拔除第二恒磨牙后第三磨牙自行迁移的临床研究

Automatic drift of the third molar after the extraction of the second molar

目的 :探讨第二恒磨牙拔除后第三磨牙自行迁移在水平方向、垂直方向距离变化以及近中倾斜角的改变。方法 :将 2 6例患者分为实验组和对照组 ,实验组拔除第二恒磨牙的患者 15例 ,对照组未拔第二恒磨牙的患者 11例。 2组均拍摄侧位X线头影测量片 ,治疗前和治疗 9个月后测量第三磨牙在水平方向、垂直方向移动距离和近中倾斜度的变化并进行比较。结果 :实验组第三磨牙较对照组在水平方向 ( 7.0 8mm ,2 .0 9mm)移动较快 ,有显著差异 ;在垂直方向 ( 5 .75mm ,1.96mm)移动较快 ,有显著差异 ;其近中倾斜角变化 ( 11.2° ,3 .97°)也有显著意义。结论 :拔除第二恒磨牙加速了第三磨牙的萌出 ,减少了第三磨牙的阻生 ,并使第三磨牙尽快直立 ,并向近中迁移。

Objective:To investigate the third molar horizontal and vertical drift automatically after the second molar extraction.Methods: 26 patients,aged 11～18 years old, with the indications of second morlar extraction were divided into two groups:15 cases in experimental group with the extraction of the second molar and 11 in control group without the extraction. A cephalometric radiograph of each patient was traced on before and 9 months after treatment. Vertical and horizontal drift and mesio- angulation of the third molar were measured.Results:The third molar vertical mesio-movement (mm)in experimental and control groups was 7.08±2.04 and 2.09±0.47(P<0.05), horizontal 5.75±3.25 and 1.96±1.08(P<0.05), mesio-angulation decreased 11.2°±7.10°and 3.97°±1.72°(P<0.05),respectively. Conclusion:After second molar extraction, the rates of movement of the third molar in horizonal and vertical direction may increase; the mesio-angulation decrease permanently.