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Wear and Mechanical Properties of Nano-silica-fused Whisker Composites

Paffenbarger Research Center, American Dental Association Foundation, National Institute of Standards and Technology, Building 224, Room A-153, Stop 8546, Gaithersburg, MD 20899-8546, USA;

View larger version (46K): [in this window] [in a new window]   Figure 1. Nano-silica-fused whisker, fracture toughness, and a notch. In (A), the nano-silica particles (S) are indicated by the arrow, and ‘W’ designates the whisker. In (B), each value is the mean of 6 measurements, with the error bar showing 1 standard deviation (SD) (mean ± SD; n = 6). Dissimilar letters indicate values that are significantly different (Tukey’s multiple-comparison test; family confidence coefficient = 0.95). In (C), optical micrograph shows an example of a notch in unfilled resin showing the sharpness of the notch tip produced by the single-edge-V-notched beam method.

View larger version (18K): [in this window] [in a new window]   Figure 2. Composite wear rates vs. nano-silica-fused whisker filler level. (A) Wear scar depth WD, (B) wear scar diameter WL, and (C) wear scar volume WV. Data for the prosthetic and inlay/onlay composite controls were included in each plot near the right axis. Each value is the mean of 6 measurements, with the error bar showing 1 standard deviation (mean ± SD; n = 6). The line through the data for the whisker composites was the linear best fit with the equation and the correlation coefficient R shown in each plot.

View larger version (162K): [in this window] [in a new window]   Figure 3. Worn surfaces. SEM micrographs inside wear scars after 400,000 cycles for (A) unfilled resin (0 %), and (B) and (C) whisker composites at filler levels of 60% and 74%, respectively. Arrows in (A) point to microcracks in the worn surface of the unfilled resin. The whisker composites in (B) and (C) had relatively smooth surfaces inside the wear scars, free of cracks like those in the unfilled resin. A higher magnification in (D) for whisker composite at the 70% filler level shows a worn-down whisker with the tip exhibiting signs of wear by microfracture (lower arrows). The left arrow in (D) indicates that the whisker was firmly embedded in the resin matrix.

View larger version (24K): [in this window] [in a new window]   Figure 4. Relationships between wear and mechanical properties. To understand the mechanisms of three-body wear of dental composites, we established linear best-fits between wear depth WD and (A) hardness H, (B) elastic modulus E, (C) flexural strength S, and (D) fracture toughness KIC of the nano-silica-fused whisker composites at filler level mass fractions ranging from 0% to 74%. Each value is the mean of 6 measurements, with the error bar showing 1 standard deviation (mean ± SD; n = 6).

Journal of Dental Research, Vol. 83, No. 12, 930-935 (2004)
DOI: 10.1177/154405910408301208


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