目的 研究漂白处理对牙本质力学性能的影响.方法 采用断裂力学中的内聚力模型并运用有限元分析法,分别模拟牙本质在未漂白、内漂白和外漂白3种状态下的裂纹扩展行为,研究漂白处理对牙本质抗折裂力学行为的影响.结果 漂白处理及方式对于牙本质的裂纹扩展阻力都有很大影响,经外漂白处理后的牙本质初始断裂韧度(1.29 MPa·√m)、扩展断裂韧度(3.45 MPa·√m·mm-1)和断裂韧度趋于恒定时的值(2.71 MPa·√m)都比未漂白牙本质的相应值(1.48 MPa·√m、3.90 MPa·√m ·mm-1、3.25 MPa·√m)小,而内漂白处理后的牙本质扩展断裂韧度(0.14 MPa·√m·mm-1)和断裂韧度趋于恒定时的值(1.63 MP·√m)都明显小于外漂白后牙本质的相应值,但是这两种漂白处理后的牙本质初始断裂韧度没有明显差别.结论 内聚力模型能很好地预测牙本质的断裂力学行为；漂白处理可以明显降低牙本质的断裂韧度,增加牙齿折裂的风险.%Objective To study the effect of bleaching on the mechanical properties of human dentin. Methods The finite element method (FEM) based the cohesive zone model had been employed to study the fracture resistance of human dentin. There types of dentin were considered, i.e. original dentin, dentin after direct-bleaching and indirect-bleaching. ResultsThe bleaching treatments had large impact on the crack growth resistance of human dentin. Therninitiation toughness (1.48 MPa·√m), growth toughness (3.90 MPa·√m·mm-1) and plateau toughness (3.25 MPa· √m ) of human dentin were reduced to 1.29MPa·√m, 3.45 MPa·√m·mm-1 and 2.71MPa·√m respectively after indirect-bleaching. The worst case was the direct-bleaching which causes significant reductions in the growth toughnessrn(0.14 MPa·√m 'mm-1) and plateau toughness (1.63 MPa·√m) respectively, while the initiation toughness remained the same as that after indirect-bleaching. ConclusionThe cohesive zone modeling is an effective tool in characteri-zing the fracture behavior of human dentin. Bleaching treatments reduce the crack growth resistance of human dentin and increase the risk of fracture of teeth.
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