Abstract:

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 indirectbleaching. Results The bleaching treatments had large impact on the crack growth resistance of human dentin. The initiation toughness（1.48 MPa·姨m）, growth toughness（3.90 MPa·姨m·mm-）1 and plateau toughness（3.25 MPa·姨m） of human dentin were reduced to 1.29 MPa·姨m , 3.45 MPa·姨m·mm-1 and 2.71 MPa·姨m respectively after indirectbleaching. The worst case was the direct -bleaching which causes significant reductions in the growth toughness
（0.14 MPa·姨m·mm-1）and plateau toughness（1.63 MPa·姨m）respectively, while the initiation toughness remained the same as that after indirect-bleaching. Conclusion The cohesive zone modeling is an effective tool in characterizing the fracture behavior of human dentin. Bleaching treatments reduce the crack growth resistance of human dentin and increase the risk of fracture of teeth.