部分后牙缺失修复前后下颌牙根尖应力分布的光弹实验研究

目的：探对部分后牙缺必修复前后对下领牙根尖应力分布规律的影响。材料和方法：以环氧树脂制作正常[牙合]及单侧、双侧后牙缺尖的下颌光弹模型，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及牙槽嵴中相应观测点的主应力大小和方向进行观测。结果：单侧磨牙缺失时，缺牙对侧和缺牙侧余留牙的根尖主应力水平升高、缺牙侧余留牙根尖主应力的远中偏向角度减小，从而使余留牙的负担明显增大；和义齿修复后缺牙对侧牙和缺牙侧余留牙的根尖主应力水平明显回落至正常，但义齿修复区域牙槽嵴所承受的远中颊侧的力明显增大，而且缺牙对侧余留牙的应力水平明显高于义齿修复侧相应的牙槽嵴观测点。当双侧下颌磨牙同时缺失时，余留牙的根尖主应力明显比正常更偏向近中舌侧，而且其上的应力水平电异常增高；活动义齿修复后，余留牙上的应力水平回落至正常水平．义齿修复区的应力水平更低，而且余留牙及义齿修复区的牙槽嵴承力向远中颊侧的分量更大。结论：单侧或双侧磨牙缺失会对下颌牙余留牙根尖主应力的大小及方向造成显著影响，而活动义齿修复后这种影响可以部分消除，但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。

Photoelastic Analysis of Apical Stress Distribution in the Occlusion with Loss of Partial Posterior Teeth Before and After Restoration

Objective: To in vestigate the effects of partial posterior teeth loss to the apical stress distribution before and after restoration. Method: Epoxy resin models of normal and unilateral or bilateral mandibular molars 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. Result: In unilateral molars loss occlusion, the main stress values of the remaining teeth in teeth-losing side and those in opposite side increased distinctly and the main stress direction of the remaining teeth in teeth-losing side directed more medially than those of the normal occlusion, which means that the remaining teeth of unilateral molars loss occlusion would bear more weight than the teeth of normal occlusion. After the restoration of losing teeth, , the main stress values of the remaining teeth in teeth-losing side and those in opposite side decreased back to the normal level. However, the distal-buccal components of forces in the alveolar ridge under restoration area increased obviously and the main stress values of the teeth in the side opposite side showed higher than that of observed area in the alveolar ridge under restoration area.In bilateral molars loss occlusion, the main stress of the remaining teeth directed more mesial-lingually than that of the normal occlusion and the main stress values also increased abnormally. After the restoration, the main stress values decreased back to the normal level and that of restoration area showed even lower. And the distal-buccal components of forces in the remaining teeth and alveolar ridge under restoration area both increased obviously. Conclusion: Unilateral or bilateral molars loss could effectively influence the apical stress distribution and the restoration of losing teeth could partly eliminate the effects. At the same time, the occlusal force transferring feature of alveolar bone along the mandible to temporomandibular joint could also be changed after the restoration.