[Removal or retention of nonimpacted third molars].

Nonimpacted third molars (N-M3s) refer to the third molars (M3s) that completely erupt and reach the occlusal plane without rotation. Although the removal of unerupted M3s in young adults is generally approved by most dentists, the decision on removal or retention of N-M3s remains challenging as a result of unawareness of the potential harm of N-M3s. Recent studies suggested that N-M3s were associated with deteriorated effects to the health of adjacent teeth, including higher risks of caries and alveolar bone resorption. Therefore, regular monitoring and early clinical decision on N-M3s are essential to reduce the risks of adverse effects on adjacent teeth. This review is structure to give a comprehensive overview of the negative impact of N-M3s to the adjacent teeth, in order to provide rational guidelines for clinical decision-making of N-M3s.非阻生第三磨牙（nonimpacted third molars，N-M3s）是指萌出到达（牙合）平面且无明显扭转的第三磨牙（third molars，M3s）。虽然口腔医师多认同阻生第三磨牙（impacted third molars，I-M3s）应尽早拔除，但N-M3s的“拔”与“留”却尚存诸多争议，其原因主要是口腔医师和民众普遍对N-M3s可能带来的危害认识不足。现有证据表明，N-M3s相邻的第二磨牙（second molars，M2s）远中龋和牙周病的发生率均显著高于M3s缺如的M2s。因此，N-M3s的定期监测和早期决策对减少其邻牙M2s患病风险至关重要。本文重点阐述N-M3s对邻牙M2s的危害，并对N-M3s的临床决策给出参考建议，以期丰富和完善口腔医师对N-M3s的认识，进而引起医师和民众对N-M3s的共同重视与关注。.