关键词: 磨牙近中移动, 第一磨牙缺失, 微种植体支抗, 正畸治疗, 间隙关闭

Abstract: First molar missing or extraction is common in orthodontic clinic，and the protraction of the second molar to close the space of the missing tooth is an important method to replace the missing tooth and to maintain the occlusal function. However，many factors，such as patients′ age，tooth tilt angle and periodontal condition，should be taken into consideration during the second molar protraction. Besides，doctors should try to avoid the risk of alveolar bone and root absorption. Due to the strong anchorage effect of second molar，more rigorous anchorage design and effective support are needed. This review summarizes the indications，protraction method and risks，aming to provide clinical reference for the orthodontic treatment for closing the space of first molar missing or extraction by second molar protraction.

Key words: molar protraction, first molar missing, mini-implant anchorage, orthodontic treatment, space closure