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Lifetime-limiting Strength Degradation from Contact Fatigue in Dental CeramicsMaterials Science and Engineering Laboratory, Building 223, Room B309, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
Materials Science and Engineering Laboratory, Building 223, Room B309, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
Materials Science and Engineering Laboratory, Building 223, Room B309, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
Materials Science and Engineering Laboratory, Building 223, Room B309, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA The hypothesis under examination in this paper is that the lifetimes of dental restorations are limited by the accumulation of contact damage during oral function; and, moreover, that strengths of dental ceramics are significantly lower after multi-cycle loading than after single-cycle loading. Accordingly, indentation damage and associated strength degradation from multi-cycle contacts with spherical indenters in water are evaluated in four dental ceramics: "aesthetic" ceramics-porcelain and micaceous glass-ceramic (MGC), and "structural" ceramics—glass-infiltrated alumina and yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). At large numbers of contact cycles, all materials show an abrupt transition in damage mode, consisting of strongly enhanced damage inside the contact area and attendant initiation of radial cracks outside. This transition in damage mode is not observed in comparative static loading tests, attesting to a strong mechanical component in the fatigue mechanism. Radial cracks, once formed, lead to rapid degradation in strength properties, signaling the end of the useful lifetime of the material. Strength degradation from multi-cycle contacts is examined in the test materials, after indentation at loads from 200 to 3000 N up to 106 cycles. Degradation occurs in the porcelain and MGC after ~ 104 cycles at loads as low as 200 N; comparable degradation in the alumina and Y-TZP requires loads higher than 500 N, well above the clinically significant range.
Key Words: contact fatigue damage accumulation dental ceramics fracture strength degradation.
Journal of Dental Research, Vol. 79, No. 2,
722-731 (2000) This article has been cited by other articles:
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