Within the limitations of this study, fabrication method, whether CAD/CAM or heat-pressed, had no effect on the marginal and internal adaptation of porcelain laminate veneers. The results showed that both fabrication techniques performed well after 2 years of clinical performance.
Solid oxide fuel cell (SOFC) electrode materials with surface areas up to 99 m 2 • g −1 were prepared at traditional sintering temperatures, 1050 • C-1350 • C, by sintering hybrid inorganic-organic materials in an inert atmosphere followed by calcination in air at 700 • C. The electrode materials investigated were yttria-stabilized zirconia (YSZ), lanthanum strontium cobalt ferrite (LSCF), gadolinia doped ceria (GDC), and strontium titanate (STO). During sintering, an amorphous carbon template forms in situ and remains throughout the sintering process, aiding in the creation and preservation of mixed-metal-oxide nanomorphology. The carbon template is removed during subsequent calcination in air at 700 • C, leaving behind a nanostructured ceramic. Phase stability, carbon template concentration, and specific surface area was determined for each mixed-metal-oxide. Final specific surface areas up to 83, 66, 95, and 99 m 2 • g −1 were achieved for YSZ, LSCF, GDC, and STO, respectively. The impact of high surface area YSZ on symmetrical YSZ-lanthanum strontium ferrite (LSF) cathode cell performance was evaluated in the temperature range of 550 • C-800 • C. Adding nanostructured YSZ decreased the electrochemical impedance by 45% at 550 • C. The performance improvement lessened with increasing temperature, and at 800 • C there was essentially no improvement. The findings reveal a promising approach to improving low temperature SOFC performance.
PURPOSETo determine whether the fracture strengths and failure types differed between metal and zirconia frameworks veneered with pressable or layering ceramics.MATERIALS AND METHODSA phantom molar tooth was prepared and duplicated in 40 cobalt-chromium abutments. Twenty metal (IPS d.SIGN 15, Ivoclar, Vivadent, Schaan, Liechtenstein) and 20 zirconia (IPS e.max ZirCAD, Ivoclar) frameworks were fabricated on the abutments. Each framework group was randomly divided into 2 subgroups according to the veneering material: pressable and layering ceramics (n=10). Forty molar crowns were fabricated, cemented onto the corresponding abutments and then thermocycled (5-55℃, 10,000 cycles). A load was applied in a universal testing machine until a fracture occurred on the crowns. In addition, failure types were examined using a stereomicroscope. Fracture load data were analyzed using one-way ANOVA and Tukey HSD post-hoc tests at a significance level of 0.05.RESULTSThe highest strength value was seen in metal-pressable (MP) group, whereas zirconia-pressable (ZP) group exhibited the lowest one. Moreover, group MP showed significantly higher fracture loads than group ZP (P=.015) and zirconia-layering (ZL) (P=.038) group. No significant difference in fracture strength was detected between groups MP and ML, and groups ZP and ZL (P>.05). Predominant fracture types were cohesive for metal groups and adhesive for zirconia groups.CONCLUSIONFracture strength of a restoration with a metal or a zirconia framework was independent of the veneering techniques. However, the pressing technique over metal frameworks resisted significantly higher fracture loads than zirconia frameworks.
The thermochemical stability of nanoscale yttria-stabilized-zirconia (nYSZ), processed via in situ carbon templating, was studied between 850 • C-1350 • C in four sintering atmospheres: Ar, N 2 , H 2 , and humidified H 2 . The in situ carbon templating method generates nanoscale ceramic particles surrounded by an amorphous carbon template upon sintering. The carbon template is subsequently removed by low temperature oxidation, leaving behind nanoscale ceramic particles. In Ar and H 2 , a ZrC impurity formed at temperatures ≥1150 • C. In humidified H 2 , either a ZrC impurity formed or the carbon template oxidized. In N 2 , ZrC was not observed over the temperature range studied and the carbon template was preserved. After carbon template removal, the nYSZ surface areas were high for Ar, H 2 , and N 2 : 55-99 m 2 • g −1 . For humidified H 2 , nYSZ surface area decreased as the carbon template was lost. Finally, nYSZ, processed in N 2 at 850 • C and 1250 • C, was integrated into symmetric YSZ-Lanthanum Strontium Ferrite (YSZ-LSF) cathode cells. The addition of nYSZ decreased cathode non-ohmic resistance, at 550 • C in air, by 40% and 27% for nYSZ processed at 850 • C and 1250 • C, respectively. This work demonstrates that N 2 is a thermochemically stable atmosphere for in situ carbon templating and that the resulting nYSZ considerably improves electrode performance.
Objectives:The objective of this study was to compare the accuracy of three different impression materials with evaluating the marginal fits of metal frameworks using replica technique. Materials and Methods:A phantom premolar tooth was prepared with a 1 mm circumferential chamfer preparation. Four impression materials: two vinyl polysiloxane (VPS) (Affinis Precious, (Group A); Elite HD, (Group E)), one polyether (Impregum Penta Soft, (Group P)) and one vinyl siloxanether (Identium, (Group I)) were used for producing stone casts of this master model. Twelve measurements per replica were carried out using a light microscope X40 magnification by Leica software, to assess the vertical marginal gap (VMG). Data were analyzed using the analysis of variance followed by Tukey's test (p=0.05).Results: Specimens of the Group A and Group I showed significantly lower VMG values than those of Group E and Group P (p<0.001). Differences were not significant between Group A and Group I, and Group E and Group P either (p>0.05).Conclusions: All impression materials were clinically acceptable. As well as composition of the impression materials, size of filler particles and fluid mechanics of flow into very small spaces can be effective on accuracy of the materials.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.