Abstract:

Stability is one of the main goals of orthodontic treatment and the prerequisite to maintain the achieved outcomes. As the foundation of an ideal occlusal relationship，posttreatment movement of upper first molar gives rise to instability of the entire dentition and alignment，still it happens to some extent on account of continuous growth，age related changes and the tendency of relapse，in spite that various retention strategies have been adopted. This paper made a review of the changes of upper first molar’s location in three dimensions during the postretention period and the probable causes.

Key words: upper first molar, three -dimensional, stability, retention

摘要：

正畸治疗后的牙列稳定性是治疗的基本目标之一，也是保持治疗成果的前提。上颌第一磨牙是理想牙牙合关系的基石，其位置和轴倾度变化将会引起整体牙牙合关系的变化和牙齿排列的不稳定。保持期间受持续的生长发育、增龄性变化及正畸后复发趋势等因素影响，上颌第一磨牙位置在横向、矢状向和垂直向仍在发生不同程度的改变。以下就近年来针对保持期上颌第一磨牙在三维方向上的位置变化趋势及相关原因分析的研究结果做一综述。

关键词: 上颌第一磨牙, 三维方向, 稳定性, 保持期