正畸拔除下颌第二前磨牙和第一磨牙对第三磨牙的影响

Influence on the eruption of mandibular third molar after the extraction of second premolar or first molar during orthodontic treatment

目的:比较青年正畸治疗患者拔除下颌第二前磨牙和下颌第一磨牙对下颌第三磨牙萌出的影响。方法:回顾68例伴随下颌第三磨牙阻生的安氏Ⅰ类青年正畸患者,分别设计不拔牙、拔除下颌第二双尖牙、拔除下颌第一磨牙,采用直丝弓矫治器,闭合曲法关闭拔牙间隙,应用曲面断层片分析三组患者正畸治疗前后下颌第三磨牙倾角和萌出间隙的变化,结果采用t检验统计分析。结果:非拔牙组治疗前后左右下颌第三磨牙倾角(RM3\LM3)、左右下颌第三磨牙萌出间隙(RS\LS)、左右下颌第三磨牙萌出间隙和牙冠宽度比率(Rratio\Lratio)改变无统计学意义(P>0.05);拔除下颌第二前磨牙组RM3、LM3变化无统计学意义(P>0.05);RS、LS、Rratio、Lratio变化有统计学意义(P<0.05);拔除下颌第一磨牙组RM3、LM3变化无统计学意义(P>0.05);其RS、LS、Rratio、Lratio变化有显著的统计学意义(P<0.01)。结论:拔牙矫治有助于下颌第三磨牙萌出间隙的增加,拔除下颌第一磨牙较拔除下颌第二前磨牙产生更显著的下颌第三磨牙后间隙改变,但青年患者拔牙矫治对下颌第三磨牙倾角无明显影响。

Objective To estimate the influence on the eruption of mandibular third molar after extracting the mandibular second premolar or first molar. Methods 68 adolescent cases with Class I malocclusion were studied by retrospective analytic method and divided into three groups：second premolar extraction group,first molar extraction group and non-extraction group.All the cases were finished with straight wire appliance and closed the space by closing loop method.then the third molar＂ angulation,mesio-disto crown width and eruption space were measured on panoramic radiographs pre and after treatment in each group by t-test. Results There was no significant changes of third molar angulation （RM3/LM3）,eruption space （RS/LS） and mesio-disto crown width （Rratio/Lratio） in the non-extraction group （P〉0.05）.There was significant difference of RS,LS,Rratio and Lratio （P〈0.05） in second premolar extraction group,but the change of RM3,LM3 have no statistical meaning （P〉0.05）.ln first molar extraction group,there was significant difference of RS,LS, Rratio and Lratio （P〈0.01）,but the change of RM3,LM3 still have no statistical meaning. Conclusion extraction in Orthodontic can increase the third molar＇ eruption space,the eruption space increased obviously after extracting the first molar.But teeth extraction does not improve the third molar＇ angulation.improve the third molar＇ angulation.