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Degradation, Fatigue, and Failure of Resin Dental Composite Materials
J.L. Drummond
337A College of Dentistry, Department of Restorative Dentistry m/c 555, 801 South Paulina Street, University of Illinois at Chicago, Chicago, IL 60612-7212, USA; drummond{at}uic.edu
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Figure 1. SEM of typical filer particles showing a colloidal filler, OX 50, and 2 microfillers, Z100 and a Sr-SiO2 glass, showing the differences in size and shape.
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Figure 2. SEM of Renew, a microhybrid of, by weight. 28% resin and 72% glass filler particles, with an average particle size distribution of 5% 0.004 mm, 62% 0.7 mm and 5% 3–7 mm particles. The Fig. represents the fracture of specimens aged for 6 mos in 3 media: air, distilled water, and a 50/50 by volume mixture of ethanol and distilled water.
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Figure 3. SEM of Filtek, a nanofiller of, by weight, 78.5%, 25–75 nm filler particles and 21.5% resin. The Figs. show how the nanoparticles are formed as 5-mm clusters and are pulled out of the resin matrix during fracture. The specimens aged in the 50/50 mixture demonstrate degradation (weakening of mechanical properties) by a lack of sharpness in the fracture surface. The Figs. represent the fracture of specimens aged for 6 mos in 3 media: air, distilled water, and a 50/50 by volume mixture of ethanol and distilled water.
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Figure 4. SEM of Restolux, a fiber filler by weight 85% filler and 15% resin, with the filler composed of 3-to 4-mm particles (~ 27%) and 80- to 120-mm fibers (~ 52%). The SEMs indicate the relatively large size of the fiber filler compared with the surrounding particle filler, and the separation of the fiber filler from the resin matrix (c, f), compared with the other aging media. The separation is most likely a combination of aging in the 50/50 mixture and polymerization shrinkage stress release. The Figs. represent the fracture of specimens aged for 6 mos in 3 media: air, distilled water, and a 50/50 by volume mixture of ethanol and distilled water.
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Figure 5. SEM of fracture surfaces of specimens: (A) control A, (B) SiC whisker composite, and (C) Si3N4 whisker composite, all after one-day immersion. The fracture surfaces of the controls were relatively flat. In contrast, the whisker composites had much rougher surfaces, with fracture steps (large arrows) and whisker pull-out (small arrows) (Xu, 2003, reprinted with permission).
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Figure 6. SEM of whisker pull-out on fracture surfaces of Si3N4 composite: (A) 1 day, (B) 400 days, and (C) 730 days of water aging, with shorter whisker pull-out at 400 and 730 days. Polymer remnants were observed on the pulled-out whiskers (arrows), indicating good whisker-polymer matrix bonding, even after 730 days of water aging (Xu, 2003, reprinted with permission).
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Figure 7. Fracture toughness vs. number of cycles completed for Renew and Restolux with a Diametral (Brazilian) disc specimen of controls and aged specimens for 3 mos. Cyclic loading had little effect on the fracture toughness for the control specimens, but, in conjunction with aging, had a major effect for the aged specimens. Aging in the 50/50 mixture of ethanol and distilled water caused the greatest decrease in fracture toughness.
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Figure 8. Reconstructions (a-d) of the images taken at the Advanced Photon Source of a Renew specimen subjected to multi-axial compression at a strain level of 12%, demonstrating the crack pattern after loading. The 3D reconstruction of the same Renew specimen in (a-d), indicating the complexity and distribution of the cracking within the specimen with (e) looking down the axial axis and (f) off-axis.
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Journal of Dental Research, Vol. 87, No. 8,
710-719 (2008)
DOI: 10.1177/154405910808700802
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