快速上颌扩大前后变化的三维x线头影测量研究

A STUDY ON THE THREE-DIMENSIONAL CEPHALOMETRIC CHANGES AFTER RAPID MAXILLARY EXPANSION

目的 :探讨快速上颌扩大所引起的颅面牙三维的变化。方法 :采用三维x线头影测量系统对 30例RME的患者快扩前后的头颅正、侧位片进行立体整合 ,空间测量分析。结果 :上颌面角增加 ;下颌B点后移 ;SNB角减少 ;面高显著性增长 ;覆变浅 ;上中切牙冠间出现了明显间隙 ,并大于根尖增宽间距 ;上下颌第一磨牙间距明显增宽。结论 :在冠状面与水平面上左右上颌骨间骨缝呈三角形打开 ,上下颌均表现出向下向后的旋转趋势 ,上颌牙弓的增宽量中不但有骨性扩大还包括了牙槽嵴与牙齿的倾斜。

Objective:To investigate the cephalometic changes after rapid maxillary expansion in three dimensional space.Methods:Thirty juvenile subjects were evaluated.Hyrax expansion appliacese were used for all cases.Lateral and posteroanterior cephalometric films were taken before and immediately after treatment.Through the three dimension cephalometry system,the space position of each landmark was established in order to get the true value of each variable.The results were compared.Results:Maxillary facial angle increased.The point B in mandible was repositioned more posteriorly.The facial heights increased significantly.Overbite got lighter.The upper central incisors were laterally separated and the crowns moved further laterally than the root apices.The intermolar distances of maxillary and mandible were increased.Conclusion:The palatal suture split in a triangular fashion in the frontal and the coronal plane.The maxillary and mandible displayed a downward and backward rotation in the palate plane.Arch expansion was made up of not only suture separation but also tooth tipping,tooth displacement and alveolar process tipping and bending.