正畸治疗中拔除第二恒磨牙对第三磨牙萌出位置影响分析

Clinical analysis on eruption of third molars after extraction of second molars

目的观察在正畸治疗中拔除第二恒磨牙后,第三磨牙的萌出情况,它在水平和垂直方向上的移动距离,以及与平面之间的倾斜角度,为临床工作提供参考。方法实验组观察19名患者,共34颗第二磨牙被拔除,其中上颌20颗,下颌14颗。未拔牙侧作为对照组,共38颗第三磨牙,16颗上颌,22颗下颌。所有病例均拍摄拔牙前及一年后全颌曲面体层片,测量第三磨牙在水平、垂直和倾斜角方面的变化,计算第三磨牙移动的实际距离。结果实验组34颗第三磨牙,在一年内均有不同程度萌出,其中上颌第三磨牙平均在水平方向移动8.41mm,在垂直方向移动7.41mm,直立16.45°下颌第三磨牙平均在水平方向移动6.77mm,在垂直方向移动4.021mm,直立7.14°和对照组相比,具有显著性差异。结论①拔除第二磨牙后,第三磨牙萌出加速,阻生减少;②上颌第三磨牙的移动快于下颌第三磨牙,其萌出的各项指标也好于下颌。

Objective This retrospective study was conducted to assess the eruption of third molars after extracrtion of second permanent molars by using panoramic radiographs. Methods The subjects were 19 patients who had 34 permanent second molars extracted during or before orthodontic treatment. The position of the third molars was assessed from panoramic radiographs taken before second-molar extraction and 1year after extraction. Vertical and horizontal drift and angulation of the third molars were measured. Another 38 third molars in the unextract side were choosen as control group. Changes in third molar position from pretreatment to posttreatment between two groups were compared. Results 34 third molars of experimental group all erupted in different degree. Horizontal and vertical distances the maxillary third molars moved was in an average of 8. 41 mm and 7. 41 mm,the uprighted angulation in maxillary was average 16. 45°,The data in mandibular third molars were 6. 77 mm,4. 021 mm,and 7. 14°mm。It showed more vertical movement and more upright of the third molars in maxillary. Conclusion ①Our results suggest that second molar extraction may increase the rate of eruption of the third molars,and at the meanwhile decrease there impaction. ②The movement of maxillary third molars was faster than mandibular,it was seems that its positions were also better than that in mandibular third molars.