Abstract: Objective: To compare the stress magnitude and distribution of residual dentin in mandibular first molar restored with endocrown or post-core crown using three-dimension finite element methods. Methods: The three-dimensional finite element models of mandibular first molar were established after scanning by CT. A complete tooth was set as the control group. After simulating root canal therapy, three experimental group models with three kinds of defects were set as the experimental group: defect of mesial and distal proximal surface (group A); defect of buccal and mesial proximal surface (group B); defect of buccal, mesial, and distal proximal surface (group C). Then, endocrowns and post-core crowns were used to restore the defects. A load of 200N, simulating intercuspal occlusion, was applied vertically to the occlusal surface, and a load of 200 N simulating lateral occlusion was applied to the occlusal surface with a 45°angle to the long axis of the tooth. Von Mises stresses and max principal stresses were calculated by Abaqus software. Results: The stress of tooth tissue restored by endocrown was higher than that of post-core crown even more than 1 times. The stress of endocrown was concentrated in the pulp floor, and that of the post-core crown was concentrated in the distal apical 1/3. Conclusion: Endocrown and post-core crown are both applicable for mandibular first molar with large area defect, however, the post-core crown has better protective effect for the tooth tissue.

Key words: Post-core crown, Endocrown, Fracture resistance, Finite element analysis, Biomechanical analysis