减数下颌第一前磨牙对下颌第三磨牙萌出状态影响的锥形束CT研究

The effect of orthodontic treatment with first premolar extraction on eruption of mandibular third molar:a cone beam CT study

目的探讨减数下颌第一前磨牙正畸治疗前后下颌第三磨牙萌出状态的变化,并分析影响其倾斜角度变化的因素。方法本研究为回顾性研究,样本最终纳入正畸患者40例,共含68颗下颌第三磨牙,利用三维测量软件测量分析下颌第三磨牙位置及角度。配对t检验及秩和检验比较下颌第三磨牙的位置变化,多元回归分析可能影响其近中倾斜角度变化的因素。结果正畸治疗后下颌第三磨牙近中移动(1.59±3.35)mm(P=0.012),向近中倾斜10.24°±18.82(P<0.001)。患者治疗前ANB角,下颌平面角,萌出高度(8Cp-X),初始角度(∠78)以及下颌第二磨牙远中间隙的变化(△D7-Xi)对第三磨牙近中倾斜角度变化(△∠78)的影响无统计学意义(F=2.153,P=0.071)。结论正畸减数下颌第一前磨牙后,下颌第三磨牙有近中移动和近中倾斜角度加大的趋势,临床医师在治疗设计时应综合考量。

Objective To evaluate the changes of mandibular third molars influenced by orthodontic treatment with first premolar extraction and analyze influencing factors of its angulation changes.Methods This is a retrospective cohort study and a total of 40 patients with 68 mandibular third molar were included.Three-dimensional software was used for evaluating position and angulation of mandibular third molar.Paired t-tests and Wilcoxon tests were performed to compare treatment changes and multiple regression analysis were later processed to find influencing factors about angulation changes.Results The third molars moved forward(1.59±3.35)mm(P=0.012)with 10.24°±18.82°(P<0.001)angulation changes after orthodontic treatment.The ANB angle,the mandibular plane angle,the distance from the central pit of third molar to horizontal plane and the angle between second and third molar long axis before treatment and changes of retromolar space didn't make a significant difference in angulation changes of third molar(F=2.153,P=0.071).ConclusionsMandibular third molar moved forward and the angulation changes of mandibular third molar increased after first premolar extraction.Orthodontists should be aware of that during making treatment plans.