Nolla分期对青少年拔牙正畸患者下颌第三磨牙倾斜角的影响

The effects of Nolla stage on mandibular third molar angulation in teenager orthodontic extraction treatment

目的:研究不同Nolla分期对青少年拔牙正畸患者下颌第三磨牙倾斜角的影响。方法:纳入拔除4颗前磨牙的青少年患者120例下颌第三磨牙共120颗,按照Nolla分期分为牙冠正在形成组(A)、牙冠基本形成组(B)、牙根形成<1/2组(C)及牙根形成>1/2组(D)(n=30),测量正畸治疗前后下颌第三磨牙倾斜角α的变化。结果:C组的下颌第三磨牙α角(°)治疗前后分别为65.18±12.72和47.38±20.44(P<0.05),A、B、D组治疗前后α角度变化无统计学意义(P>0.05),C组与其他组之间差异有统计学意义(P<0.05)。结论:青少年患者在牙根形成<1/2时进行拔牙正畸治疗,易导致下颌第三磨牙近中倾斜加重,不利于下颌第三磨牙的竖直。

Objective:To study the effects of orthodontic extraction treatment in different Nolla stages on mandibular third molar angulation.Methods:According to Nolla stage,120 mandibular third molars of 120 teenagers aged 12-18 years and with the extraction of 4 premolars in orthodontic treatment were included and divided into crown forming group(A),crown completion group(B),less than half root completion group(C)and more than half root completion group(D)(n=30).The angulation(α)of mandibular third molars before and after orthodontic treatment were measured and analyzed.Results:In group C theα(°)before and after treatment was 65.18±12.72 and 47.38±20.44 respectively(P<0.05),that in other groups were not significant changed(P>0.05).The change of group C after treatment was greater than that of other groups(P<0.05).Conclusion:If orthodontic extraction treatment is applied when mandibular third molar is at the Nolla stage of less than half root completion,it may lead to more change of mesial inclination and impaction of mandibular third molar.