[摘要] 目的：3年随防观察近中阻生的下颌第三磨牙萌出情况与其倾斜角度的关系。方法：72名在校本科生，年龄18~20岁，共108颗近中阻生的下颌第三磨牙,研究开始和观察3年后分别拍摄全颌曲面断层片，检查下颌第三磨牙倾斜程度和萌出水平。结果：在3年观察结束时,71.4%(30/42)最初倾斜角度在5°~10°之间的下颌第三磨牙变为直立。33.3%(6/18)最初倾斜角度在15°~20°之间的下颌第三磨牙变为直立。25%(3/12)最初倾斜角度在25°~30°之间的下颌第三磨牙变为直立。最初倾斜角度在35°及以上的下颌第三磨牙没有一颗变为直立的。结论：在一定程度上，可以根据阻生的下颌第三磨牙近中倾斜的角度来预测第三磨牙日后的萌出状况。有些近中阻生，倾斜角度小于35°的下颌第三磨牙经过一定时间是有可能完全萌出而不必预防性拔除的。

    [关键词] 近中阻生的下颌第三磨牙 阻生角度 萌出水平

    The Relationship between Angular Position and Eruption Status of Mesially Impacted Mandibular Third Molars.

    XIA Yong-hua, SHANG Shu-huan, LI Cheng-zhang.

    School of Stomatology，Harbin Medical University, Harbin 150001

    [Abstract]Objective: To measure changes in angular position and eruption status of mesially impacted mandibular third molars (M3) during 3-year follow-up period. Method: Standardized panoramic radiographs were taken at the start and at the end of 3 years’ study for seventy two college students (their ages were from 18 to 20). Angulation and degree of impaction of M3 were determined by their sagittal relationships to the adjacent second molars. One hundred and eight impacted M3 were either partially erupted or unerupted. Results: After 3 years, the proportion of M3 that became upright (zero tilt) was 71.4% (30/42) with initial angulations of 5 to 10 degrees, 33.3(6/18) with initial angulations of 15 to 20 degrees, and 25% (3/12) with initial angulations of 25 to 30 degrees. None of the M3 originally presented at 35 degrees or more became upright. Conclusion: According to the angular position of M3, its eruption status could be forecasted to some extent. A significant proportion of mesially impacted mandibular M3 with initial angulations less than 35 degrees could change their angulation and become fully erupted. It is not necessary to prophylactically remove all impacted mandibular third molars. ......