下颌前方牙列缺失修复前后牙根尖应力分布的光弹实验

目的：探讨前牙以及前牙并前磨牙缺失修复前后对下颌牙根尖应力分布规律的影响。方法：用环氧树脂制作正常牙合]、前牙缺失、前牙并前磨牙缺失的下颌光弹模型，并在翻制好的模型上进行常规活动义齿修复。2．0kg垂直加载后，在光弹仪上对牙根尖和牙槽嵴中相应观测点的主应力大小和方向进行观测。结果：前牙缺失以及前牙并前磨牙缺失后，余留牙根尖主应力方向偏远中颊侧的程度加大，而且随着缺牙范围由前向后的逐渐增大，这种变化趋势也愈加明显。义齿修复后，整体牙列的根尖主应力方向与正常牙合]相比没有差异，但在局部义齿修复区域的牙槽嵴相应观测点上，主应力方向与正常相比更偏向近中舌侧。无论是前牙缺失或者前牙并前磨牙缺失，余留牙的承力水平在义齿修复前明显高于正常牙合]各牙，在义齿修复后承力水平回落至与正常牙合]无差别的状态。但在义断修复的区域其应力水平仍较正常牙合]相应位置稍低。结论：前牙或前牙并前磨牙缺失会对下颌余留牙根尖主应力的大小及方向造成显著影响，牙槽嵴对咬合力沿下颌骨向后方的传导特征也会随之发生改变，而活动义曲修复后这种影响可以部分消除。

Photoelastic analysis of apical stress distribution in the occlusion with loss of partial anterior teeth before and after restoration

AIM:To investigate the effects of anterior teeth or anterior teeth and premolars loss to the apical stress di stribution before and after restoration.METHODS:Epoxy resin models of normal and anterior teeth loss occlusion were employed to determine the stress distribution in apical area.After being loaded with 2.0kg vertical weight,the values and directions of principle stress in the observed area before and after restoration were measured by photoelastic apparatus.RESULTS:No matter in both anterior teeth loss occlusion or in anterior teeth and premolars loss occlusion,the main stress of the remaining teeth directed more distal-buccally from median than that of normal occlusion.And with the increase of teeth-loss range from anterior part to posterior part,the variation trend of main stress directions showed more distinctly.After restoration of losing teeth,the main stress directions of the whole dentition showed no difference with the normal occlusion while that of alveolar ridge under restoration area directed more mesial-lingually than that of normal occlusion.The main stress values in the remaining teeth of both teeth-loss occlusions were much higher than that of normal occlusion and decreased back to the normal level after restoration.But in alveolar ridge under restoration area,the main stress values were still lower than that of normal level.CONCLUSION:Anterior teeth loss or anterior teeth and premolars loss could effectively influence the apical stress distribution and the occlusal force transferring feature.The character of force conduction of the alveolar bone along the mandible to temporomandibular joint could also be changed.The restoration of losing teeth could partly eliminate the effects.