从曲面体层片观察第一恒磨牙萌出的图像特征

The eruption characteristic of first permanent molar studied by panoramic radiographs

目的:通过曲面体层片(PR)描述非异位萌出的第一恒磨牙萌出过程中在影像片中的变化特点。方法:纳入5～10岁青少年及儿童所拍摄的573张PR,测量计算第一恒磨牙倾斜角度、水平垂直距离比值。将所得数据进行统计分析绘制随年龄变化折线图。结果:上颌第一恒磨牙倾斜角度随年龄增加而降低,变化范围为115°～97°,水平向距离比值逐渐降低,从0. 45～0. 42,男性变化范围稍小于女性;下颌第一恒磨牙倾斜角度随年龄增加而逐渐增加,范围为66°～73°,水平向距离比值均随年龄增加而逐渐降低,下颌变化范围为0. 65～0. 55,且下降速度快于上颌。结论:5～10岁儿童上颌第一恒磨牙萌出过程中牙体倾斜角度随年龄增加而减小,下颌第一恒磨牙倾斜角度随年龄增加而逐渐增大;第一恒磨牙牙胚在萌出过程中逐渐向牙合方及近中移动。

Objective:To study the eruption characteristic of none-ectopic erupted first molar in the 5-10 year-old children by panoramic radiographs(PR).Methods:The inclination angle and horizontal vertical distance ratio of the first molars of the children were measured by PR.Line charts were drawn and the median degree of inclination angle of different age groups were analyzed.Results:The inclination angle of the maxillary first permanent molar decreased with the increase of age from 115°to 97°;the horizontal distance ratio reduced gradually from 0.45 to 0.42 and the range of the male was slightly less than that of the female.Mandibular first permanent molar inclination angle increased with the increase of age,ranging from 66°to 73°;the horizontal distance ratio decreased from 0.65 to 0.55 with the increase of age and mandibular teeth ratio decreased faster than maxillary teeth.Conclusion:The maxillary first molars inclination angle decreases with the increase of age and mandibular first molar inclination angle has the opposite change.As for the development,the first molar germ moves towards occlusion plane and mesio-occlusion.