下颌第二磨牙在牙弓后段中扮演重要角色，由于受到第三磨牙以及牙弓后段拥挤等多重因素的影响，其阻生受到广泛关注。下颌第二磨牙阻生常表现为近中阻生，影响咀嚼效率，与下颌第一磨牙邻接不良而继发龋病、牙周病及牙根吸收。由于下颌第二磨牙位于牙弓末端，传统正畸治疗方法难以施加矫治力，是正畸治疗的难点。本文就其病因及正畸治疗进展做一综述。“,”The mandibular second molars play an important role in the posterior segment of the dental arch. Due to the influence of multiple factors, such as the mandibular third molars and the crowding in the posterior segment of the dental arch, the impaction of mandibular second molar have been widely concerned. The impacted mandibular second molars are usually presented as mesial impaction, which reduce masticatory efficiency andcause some problems such as caries, periodontitis and root resorption of the adjacent molars. The impacted mandibular second molars are difficult to manage by traditional orthodontic methods, because it is located at the end of the dental arch. This review focuses on the impaction etiology and the progress of its orthodontic treatment.