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目的 对比分析拔除 4个第一前磨牙或第二前磨牙后上颌牙弓的变化。方法 随机选择 5 0例拔牙矫治病例。其中减数第一前磨牙 3 0例、减数第二前磨牙 2 0例。通过X线头影测量对比分析治疗前后牙牙合的变化。结果 无论是减数第一前磨牙组或是减数第二前磨牙组 ,其矢状方向长度变化相似。但减数第一前磨牙组比减数第二前磨牙组前牙内收更多。结论 应根据对切牙内收或磨牙前移的预期来决定减数第一前磨牙或第二前磨牙
Objective To compare and analyze the changes of maxillary dental arch after removal of 4 first premolar or second premolar. Methods 50 cases of tooth extraction were randomly selected. Among them, the first premolar 30 cases and the second premolar 20 cases. The changes of occlusal changes before and after treatment were analyzed by X-cephalometry. Results Both the first premolar group or the second premolar group showed similar changes in sagittal direction length. However, the first premolar molar group than the second premolar group anterior adduction more. Conclusions The number of first premolar or second premolar should be determined on the basis of the anticipation of incisor adduction or molars advancement