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The dentin–enamel junction and the fracture of human teeth

Nature Materials volume 4, pages 229–232 (2005)Cite this article

Abstract

The dentin–enamel junction (DEJ), which is the interfacial region between the dentin and outer enamel coating in teeth, is known for its unique biomechanical properties that provide a crack-arrest barrier for flaws formed in the brittle enamel1. In this work, we re-examine how cracks propagate in the proximity of the DEJ, and specifically quantify, using interfacial fracture mechanics, the fracture toughness of the DEJ region. Careful observation of crack penetration through the interface and the new estimate of the DEJ toughness (∼5 to 10 times higher than enamel but ∼75% lower than dentin) shed new light on the mechanism of crack arrest. We conclude that the critical role of this region, in preventing cracks formed in enamel from traversing the interface and causing catastrophic tooth fractures, is not associated with the crack-arrest capabilities of the interface itself; rather, cracks tend to penetrate the (optical) DEJ and arrest when they enter the tougher mantle dentin adjacent to the interface due to the development of crack-tip shielding from uncracked-ligament bridging.

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Figure 1: Typical profiles of the Vickers hardness and the indentation toughness.
Figure 2: Optical micrograph of the placement of Vickers indents in the enamel.
Figure 3: The linear-elastic solutions of He and Hutchinson22.
Figure 4: SEM examples of arrested cracks.

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Acknowledgements

This work was supported in part by the National Institutes of Health, National Institute of Dental and Craniofacial Research, under Grant No. R01 DE 13029 (for V.I., G.W.M., S.J.M.), and by the Director, Office of Science, Office of Basic Energy Science, Division of Materials Sciences and Engineering of the Department of Energy under Contract No. DE-Ac03-76SF00098 (for J.J.K., R.O.R.). The authors wish to thank Grace Nonomura for specimen preparation, and Cynthia Chao, Kevin Liu, Earnst Young, Ravi Nalla and Eduardo Saiz for experimental assistance.

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  1. V. Imbeni

    Present address: SRI International, Menlo Park, California, 94025, USA

Authors and Affiliations

  1. Materials Sciences Division, and Department of Materials Science and Engineering, Lawrence Berkeley National Laboratory, University of California, Berkeley, 94720, California, USA

    V. Imbeni, J. J. Kruzic & R. O. Ritchie

  2. Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, 94143, California, USA

    G. W. Marshall & S. J. Marshall

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Correspondence to R. O. Ritchie.

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Imbeni, V., Kruzic, J., Marshall, G. et al. The dentin–enamel junction and the fracture of human teeth. Nature Mater 4, 229–232 (2005). https://doi.org/10.1038/nmat1323

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