Smith R
Basingstoke District Hospital.
Br J Orthod. 1996 May;23(2):109-14. doi: 10.1179/bjo.23.2.109.
There is some controversy over whether the extraction of upper second permanent molars as part of orthodontic treatment leads to the over eruption of unopposed lower second permenent molars. A study was established to investigate the presence of any over-eruption in a group of subjects who had upper second permanent molars extracted as part of a previous course of orthodontic treatment. These subjects (the experimental group) were compared with a control group of subjects, matched for age and sex. Upper and lower impressions were taken, and the vertical positions of the posterior teeth were objectively assessed from the study models using the travelling microscope. Measurements from the study models showed that the distal aspect of the lower second permanent molar had over erupted in the experimental group when compared to the control (P < 0.001 right, P < 0.05 left). The degree of over-eruption was influenced on the mesial aspect by the distal position of the upper first permanent molar (P < 0.01), but the distal aspect was not. Eruption of the upper third molar did not affect the over-eruption of the lower second permanent molar in the experimental group. The majority of upper third molars had erupted at least 3 years since the upper second molars had been extracted, but the majority had erupted into an unfavourable contact position with the first permanent molar.
作为正畸治疗的一部分，拔除上颌第二恒磨牙是否会导致未萌出的下颌第二恒磨牙过度萌出存在一些争议。一项研究旨在调查一组作为先前正畸治疗过程一部分而拔除上颌第二恒磨牙的受试者中是否存在过度萌出情况。将这些受试者（实验组）与年龄和性别匹配的对照组受试者进行比较。采集上下颌印模，并使用移动显微镜从研究模型中客观评估后牙的垂直位置。研究模型的测量结果表明，与对照组相比，实验组下颌第二恒磨牙的远中面出现了过度萌出（右侧P<0.001，左侧P<0.05）。过度萌出的程度在近中面受上颌第一恒磨牙远中位置的影响（P<0.01），但在远中面不受影响。上颌第三磨牙的萌出并未影响实验组下颌第二恒磨牙的过度萌出。大多数上颌第三磨牙在拔除上颌第二磨牙后至少已萌出3年，但大多数萌出到与第一恒磨牙不利的接触位置。
