A Study of the Relationship between the Development of Skeletal Malocclusion and the Tooth Crowding in Posterior Part of Dentition

为了阐明后牙-义齿基托差异导致磨牙过度萌出与骨性错牙合的发生发展之间的关系，本研究利用猴子进行了一项模型实验。制作金属全冠，固定在实验动物左右上颌第一磨牙上，以增加牙合的垂直尺寸。在固定第一冠一个月后重复这一过程，总共增加了2 mm的垂直尺寸。生长动物表明，下颌骨的前移和髁突的生长与磨牙高度的增加有关。下颌骨的这种反应导致了咬合的前牙反牙合。然而，成年动物显示，下颌骨向后旋转是由于垂直尺寸的增加，提供了前牙合开牙合。这些结果提示，磨牙后牙差过大是导致骨性错牙合，如骨性III类错牙合和骨性开牙合的重要原因之一。

In order to clarify the relationship between the development of skeletal malocclusion and the over eruption of molars due to posterior tooth -to-denture base discrepancy, a model experiment using monkeys have done in this study. Metal crowns were made and fixed on the right and left maxillary first molars of experimental animals to increase the vertical dimension of occlusion. This procedure was duplicated after one month of fixing the first crown and providing the increasing 2mm of the vertical dimension totally.Growing animal indicated that the forward displacement of the mandible followed by the condylar growth was associated with increasing the molar height. This response of the mandible induced the anterior cross bite of occlusion. However, adult animal showed that the backward rotation of mandible was induced by the increasing vertical dimension, providing the anterior open bite occlusion. These findings are suggesting that the molar over eruption due to posterior discrepancy is one of the important etiologic factors in the development of skeletal malocclusion such as skeletal class III and skeletal open bite.