Abstract: Objectives: To compare the differences of teeth movement after rapid maxillary expansion or slow maxillary expansion in teenagers. Methods: Forty patients in the growth peak with narrow arch were selected. They were randomly divided into two groups. CBCT imaging technique was used to scan and reconstruct the arch before and after maxillary expansion. The changes of teeth and palate were measured and analyzed statistically. Results: For rapid expansion group, the increase of gap between the crowns was smaller and the increase of gap between the roots was bigger than those of slow expansion group (P<0.05). Conclusion: During maxillary expansion, the teeth have both whole movement and tilt movement. The whole movement in the rapid expansion group was greater than that of the slow expansion group.

Key words: Maxillary expansion, Tooth movement, Ratio of bone and tooth, CBCT