三维有限元法分析分裂桩冠与分裂桩核冠修复下颌第一磨牙残根的应力分布特点

3-Dimensinal finite element analysis on characteristics of stress distribution of residual root of first mandibular molar repaired by split post crown and split post-core crown

目的:通过三维有限元法对比分析分裂桩冠和分裂桩核冠2种桩核系统修复下颌第一磨牙低牙合龈距离残根的应力分布特点,为其临床应用提供客观参数。方法:选取离体下颌第一磨牙,获取其残根及修复体的CT影像。借助逆向工程软件MIMICS及模型修复软件MAGICS,通过CT影像建立起分裂桩冠及分裂桩核冠2种修复方案的有限元模型。装配好的模型在大型通用有限元软件ABAQUS中设置材料属性、接触关系、约束、载荷等信息后进行应力分析。结果:应力分析结果,垂直载荷下,分裂桩冠根管内部及根管口处所受应力明显高于分裂桩核冠(P<0.05);侧向载荷下,分裂桩冠根管内部及根管口处所受应力也明显高于分裂桩核冠(P<0.05)。外冠位移分析结果,在垂直载荷过程中,2种修复系统牙冠的最大位移均约为0.01mm,组间比较差异无统计学意义(P>0.05);在侧向载荷过程中,分裂桩核冠牙冠的最大位移明显大于分裂桩冠,差异有统计学意义(P<0.05)。结论:在选用分裂桩冠修复时,应采用多种措施加强根管口处根管壁的抗力性能,加强根管口处的抗力性,降低残根所受牙合力,从而保证最终的修复效果。

Objective To compare the stress distribution of the residual root of first mandibular molar between the split post-crown rehabilitation system and split post-core-crown rehabilitation system with 3-dimensional finite element, and to offer proper parameters for clinical application. Methods An excised first mandibular molar was chosen to get a CT scanning in the area of its residual root. By reverse engineering software MIMICS and model reconstructing software MAGICS, the 3-dimensional model of such rehabilitation systems were built. The features of a model, such as material properties, contact reactions, restrains, and loads were set under the software of ABAQUS. Results The stress analysis results showed that under vertical loads, the post-crown rehabilitation system appeared a stronger stress concentration at the contact position between the post and the root canal than the post-core-crown rehabilitation system （P〈0.05）; meanwhile, under lateral loads, a significant stronger stress concentration appeared in the post-crown rehabilitation system of the point between the crown and the post compared with the post-core-crown rehabilitation system （P〈0.05）. On the same position of a model, the force on root canal caused by lateral loads was greater than that of vertical loads. Under the same amount of loads, the root canal orifice suffered a greater force than internal part of the root canal, and there was significant difference （P^0.05）. The offset analysis results of the crown indicated that under vertical loads, the maximum displacements of the two systems were both 0.01 ram, and there was no significant difference （P〉0.05）. While under lateral loads, the post-core-crown had a greater maximum displacement than the post-crown, and there was significant difference （P〈0.05）. Conclusion When applying the split post-crown rehabilitation system, several measures should be take to enhance the resistance performance of the root canal orifice and reduce the force that residual roots suffer in order to get the prosthodontic treatment better.