下颌第一磨牙不同冠根比种植修复体的三维有限元分析

背景：为了尽量避免种植义齿修复时出现种植体周围骨组织应力集中。以往有研究应用增大种植体与骨界面的结合面积、增加直径、增加长度等方法以期使种植体骨界面应力分布更趋均匀，以提供更大的支持力，但观察时间较短，且临床报告并不一致。目的：设计不同冠根比种植修复体，采用三维有限元法，对轴向加载和颊舌向加载下的不同冠根比种植修复体周围骨组织应力分布进行分析，以求找到适合临床种植修复的冠根比范围。方法：应用CT断层扫描技术得到下锁骨和下颌牙列的大致轮廓，通过交互式的医学影像控制系统对图形特征进行整体图像拟合，再以计算机软件生成云图，根据云图的数据进行三维重建，从而得到包括下颌骨和下颌牙列的三维有限元模型：运用几何模型方法建立不同冠根比种植修复下颌第一磨牙的三维模型。运用Hyperwork8.0及Ansys11.O大型有限元分析软件，建立下颌不同冠根比的种植修复体模型，并完成牙冠的修复。在模拟黔向载荷的基础上，比较不同冠根比种植修复体周围骨组织应力分布状况。结果与结论：获得了下颌骨及下颌牙列的三维有限元模型，以及下颌不同冠根比种植修复体的有限元模型。通过对不同冠根比种植体施加轴向100N及烦舌向50N的力，种植体周围骨组织产生的应力分布状况比较发现，颊舌向受力下种植体颈部及周围骨皮质为应力集中区；轴向施力时种植体颈部、根尖部周围的骨组织为应力集中区。

Three-dimensional finite element analysis of implants with different crown-to-root ratio for the mandibular first molar

BACKGROUND： Mandibular first molar is clinically more common oral diseases. Clinically, the first molar for a variety of repair methods, compared to the traditional fixed bridge, implant because of their chewing efficiency, less damage to the adjacent teeth and gradually began to widely adopt. Ability to support the implant is designed to be taken into account, together with the supporting tissue implant into a mechanical exercise load to bear chewing function structure, this structure is not destroyed to achieve long-term stability to function, must be consistent with biomechanical principles. OBJECTIVE： Dentition lack is one of common oral diseases, it has become an important oral developed direction by planting repair to restore missing teeth by common methods of cultivation including a single implant repair and crown a single fixed bridge repair and so on. Different cap ratios of restoration implants have become an important factor influencing the long-term effects for restoration implants. Therefore, through CT scan this issue made two solid models by computer, which embrace normal human mandible and mandibular dentition three-dimensionally. And on the basis of solid models, it generated finite element models by large-scale finite element analysis software. We compared the stress distribution of implants of different crown-to-root ratios. Thus, it laid the theoretical foundation for the lack of clinical dental restoration. METHODS： This issue acquired general outline of the mandible and mandibular dentition by CT technology. It fitted overall image according to graphics features by picture control system, and then generated cloud chart by computer software. We proceed three-dimensional reconstruction according to the cloud chart, as a result, we gained three-dimensional finite element models of mandible and mandibular dentition. Moreover, we established three-dimensional models of two-highest single-root implants to repair the mandibular first molar. To apply Hyperwprk8.0 and Ansysl 1.0, we established mandibular implant prosthesis models of different crown-to-root ratio implants, and finished the crown restoration. On the basis of the simulated same direction load, we compared the stress distribution of implants with different crown-to-root ratios. RESULTS AND CONCLUSION： We gained three-dimensional finite element models of mandible and mandibular dentition and mandibular prosthesis models of different crown-to-root ratios. When parallel to the direction of the implant was forced, the implant apical and around bone tissue were concentration zone of stress. The influences of different crown-to-root ratios are faint for jaw force in the direction of implant embedded, but great in the buccolingual direction. Therefore, the stability of the dental implant is considered in the horizontal direction. If space conditions are not permitted, the posterior area could be considered after a dental implant support.