661例正畸患者第三磨牙发育的X线研究

The X-ray Study of the Third Molars in 661 Orthodontic Patients.

目的 :研究青少年第三磨牙发育程度及萌出方向。方法 :通过对全颌曲面断层片的观察将 6 6 1例正畸患者第三磨牙牙胚发育程度分级。结果 :6岁时男女均无M3牙胚出现 ,女孩第三磨牙发育比男孩早 ,下颌比上颌早 ;萌出方向下颌近中倾斜向出现率高 ,上颌远中倾斜向出现率高。结论 :错牙合畸形的发生与第三磨牙发育的关系密切 。

Objective:To study the erupt direction and development of the third molars of the ado lescents.Methods:The development degree of the third molars in 661 was divided into three phrases by panoramicgraph.Results:There is no M3 germs in 6-year-old children.The development of M3 appears earlier in girls than in boys,and earlier in the mandible than in the maxillary.The erupt direction appears mesial tilting in the mandible and distal tilting in maxillary more frequently.Conclusions:The development of third molar and malocclusion has very close relationship.