正畸拔除第一前磨牙对第三磨牙萌出角度的影响

目的：研究正畸拔除第一前磨牙对第三磨牙的影响。方法：37例第一前磨牙拔除和33例非拔牙患者作为研究对象,拍摄术前术后的全景片,测量第三磨牙长轴与平面及第三磨牙长轴与第二磨牙长轴的夹角,对治疗前后夹角的变化以U检验进行比较。结果：结果显示,拔除第一前磨牙后,下颌第三磨牙的的萌出角度得到了改善,而对上颌第三磨牙萌出改善并不明显。结论：拔除下颌第一前磨牙后,第三磨牙萌出角度会更加直立,从而可能减少其阻生的可能性。

Impact of First Premolar Extractions in Orthodontic Treatment Upon Third Molar Eruptions Angle.

Objective:The purpose of this study was to determine the relationship between the inclinations of second and third molars during a 2 to 2.5 year period in patients treated orthodontically with and without premolar extractions.Methods:Records of 37 first premolar extraction patients and 33 nonextraction patients were examined.The pretreatment and posttreatment panoramic radiographs were analyzed.The angles were measured between the long axis of the third molar and the occlusal plane and between the long axis of the third molar and the long axis of the second molar.Changes in third molar angulations from pretreatment to posttreatment for two groups were compared by Mann-Whitney U-test.Results:Statistical analysis revealed that mandibular third molars showed an improvement in angulation relative to the occlusal plane in the first premolar extraction group.Conclusion:With the premolar extractions,the third molar eruption will be more vertical angle,which may reduce its impacted possibilities.