[Three-dimensional finite element analysis of the stress distribution of bone tissue around porous titanium implant].

Objective: To analyze the stress distribution of different types of bone tissue around porous titanium implant in different mechanical loads and to further evaluate the biomechanical properties of porous titanium implant. Methods: Finite element (FE) models of implant restorations for the maxillary first premolar was established, and the diameter of implants in the models was 4.1 mm. Five models was constructed according to diameter of implant central pillar and the thickness of outer porosity: solid group (group A), central pillar 1.5 and 3.1 mm and outer porosity 30% (group B and C), central pillar 1.5 and 3.1 mm and outer porosity 40% (group D and E). Different loads (150 N vertical force, 50 N lateral force) were applied to the occlusal surface of implant restorations in type Ⅲ bone and maximal von Mises stress was evaluated. Meanwhile, a couple of simplified maxillary part models varied in four types of bone were constructed with the implants bearing load of simulation ultimate force to evaluate the stress distribution of different types of bone. Results: With different mechanical loading, the stress value of bone tissue around porous implant (group B-E) was greater than that in the solid structure (group A). Under the load of simulation ultimate force, the maximum stress of the bone rised with the increase of porosity and thickness of the porous implant. And the maximum stress value of the surrounding bone tissue changed with the change of bone. Under vertical loading, the maximal von Mises stress of the bone around solid implants of group A was 17.56 MPa, which was a little lower than that of group B and C. And the maximal equivalent von Mises stress of group D and E was 69.24 MPa. The results of lateral force and simulation ultimate force loading were similar. The stress of the bone tissue around implant increased with the decrease of bone quality. The maximum stress value of group D implant was 134.95 MPa. Conclusions: Porous structure of the implant is conducive to transmit stress to surrounding bone tissue and increases the mechanical stimulation of bone. However, if the value and direction of load are inappropriate or quality of bone is poor, pathological stress may be produced.目的： 分析内芯致密外层不同孔隙率结构的钛种植体周围骨组织应力分布情况，评估多孔结构钛种植体的生物力学性能。 方法： 建立5组直径为4.1 mm的种植体三维有限元模型：实心（A组）、外层孔隙率为30%中央实心支柱直径分别为1.5和3.1 mm（B和C组）、外层孔隙率为40%中央实心支柱直径分别为1.5和3.1 mm（D和E组）；同时建立4类骨组织、上颌第一前磨牙牙冠、基台模型。将5组种植体装配于Ⅲ类骨组织中，分别施加150 N垂直和50 N侧向载荷；将5组种植体分别装配于4类骨组织中，加载极限■力载荷；分析种植体及周围骨组织von Mises应力分布。 结果： 各种载荷条件下B~E组多孔结构钛种植体骨界面最大von Mises应力均大于A组。极限■力载荷下，随着种植体多孔层厚度和孔隙率的增加，以及骨组织质量的降低，骨组织的最大von Mises应力增加。在Ⅲ类骨中垂直加载时A组最大von Mises应力为17.56 MPa，B、C组种植体最大von Mises应力较A组大，D、E组进一步增大，可达69.24 MPa；侧向载荷、极限■力载荷下结果相似。同组种植体周围骨应力随骨组织质量降低而增加，D组种植体周围骨组织最大von Mises应力可达134.95 MPa。 结论： 种植体的多孔结构有利于应力向周围骨组织传导，可增加骨组织受到的力学刺激，但若■力大小、方向不当，或骨组织质量不佳，则多孔结构种植体可能产生病理性应力。.