Richardson M, Mills K
Department of Orthodontics, School of Dentistry, Royal Victoria Hospital, Belfast, Northern Ireland.
Am J Orthod Dentofacial Orthop. 1990 Sep;98(3):242-6. doi: 10.1016/S0889-5406(05)81601-4.
Mesial drift and change in crowding over a 5-year period were compared in 30 subjects whose lower second molars were extracted between ages 11 and 17 years and 30 subjects whose lower second molars were not extracted. Significant differences were found. The nonextraction subjects showed an average forward movement of first molars and an increase in crowding. The extraction group showed slight distal movement of first molars and a decrease in crowding. It is concluded that lower second molar extraction reduces the tendency to forward movement of buccal segments and increased crowding by relieving eruptive pressure from third molars and that the presence of a developing lower third molar with insufficient space can be one cause of late lower arch crowding.
对30名在11至17岁之间拔除下颌第二磨牙的受试者和30名未拔除下颌第二磨牙的受试者，比较了5年期间的近中移动和牙列拥挤变化。发现了显著差异。未拔牙的受试者表现出第一磨牙平均向前移动且牙列拥挤增加。拔牙组表现出第一磨牙轻微向远中移动且牙列拥挤减少。得出的结论是，拔除下颌第二磨牙可减轻第三磨牙的萌出压力，从而降低颊侧牙段向前移动的趋势并减少牙列拥挤增加，并且存在发育中的下颌第三磨牙且空间不足可能是下颌牙弓后期拥挤的一个原因。
