Abstract: Objective    To analyze the correlation between the inclination angle of ectopic eruption of first permanent molars and root resorption of second deciduous molars in panoramic radiographs. Methods    Totally 690 first permanent molars suffering ectopic eruption treated in the Department of Pediatric Dentistry of Zhongshan People′s Hospital from 2015 to 2020 were included. Root resorption of the second deciduous molars was classified into grade Ⅰ ~ Ⅳ，and the inclination angle of the first permanent molars suffering ectopic eruption was correspondingly measured. Finally，the correlation between them was analyzed. Results    The inclination angles of maxillary first permanent molars were（102.2 ± 8.5）°，（98.8 ± 8.8）° and（92.7 ± 8.5）°，respectively，which were next to the second deciduous molars with root resorption of grades Ⅱ，Ⅲ and Ⅳ. There was significant negative relationship between them （r = -0.4，P < 0.05）. The inclination angles of mandibular first permanent molars were（58.5 ± 6.4）°，（61.4 ± 8.4）°，（61.9 ± 9.4）°，（61.7 ± 9.0）°，respectively，which were next to the second deciduous molars with root resorption of gradesⅠ，Ⅱ，Ⅲ and Ⅳ. No statistical difference was found in the correlation between them（r = 0.1，P > 0.05）. Conclusion    In cases of ectopic eruption of maxillary first permanent molar，the smaller the mesial inclination angle，the more likely to lead to and aggravate the abnormal root resorption of second deciduous molars.

Key words: first permanent molar, ectopic eruption, inclination angle, second deciduous molar, root resorption, panoramic radiographs

摘要： 目的    通过曲面体层片测量分析第一恒磨牙异位萌出倾斜角度与第二乳磨牙牙根吸收程度的相关性。方法    选取2015—2020年于中山市人民医院儿童口腔科就诊的第一恒磨牙异位萌出患儿473例，共计患牙690颗，将其相邻第二乳磨牙牙根吸收程度分为Ⅰ ~ Ⅳ级。测量第一恒磨牙近中倾斜角度，并分析其与第二乳磨牙牙根吸收程度的相关性。结果    上颌第二乳磨牙牙根吸收Ⅱ ~ Ⅳ级的相邻第一恒磨牙倾斜角度依次为（102.2 ± 8.5）、（98.8 ± 8.8）、（92.7 ± 8.5）°，两者之间存在显著的负相关性（r = -0.4，P < 0.05）。下颌第二乳磨牙牙根吸收Ⅰ ~ Ⅳ级的相邻第一恒磨牙倾斜角度依次为（58.5 ± 6.4）、（61.4 ± 8.4）、（61.9 ± 9.4）、（61.7 ± 9.0）°，两者之间无显著相关性（r = 0.1，P > 0.05）。结论    上颌第一恒磨牙异位萌出时，其近中倾斜角度越小，越可能导致并加重第二乳磨牙牙根的异常吸收。

关键词: 第一恒磨牙, 异位萌出, 倾斜角度, 第二乳磨牙, 牙根吸收, 曲面体层片