Yamabe K, Kouguchi M, Watanabe Y, Yamauchi K
Department of Orthodontics, Hiroshima University.
Nihon Kyosei Shika Gakkai Zasshi. 1990 Aug;49(4):302-13.
In the orthodontic practice, the first or second molars are extracted by reason of a necessity based on the treatment planning. In these cases, it is desirable that the third molar would be taken part in the masticatory function. This study was made to investigate the natural movement of the erupting third molars after the extraction of the first or second molar on the serial lateral cephalometric radiographs and orthopantomographs. Subjects were divided into three groups. The first is the group which the mandibular second molars were extracted. The second is the group which the first molars were extracted bringing about the successful eruption of the third molars. The third is the group which the first molars were extracted with resultant in the failure of the third molar eruption. In all cases, the orthodontic forces were not applied to the third molars. The results were as follows: 1. In the first group, all third molars were successfully erupted and a lot of the spaces after the extraction of second molars were utilized for the eruption of third molars. 2. In the second group, all third molars were successfully erupted and a lot of the spaces after the extraction of first molars were utilized for the mesial movement of the second molars. 3. In the third group, there were various patterns of the impaction of the third molars. It was suggested that the eruption of the third molar was related to the space distal to the second molar but it was not related to the anterio-posterior length of the mandibular body significantly.
在正畸治疗中，根据治疗计划的需要会拔除第一或第二磨牙。在这些情况下，希望第三磨牙能参与咀嚼功能。本研究旨在通过系列头颅侧位片和曲面断层片，调查第一或第二磨牙拔除后正在萌出的第三磨牙的自然移动情况。研究对象分为三组。第一组是拔除下颌第二磨牙的组。第二组是拔除第一磨牙后第三磨牙成功萌出的组。第三组是拔除第一磨牙后第三磨牙萌出失败的组。在所有病例中，均未对第三磨牙施加正畸力。结果如下：1. 在第一组中，所有第三磨牙均成功萌出，拔除第二磨牙后的许多间隙被用于第三磨牙的萌出。2. 在第二组中，所有第三磨牙均成功萌出，拔除第一磨牙后的许多间隙被用于第二磨牙的近中移动。3. 在第三组中，第三磨牙阻生有多种模式。提示第三磨牙的萌出与第二磨牙远中的间隙有关，但与下颌体的前后长度无显著关系。
