133 research outputs found
Fluid flow after resin-composite restoration in extracted carious teeth
The aim of this study was to investigate fluid flow in dentin after restoration of carious teeth with resin composite bonded with a total-etching adhesive, with or without glass-ionomer cement lining. The roots of extracted third molars were removed and the crowns were connected to a fluid flow-measuring device. Each carious lesion was stained with caries detector dye and caries was removed using slow-speed burs and spoon excavators. Caries-excavated teeth were divided into two groups for restoration with resin composite bonded with a total-etch adhesive: (i) without lining; and (ii) lined with glass-ionomer cement before bonding. In non-carious teeth, cavities of similar dimensions were prepared, divided into two groups, and restored in the same manner. Fluid flow was recorded, after restoration, for up to 1 month. Caries-affected dentin was examined by scanning electron microscopy (SEM), and the bonded interfaces were observed using a confocal laser scanning microscope. No significant difference in fluid flow was observed between the two restorative procedures or between the carious and non-carious groups. The SEM images showed that the dentinal tubules of acid-etched, caries-affected dentin were usually still occluded, while some were patent. Limited penetration of fluorescent dye into dentin and into the bonded interfaces of restored carious teeth was observed. © 2009 Eur J Oral Sci.link_to_subscribed_fulltex
Densification, Microstructure, and Mechanical Properties of ZrC-SiC Ceramics
ZrC-SiC ceramics were fabricated by high-energy ball milling and reactive hot pressing of ZrH2, carbon black, and varying amounts of SiC. The ceramics were composed of nominally pure ZrC containing 0 to 30 vol% SiC particles. The relative density increased as SiC content increased, from 96.8% for nominally pure ZrC to 99.3% for ZrC-30 vol% SiC. As SiC content increased from 0 to 30 vol%, Young\u27s modulus increased from 404 ± 11 to 420 ± 9 GPa and Vickers hardness increased from 18.5 ± 0.7 to 23.0 ± 0.5 GPa due to a combination of the higher relative density of ceramics with higher SiC content and the higher Young\u27s modulus and hardness of SiC compared to ZrC. Flexure strength was 308 ± 11 MPa for pure ZrC, but increased to 576 ± 49 MPa for a SiC content of 30 vol%. Fracture toughness was 2.3 ± 0.2 MPa·m1/2 for pure ZrC and increased to about 3.0 ± 0.1 MPa·m1/2 for compositions containing SiC additions. The combination of high-energy ball milling and reactive hot pressing was able to produce ZrC-SiC ceramics with sub-micron grain sizes and high relative densities with higher strengths than previously reported for similar materials
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