345例青少年恒磨牙发育情况的回顾性研究

Retrospective study of 345 cases of young permanent molar development

目的分析常州市11～14岁青少年恒磨牙（主要是第二磨牙M2和第三磨牙M3）的影像学表现,横向研究恒磨牙的发育、萌出情况,以及M3、M2的发育关系。方法从常州市口腔医院影像资料中抽取2013年1～10月期间拍摄的11～14岁青少年的全颌曲面断层片共345张,分别观察M3、M2的发育情况并进行发育分期,分析两者的相关性。结果在11～14岁青少年中,M2处于发育G期的比例为43.26%,下颌整体发育早于上颌（Z=-11.69,P〈0.001）,女性较男性发育早（Z=-3.06,P=0.002）;21颗阻生,均为下颌近中倾斜,占下颌M2总数的3.04%。M3处于发育C期的比例为33.26%,女性比男性发育早（Z=-2.06,P=0.040）,下颌M3发育早于上颌（Z=-3.42,P=0.001）。经Spearman相关分析,M3与M2存在相关性（r=0.869,P〈0.001）。结论青少年中M2与M3的发育密切相关,除去生长因素外、上下颌牙弓后段能否同时容纳、是否容易导致复发等,在正畸治疗时需要充分考虑两者的关系。

Objective To analyze the imaging manifestations of second molar（ M2） and third molar（ M3） in children aged 11-14 in Changzhou City,and to explore the relationship of development between M3 and M2. Methods A total of 345 adolescents with 11-14 years old,of Changzhou Stomatological Hospital in January-October,2013 were selected as the imaging database. The M3 and M2 on the panoramic radiographs were observed for the development degree in 345 cases. And then the correlation analysis was done. Results In the all adolescents,43. 26% of M2 was in stage G. The development of M2 appeared earlier in the mandibular than in the maxillary（ Z =- 11. 69,P〈0. 001） and earlier in female than in male（ Z =- 3. 06,P = 0. 002）; 21 teeth were impacted and tilted in the mandibular,it was 3. 04% of the mandibular M2. 33. 26% of M3 was in stage C. The development of M3 appeared earlier in female than male（ Z =- 2. 06,P = 0. 040）,and earlier in the mandibular than in the maxillary（ Z =- 3. 42,P = 0. 001）. M3 and M2 had positive correlation when calculated by Spearman correlation coefficient（ r = 0. 869,P〈0. 001）. The difference was statistically significant. Conclusions M2 and M3 in adolescents was closely related to the development. It was necessary to consider fully the relationship between the two in orthodontic treatment.