IADR Abstract Archives

Dentino-enamel junction toughening mechanisms

The dentino-enamel junction (DEJ) durably unites dissimilar hard brittle enamel and tough flexible dentin. Unlike artificial junctions between restorations and dentin, the DEJ rarely fails except when it is affected by inherited disorders. Knowledge of DEJ toughening mechanisms is important in understanding inherited disorders, biomimetic engineering of artificial restorations, and in tissue engineering a DEJ. Objectives: To identify specific toughening mechanisms and measure fracture toughness across the human DEJ zone. Methods: Vickers indentations were made at 4 sites on each tooth, directly on the optical DEJ, approximately 35 um to the dentin side of the optical DEJ, approximately 35 um to the enamel side of the DEJ, and in distant bulk enamel. Interfacial fracture toughness was calculated in the customary way. Ten teeth were examined, with 5 repetitions made for each of the 4 test sites. Results: The DEJ zone did not function as a weak mechanical interface. The fracture toughness recorded by indentation at the optical DEJ (0.8 MPa.m1/2) was similar to that recorded by cracks driven by indentations located on the enamel and dentin sides of the DEJ, and to that of distant bulk enamel (p=0.08). Although some delamination occurred at the optical DEJ interface, damage was spread over a wide area and distinct toughening mechanisms discerned. The primary toughening mechanism involved the specialized "aprismatic" enamel close to the optical DEJ interface. Multiple, somewhat convoluted and sometimes branching, cracks spread and diffused damage over a wide area of adjacent enamel, preventing catastrophic interfacial failure. A second toughening mechanism involved short micro-cracks in the DEJ adjacent dentin with possible crack bridging. A third toughening mechanism involved plastic deformation of the DEJ without delamination. Conclusion: Specific toughening mechanisms combined to control, diffuse, and spread damage over the DEJ zone rather than permitting catastrophic interfacial failure. NIH/NIDCR DE12420 DE13045
IADR/AADR/CADR General Session
2002 IADR/AADR/CADR General Session (San Diego, California)
San Diego, California
2002
3186
Mineralized Tissue
  • White, Shane N  ( UCLA, Los Angeles, CA, USA )
  • Chang, Pei P  ( UCLA, Los Angeles, CA, USA )
  • Caputo, Angelo A  ( UCLA, Los Angeles, CA, USA )
  • Fong, Hanson  ( University of Washington, Seattle, WV, USA )
  • Sarikaya, Mehmet  ( University of Washington, Seattle, WV, USA )
  • Luo, Wen  ( University of Southern California, Los Angeles, CA, USA )
  • Paine, Michael L  ( University of Southern California, Los Angeles, CA, USA )
  • Snead, Malcolm L  ( University of Southern California, Los Angeles, CA, USA )
    • Oral Session
    Mineralization Structure/function
    03/09/2002