Abstract: Abstract: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 mm,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.

Key words: split post-crown, split , post-core-crown, finite element analysis