Flexural strength of a glass-infiltrated alumina dental ceramic incorporated with silicon carbide whiskers.

PURPOSE: The addition of silicon carbide whiskers has been known to reinforce ceramics. This study compared the flexural strength of a glass-infiltrated alumina dental ceramic with various amounts of silicon carbide whiskers incorporated into the alumina matrix. MATERIALS AND METHODS: Three groups with a total of 30 specimens were included: glass-infiltrated alumina dental ceramic with 0, 0.125, and 0.25 wt% silicon carbide whiskers. The flexural strength was measured using a three-point bending test, and the data were analyzed with one-way analysis of variance. Scanning electron microscopy was used to examine the fracture surfaces of all three materials. RESULTS: There were no significant differences in the flexural strength among the three groups. Glass-infiltrated alumina dental ceramic failed predominantly by transgranular fracture and to a lesser degree by intergranular fracture. CONCLUSION: The addition of silicon carbide whiskers did not change the flexural strength of glass-infiltrated alumina dental ceramic.

Comparative mechanical property characterization of 3 all-ceramic core materials.

PURPOSE: The biaxial flexural strength and fracture toughness for 3 representative types of ceramic core materials were studied to (1) ascertain the ranking of the 3 ceramic types for strength and toughness, and (2) provide clinicians with more information to predict clinical outcomes. The former aim was deemed important in view of the importance of flaw size in the relationship between failure stress and fracture toughness of brittle materials. MATERIALS AND METHODS: The 3 representative ceramic types included a leucite-reinforced glass, a glass-infiltrated sintered alumina, and a high-purity, high-density alumina. The biaxial flexural strength was measured with the piston-on-3-ball method. The plane-strain fracture toughness was measured with the short-bar chevron-notch method. RESULTS: The biaxial flexural strengths of the high-purity, high-density alumina and glass-infiltrated sintered alumina ceramic core types were significantly higher than that of the leucite-reinforced glass ceramic type. The glass-infiltrated sintered alumina was significantly higher in fracture toughness than the high-purity, high-density alumina type, which was significantly higher than the leucite-reinforced glass. CONCLUSION: All materials surpassed the minimum strength requirement outlined by the International Standards Organization, and they also had similar strength variability according to their Weibull moduli. The glass-infiltrated sintered alumina and the high-purity, high-density alumina types were significantly stronger and tougher than currently used core materials. However, while the glass-infiltrated sintered alumina had a higher fracture toughness than the high-purity, high-density alumina, it had a lower flexural strength.

A comparison of the marginal fit of In-Ceram, IPS Empress, and Procera crowns.

The in vitro marginal fit of three all-ceramic crown systems (In-Ceram, Procera, and IPS Empress) was compared. All crown systems were significantly different from each other at P = 0.05. In-Ceram exhibited the greatest marginal discrepancy (161 microns), followed by Procera (83 microns), and IPS Empress (63 microns). There were no significant differences among the various stages of the crown fabrication: core fabrication, porcelain veneering, and glazing. The facial and lingual margins exhibited significantly larger marginal discrepancies than the mesial and distal margins.

Use of the Munsell system to compute color differences in composite resins.

Color changes resulting from immersion of four composite resins in hot distilled water, coffee and tea were measured by a tristimulus colorimeter. Changes are shown as CIE deltaE values and converted to Munsell deltaH, deltaV and deltaC values.