Abstract:

Abstract： Objective To evaluate the effect of rapid and slow palatal expansion with Hyrax for correcting narrow maxilla during late mixed dentition. Methods Sixty adolescent patients at late mixed dentition with transverse deficiencies were divided into two groups. They received RME treatment and SME treatment. They received cone beam computerized tomography scans before and after expansion. With three-dimensional reconstruction on Invivo5 software， items were measured including maxillary width at the level of hard palate， buccal dental arch width ， angle of bilateral inclination alveolar ， angle of bilateral inclination teeth，and buccal and lingual bone thickness in maxillary first molar and first premolar. The data was statistically analyzed. Results Oronal - There was no difference in two groups in bone effect and buccal dental arch width. Buccal dental arch width increased after expansion， bone effect in first premolar was more significant than first molar. The alveolar bone reconstruction and teeth tipping were obvious. The alveolar bone reconstructions in slow maxillary expansion group were more obvious than rapid maxillary expansion group， but teeth tipping in rapid maxillary expansion group was more obvious than slow maxillary expansion group. Axial - buccal bone thickness was reduced， lingual bone thickness was increased， but buccal reduction in rapid maxillary expansion group was more than slow maxillary expansion group. Two groups were significantly different. Conclusion Compared with rapid maxillary expansion， slow maxillary expansion meets the physical characteristics with slight force，which is an effective form of arch expansion with little influence on buccal bone thickness at late mixed dentition patients.

Key words: Hyrax, slow maxillary expansion, rapid maxillary expansion, narrow maxilla

摘要：

目的 比较Hyrax快速与慢速扩弓矫治替牙晚期上颌狭窄的疗效。 方法 选取2011年1月至2012年12月来大连市口腔医院正畸科就诊的替牙晚期上颌基骨狭窄患者60例，随机分成2组，分别采用Hyrax快速扩弓与Hyrax慢速扩弓进行矫治，扩弓前后拍摄锥形束CT（cone beam computerized tomography ，CBCT），通过Invivo5牙科软件三维重建，分别测量扩弓前后上颌第一磨牙、第一前磨牙冠状位硬腭水平基骨宽度、颊侧牙弓宽度、双侧牙槽骨倾斜角度的交角、双侧牙齿倾斜角度的交角，轴位颊、舌侧骨质厚度。扩弓前后数据采用SPSS 17.0统计软件进行分析。结果 冠状位：Hyrax快速扩弓与Hyrax慢速扩弓在骨性开展和牙弓总宽度变化上无差别，扩弓后牙弓总宽度增加，第一前磨牙平面的骨开展量大于第一磨牙平面，牙齿和牙槽嵴颊向倾斜，牙槽嵴倾斜的角度慢速扩弓组大于快速扩弓组，牙齿倾斜的角度快速扩弓组大于慢速扩弓组；轴位：颊侧骨质厚度减少，舌侧骨质厚度增加，但Hyrax慢速扩弓组颊侧的减少量小于Hyrax快速扩弓组，两组差异有统计学意义（P＜0.05）。结论 对于替牙晚期患者，与Hyrax快速扩弓相比，Hyrax慢速扩弓慢速轻力的特点更符合生理特性，并且对颊侧的骨质厚度影响小，是一种有效的扩弓方式。

关键词: Hyrax扩弓器, 慢速扩弓, 快速扩弓, 上颌狭窄