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[The effect of bleaching on fracture resistance in human dentin]
Yuanzhi Xu1, Raorao Wang, Bingbing An
1Dept. of Stomatology, The Tenth People's Hospital Affiliated to Tongji University, Shanghai 200072, China.
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.
Results:
The bleaching treatments had large impact on the crack growth resistance of human dentin. The initiation toughness (1.48 MPa x square root of m), growth toughness (3.90 MPa x square root of m x mm(-1)) and plateau toughness (3.25 MPa x square root of m) of human dentin were reduced to 1.29 MPa x square root of m, 3.45 MPa x square root of m x mm(-1) and 2.71 MPa x square root of m respectively after indirect-bleaching. The worst case was the direct-bleaching which causes significant reductions in the growth toughness (0.14 MPa x square root of m x mm(-1)) and plateau toughness (1.63 MPa x square root of 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.
