关键词: 桩核, 弹性模量, 有限元分析, 计算机辅助设计与制造, 最大应力值, 等效应力

Abstract: BACKGROUND: Post and core restoration is a common choice for tooth defects, but the repair effects of various post and core materials are different.
Objective: To evaluate the stress distribution at the post and core, tooth root, and bonding agent site of post and core models made of different elastic modulus post and core materials using finite element method. 
Methods: A three-dimensional root canal treated maxillary central incisor model was built using three-dimensional modeling software, which was restored with a full ceramic crown. The post and core materials in the restoration used nanoceramic resin (elastic modulus=12.8 GPa), composite resin (elastic modulus=16 GPa), hybrid ceramic (elastic modulus=34.7 GPa), glass ceramic (elastic modulus=95 GPa), titanium alloy (elastic modulus=112 GPa), and zirconia (elastic modulus=209.3 GPa). The model was fixed in cortical bone. A 100 N concentrated force of 45° from the long axis of the tooth was applied to 1/3 of the crown and tongue side of the central incisor. The stress distribution of the post and core, dentin, and tooth-root bonding agent in the model was repaired by the maximum principal stress criterion.
Results and conclusion: (1) When the post and core materials with higher elastic modulus was used, the post-core stress in the repair model was more concentrated. When the elastic modulus of the post and core materials (nanoceramic resin and composite resin) was close to dentin, the stress distribution of the post and core was more uniform. The stress distribution of dentin in all restoration models was similar regardless of post and core materials. When the post and core with higher elastic modulus was used, more stress concentration was shown at the post and root bonding agent in the repair model. (2) The maximum stress values at the post and core, tooth root, and the bonding agent site of post and tooth root in the nanoceramic resin model were 31.00, 33.21, and 0.51 MPa, respectively. The maximum stress values at the post and core, tooth root, and the bonding agent between the post and tooth root in the composite resin model were 36.84, 33.14, and 0.59 MPa, respectively. In the mixed ceramic model, the maximum stress values at the post and core, tooth root, and the bonding agent between the post and tooth root were 64.05, 32.83, and 1.00 MPa, respectively. In the glass ceramic model, the maximum stress values at the post and core, tooth root, and the bonding agent between the post and tooth root were 112.30, 32.69, and 1.73 MPa, respectively. In the titanium alloy model, the maximum stress values of the post and core, tooth root, and the bonding agent between the post and tooth root were 120.00, 32.17, and 1.86 MPa, respectively. In the zirconia model, the maximum stress values of the post and core, tooth root, and the bonding agent between the post and tooth root were 148.80, 31.85, and 2.28 MPa, respectively. (3) The higher the elastic modulus of the post and core material, the higher the maximum stress at the post and core during restoration. The elastic modulus of the post and core material had no significant effect on the maximum stress of the dental bonding agent and dentin.

Key words: post and core, elastic modulus, finite element analysis, computer aided design/computer aided manufacture, maximum stress value, equivalent stress