reached 8 mm. Cone-beam computed tomography scans were taken before expansion and at the end of the RME phase. Maxillary transversal measurements were compared by using the mixed analysis of variance (ANOVA) model and the Tukey-Kramer method.
RME increased all maxillary transverse dimensions (P <0.0001). There was less expansion at skeletal than dental levels. The hyrax group had greater statistically significant orthopedic effects and less tipping tendency of the maxillary first molars compared with the Haas group.
Both appliances were efficient in correcting a transverse maxillary deficiency. The pure skeletal expansion was greater than actual dental expansion. The hyrax-type expander produced greater orthopedic effects than did the Haas-type expander, but this effect was less than 0.5 mm per side and might not be clinically significant.
本研究旨在通过锥形束计算机断层扫描评估和比较快速上颌扩张（RME）在横向上哈斯式和Hyrax 式扩弓器的即刻效果。
将 33 名（平均年龄 10.7 岁，范围 7.2-14.5 岁）上颌横向发育不足的患者随机分为 2 组：哈斯式（n=18）和 Hyrax 式（n=15）。所有患者均接受 RME，初始激活 4 个四分之一转，每天增加 2 个四分之一转，直至扩张达到 8mm。在扩张前和 RME 阶段结束时进行锥形束计算机断层扫描。使用混合方差分析（ANOVA）模型和 Tukey-Kramer 方法比较上颌横向测量值。
RME 增加了所有上颌横向尺寸（P<0.0001）。骨骼水平的扩张小于牙水平。与哈斯组相比，Hyrax 组具有更大的矫形效果和上颌第一磨牙较小的倾斜趋势。
两种矫治器都能有效纠正上颌横向不足。纯骨骼扩张大于实际牙齿扩张。Hyrax 式扩弓器产生的矫形效果大于哈斯式扩弓器，但每侧小于 0.5mm，可能无临床意义。
