正畸治疗中磨牙的拔除和保留(五十)——减数第一或第二磨牙后发育期第三磨牙牙轴调整随访研究

The follow-up study of puberty third molar's axis inclination adjustment after extraction of first or second molar

目的:通过对减数第一(M1)或第二磨牙(M2)矫治后牙根未发育完成的第三磨牙(M3)在萌出建过程中牙轴倾斜度调整的随访研究,探讨减数磨牙对第三磨牙牙轴自我调整的影响。方法:共选择减数M1或M2进行矫治病例31例,初诊年龄平均13.5岁,矫治结束时年龄平均15.5岁,随访时年龄平均19岁;所有病例均采用直丝弓矫治器矫治。分别对矫治前(T1)、矫治结束(T2)、随访时(T3)的第三磨牙有关线距及牙轴倾斜度测量值进行分析。结果:矫治结束与随访时的磨牙后间隙均大于M3宽度,矫治前的磨牙后间隙小于M3宽度,结果有显著性差异;矫治结束与随访时的上颌M3牙轴倾斜度较矫治前显著增大,但随访时与矫治结束时相比无显著性差异;矫治结束与随访时的M3与M2(M1)牙轴夹角的绝对值及下颌M3牙轴倾斜度较矫治前显著减小,但随访时与矫治结束时相比无显著性差异;其余测量项目均无显著性差异。结论:经减数第一或第二磨牙后,为第三磨牙提供了足够的萌出间隙,这就为第三磨牙的自我调整提供了前提条件。第三磨牙的牙轴倾斜度在矫治期完成了大部分的调整,其牙体长轴与近中磨牙牙体长轴逐渐趋于平行,有利于第三磨牙萌出后发挥正常咀嚼功能,避免牙周损伤。

Objective:To study impaction of molar extraction on puberty third molar's axis inclination adjustment through follow-up investigation. Method:31 cases were selected whose mean age of before treatment were 13.5 years,mean age of after treatment were 15.5 years,and mean age of follow-up time were 19 years. All cases were treated with straight wire appliance. Respectively,measurement analysis of third molar was made in three period,before treatment(T1),end of treatment (T2),follow-up time (T3). Result:Molar posterior spaces were significantly larger than M3's width in T2 and T3 and smaller than M3's width in T1. Upper M3's axis inclinations in T2 and T3 were significantly larger than in T1. Absolute of M3 and M2 (M1)axis angles and lower M3 axis inclinations in T2 and T3 were significantly smaller than in T1. The rest of measurements was no significant difference. Conclusion:Extraction of first or second molar provides sufficient spaces for third molar's eruption,which is the preconditions for self-adjustment. Third molar's axis inclinations complete most of the adjustments in the treatment time and become more parallel to anterior molars,which is help for third molar's chewing function and prevention of periodontal injury.