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Contact Damage Resistance and Strength Degradation of Glass-infiltrated Alumina and Spinel Ceramics

Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899

I.M. Peterson

Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899

A. Pajares

Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899

B.R. Lawn

Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899

All-ceramic crowns are coming into widespread use because of their superior esthetics and chemical inertness. This study examines the hypothesis that glass-infiltrated alumina and spinel core ceramics are resistant to damage accumulation and strength degradation under representative oral contact conditions. Accordingly, Hertzian indentation testing with hard spheres is used to evaluate damage accumulation in alumina and spinel ceramics with different pre-form grain morphologies and porosities. Indentation stress-strain curves measured on fully infiltrated materials reveal a marked insensitivity to the starting pre-form state. The glass phase is shown to play a vital role in providing mechanical rigidity and strength to the ceramic structures. All the infiltrated ceramics show subsurface cone fracture and quasi-plastic deformation above critical loads Pc (cracking) and Py (yield), depending on sphere radius, with Py < Pc. Strength degradation from accumulation of damage in Hertzian contacts above these critical loads is conspicuously small, suggesting that the infiltrated materials should be highly damage-tolerant to the "blunt" contacts encountered during mastication. Failure in the strength tests originates from either cone cracks ("brittle mode") or yield zones ("quasi-plastic mode"), with the brittle mode more dominant in the spinels and the quasi-plastic mode more dominant in the aluminas. Multi-cycle contacts at lower loads, but still above loads typical of oral function, are found to be innocuous up to 105 cycles in air and water, although contacts at 106 cycles in water do cause significant strength degradation. By contrast, contacts with Vickers indenters produce substantial strength losses at low loads, suggesting that the mechanical integrity of these materials may be compromised by inadvertent "sharp" contacts.

Key Words: alumina • cracking • deformation • dental ceramics • Hertzian contact • microstructure • spinel • strength

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Journal of Dental Research, Vol. 78, No. 3, 804-814 (1999)
DOI: 10.1177/00220345990780031401


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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Jung, Y.-G. Articles by Lawn, B.R. Search for Related Content PubMed PubMed Citation Articles by Jung, Y.-G. Articles by Lawn, B.R. Social Bookmarking                         What's this?