四种修复设计对下颌第一磨牙远中残根应力的影响

目的研究不同修复设计对下颌第一磨牙远中残根应力的影响，筛选出最佳的修复方案。方法用有限元和光弹应力分析方法，模拟6近中根拔除，远中根保留，分别采用6单冠、67联冠、56联冠、567联冠修复，比较相同载荷条件下6远中根的应力状况。结果与正常6的牙周应力相比，6远中根在6单冠修复时应力增大3倍以上，67联冠修复时应力增为两倍左右，56联冠和567联冠修复时应力均接近正常值。结论6远中残根可采用56联冠和567联冠修复。

Stress analysis of different fixed prosthesis designs following molar hemisection therapy

Objective To evaluate mechanical behavior of different fixed prosthesis following molar hemisection therapy for clinical reference. Methods Finite element method and photoelastic method were employed to investigate the stress distribution around the reserved distal root of the first mandibular molar with various fixed prosthesis designs. The restorations of single crown of the first mandibular molar, combined crowns of the first and second mandibular molars, combined crowns of the second mandibular premolar and first mandibular molar, and combined crowns of the second mandibular premolar, the first and second mandibular molars were designed. The same load was simulated on the occlusal surfaces of the molars. Results The results of two studies showed that the stress around the reserved root in the single crown model was over 3 times as much as that of the normal model, the first mandibualr molar with normal roots and a crown. For the combined crowns of the first and second mandibular molars, the stress was almost twice of the normal stress. While in the models of the combined crowns of the second mandibular premolar and first mandibular molar, as well as the combined crowns of the second mandibular premolar, the first and second mandibular molars, the stress distributions were similar to that in normal conditions. Conclusions Both the results indicated that the restoration of two-unit dual-ended combined crowns has favorable stress distribution and is applicable for the reserved root following the hemisection therapy.