关键词: Hyrax扩弓器, 慢速扩弓, 快速扩弓, 上颌狭窄

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