Dental Materials
Volume 25, Issue 7 , Pages 909-916, July 2009

Mechanistic aspects of fatigue crack growth behavior in resin based dental restorative composites

  • M.B. Shah

      Affiliations

    • Materials Science, School of Mechanical, Industrial, and Manufacturing Engineering, Oregon State University, Corvallis, OR, USA
    • ,
  • J.L. Ferracane

      Affiliations

    • Division of Biomaterials & Biomechanics, School of Dentistry, Oregon Health & Science University, Portland, OR, USA
    • ,
  • J.J. Kruzic

      Affiliations

    • Materials Science, School of Mechanical, Industrial, and Manufacturing Engineering, Oregon State University, Corvallis, OR, USA
    • Corresponding Author InformationCorresponding author at: Oregon State University, 204 Rogers Hall, Corvallis, OR 97331, USA. Tel.: +1 541 737 7027; fax: +1 541 737 2600.

Received 17 November 2008; received in revised form 15 January 2009; accepted 19 January 2009.

Abstract 

Objective

To test the hypothesis that a commercial microhybrid resin based composite (Filtek™ Z250) has superior fatigue resistance to a nanofill composite (Filtek™ Supreme Plus) and to determine the related micromechanisms involved in the fatigue process.

Methods

After 60 days of water hydration, the fatigue crack growth resistance of two different resin composites, one microhybrid (Filtek™ Z250) and one nanofill (Filtek™ Supreme Plus), was measured in wet conditions using compact-tension, C(T), specimens at a load ratio of 0.1 and frequency of 2Hz. Cyclic fatigue behavior was quantified in terms of the fatigue crack growth rate, da/dN, as a function of the stress intensity range, ΔK.

Results

A sigmoidal da/dN-ΔK curve with three different fatigue crack growth regimes was identified for both composites. In general, fatigue crack growth ranged from ∼10−9 to 10−5m/cycle over ΔK of 0.54–0.63MPa√m for the Z250 composite and ΔK of 0.41–0.67MPa√m for the Supreme Plus composite. The Supreme Plus composite showed a lower fatigue threshold, ΔKth, by ∼0.13MPa√m compared to the Z250 composite, while also showing a plateau in the fatigue crack growth curve that is likely related to environmental attack. SEM observations of the fatigue crack paths and fracture surfaces revealed an interparticle crack path and extrinsic toughening mechanisms of crack deflection and crack bridging. No fatigue degradation of reinforcing particles or clusters was found, but cluster–matrix debonding was evident in the Supreme Plus composite, also indicative of environmental attack due to water.

Significance

This study increases the understanding of both the fatigue behavior and the micromechanisms of fatigue in resin based dental composites.

Keywords: Resin composite, Fatigue, Crack growth, Crack bridging, Hydration

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PII: S0109-5641(09)00110-9

doi:10.1016/j.dental.2009.01.097

Dental Materials
Volume 25, Issue 7 , Pages 909-916, July 2009

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