拔除第一磨牙矫治后第三磨牙萌出情况初探

The initial observation on the third molar eruption after the first molar extraction followed by orthodontic treatment

目的:通过比较不同拔牙方法矫治后第三磨牙萌出的情况,评价拔除第一磨牙矫治对第三磨牙萌出的影响。方法:选取拔除第一磨牙矫治、拔除第一前磨牙矫治和非拔牙矫治3组病例(上颌各20例、下颌各30例),对全颌曲面断层片中测得矫治前后第三磨牙萌出的各项评价指标变化量进行比较研究。结果:(1)第三磨牙萌出间隙及其与牙冠近远中径的比值变化量在3组之间均有统计学差异(P<0.05),拔第一磨牙组大于拔第一前磨牙组和非拔牙组。(2)上颌第三磨牙萌出角度变化量在3组之间均有统计学差异(P<0.05),拔第一磨牙组大于拔第一前磨牙组和非拔牙组;下颌第三磨牙萌出角度的改变量在各组之间没有统计学差异(P>0.05)。结论:上颌拔除第一磨牙矫治较常规矫治能明显增加第三磨牙的萌出间隙并改善其萌出角度;下颌拔除第一磨牙矫治较常规矫治能明显增加第三磨牙萌出间隙,而对于第三磨牙萌出角度3组间并无明显差异。

Objective：To observe the effects of first molar extraction on the eruption of third molar（M3）.Methods：30 cases of mandible and 20 cases of maxillas were divided into non-extraction,first premolar（4-extraction）and first molar extraction（6-extraction）groups respectively.The pretreatment and posttreatment panoramic radiographs were analysed.Changes in the third molar eruptive angle and space were compared among these groups.Results：1.There were significant differences in the change in the third molar eruptive space and space/width ratio among three groups（P〈0.05）.Space change in 6-extraction group was larger than that in 4-extraction group,and that in 4-extraction group was larger than non-extraction group.2.The eruptive angles of the mandible third molar were not significantly different among 6-extractiongroup,4-extraction group and non-extraction group;as for the maxilla third molar,the eruptive angles in 6-extraction group were increased more than that in 4-extraction group and non-extraction group.Conclusion：The maxilla first molar extraction can significantly advance the eruption space and angles of the third molar.The mandible first molar extraction can increase the third molar eruptive space,but has no effect on the eruption angles.