Flexural Strength of Glass-Infiltrated Zirconia/Alumina-Based Ceramics and Feldspathic Veneering Porcelains

Purpose: To compare the flexural strength of two glass-infiltrated high-strength ceramics and two veneering glass-ceramics.Materials and Methods: Four ceramic materials were tested: two glass-infiltrated high-strength ceramics used as framework in metal-free restorations [In-Ceram Zirconia IZ (Gr1) and In-Ceram Alumina IA (Gr2)], and two glass-ceramics used as veneering material in metal-free restorations [Vita VM7 (Gr3) and Vitadur-alpha (Gr4)]. Bar specimens (25 x 5 x 2 mm(3)) made from core ceramics, alumina, and zirconia/alumina composites were prepared and applied to a silicone mold, which rested on a base from a gypsum die material. The IZ and IA specimens were partially sintered in an In-Ceram furnace according to the firing cycle of each material, and then were infiltrated with a low-viscosity glass to yield bar specimens of high density and strength. The Vita VM7 and Vitadur-alpha specimens were made from veneering materials, by vibration of slurry porcelain powder and condensation into a two-part brass Teflon matrix (25 x 5 x 2 mm(3)). Excess water was removed with absorbent paper. The veneering ceramic specimens were then removed from the matrix and were fired as recommended by the manufacturer. Another ceramic application and sintering were performed to compensate the contraction of the feldspar ceramic. The bar specimens were then tested in a three-point bending test.Results: The core materials (Gr1: 436.1 +/- 54.8; Gr2: 419.4 +/- 83.8) presented significantly higher flexural strength (MPa) than the veneer ceramics (Gr3: 63.5 +/- 9.9; Gr4: 57.8 +/- 12.7).Conclusion: In-Ceram Alumina and Zirconia were similar statistically and more resistant than VM7 and Vitadur-alpha.

Y-TZP ceramic processing from coprecipitated powders: A comparative study with three commercial dental ceramics

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Surface degradation of glass ceramics after exposure to acidulated phosphate fluoride

Objective: This study evaluated the surface degradation effect of acidulated phosphate fluoride (APF) gel exposure on the glassy matrix ceramics as a function of time. Material and methods: Disc-shaped ceramic specimens (N = 120, 10/per ceramic material) were prepared in stainless steel molds (inner diameter: 5 mm, height: 2 mm) using 6 dental ceramics: 3 indicated for ceramic-fused-to-metal (Vita Omega 900, Carmen and Vita Titankeramik), 2 for all-ceramic (Vitadur Alpha and Finesse (R) Low Fusing) and 1 for both types of restorations (IPS d. SIGN). The specimens were wet ground finished, ultrasonically cleaned and auto-glazed. All specimens were subjected to calculation of percentage of mass loss, surface roughness analysis and topographical description by scanning electron microscopy (SEM) before (0 min) and after exposure to 1.23 % APF gel for 4 min and 60 min representing short-and long-term etching effect, respectively. The data were analyzed using two-way ANOVA with repeated measures and Tukey` s test (alpha=0.05). Results: Significant effect of the type of the ceramics (p=0.0000, p=0.0031) and exposure time (p=0.0000) was observed in both surface roughness and percentage of mass loss values, respectively. The interaction factor between both parameters was also significant for both parameters (p=0.0904, p=0.0258). Both 4 min (0.44 +/- 0.1-0.81 +/- 0.2 mu m) and 60 min (0.66 +/- 0.1 - 1.04 +/- 0.3 mu m) APF gel exposure created significantly more surface roughness for all groups when compared to the control groups (0.33 +/- 0.2-0.68 +/- 0.2 mu m) (p<0.05). There were no significant differences in percentage of mass loss between the ceramics at 4 min (p>0.05) but at 60 min exposure, IPS d. SIGN showed the highest percentage of mass loss (0.1151 +/- 0.11). The mean surface roughness for Vita Titankeramik (0.84 +/- 0.2 mu m) and Finesse (R) Low Fusing (0.74.+/- 0.2 mu m) was significantly higher than those of the other ceramics (0.59 +/- 0.1 mu m - 0.49 +/- 0.1 mu m) and Vita Titankeramik (p<0.05) regardless of the exposure time. A positive correlation was found between surface roughness and percentage of mass loss for all ceramic materials [(r=0.518 (Vitadur Alpha), r=0.405 (Vita Omega 900), r=0.580 (Carmen), r=0.687 (IPS d. SIGN), r=0.442 (Finesse (R) Low Fusing), r=0.572 (Vita Titankeramik), Pearson's correlation coefficient)]. The qualitative SEM analysis showed evidence of corrosive attack on all of ceramics at varying degrees. Conclusions: The ceramics indicated for either metal-ceramic or all-ceramic restorations were all vulnerable to surface texture changes and mass loss after short-term and long-term APF gel exposure.

Mechanical and thermal cycling effects on the flexural strength of glass ceramics fused to titanium

This study evaluated the effects of mechanical and thermal cycling on the flexural strength (ISO 9693) of three brands of ceramics fused to commercially pure titanium (cpTi). Metallic frameworks of 25 x 3 x 0.5 mm dimensions (N = 84) were cast in cpTi, followed by 150-mu m aluminum oxide airborne particle abrasion at a designated area of the frameworks (8 x 3 mm). Bonder and opaque ceramic were applied on the frameworks, and then the corresponding ceramic (Triceram, Super Porcelain Ti-22, Vita Titankeramik) was fired onto them (thickness: 1 mm). Half of the specimens from each ceramic-metal combination were randomly tested without aging (only water storage at 37 degrees C for 24 hours), while the other half were mechanically loaded (20,000 cycles under 10 N load, immersion in distilled water at 37 degrees C) and thermocycled (3,000 cycles, between 5-55 degrees C, dwell time of 13 seconds). After the flexural strength test, failure types were noted. Mechanical and thermal cycling decreased the mean flexural strength values significantly (p<0.05) for all the three ceramic-cpTi combinations tested when compared to the control group. In all the three groups, failure type was exclusively adhesive at the opaque ceramic-cpTi interfacial zone with no presence of ceramic on the substrate surface except for a visible oxide layer.

Relaxor behavior in multiferroic BiMn2O5 ceramics

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Síntese e caracterização da cerâmica PZT dopada com íons bário

Pós de titanato zirconato de chumbo (PZT) puros e dopados com bário foram obtidos pelo método de precursores poliméricos, conformados uniaxialmente, na forma de cilindros, utilizando 15 MPa, e prensados isostaticamente à 210MPa. Com o objetivo de estudar o comportamento de sinterização os compactos foram divididos em dois lotes. Sendo um sinterizado em um forno acoplado a um dilatômetro até a temperatura de 1300 °C e o outro sinterizado em forno tipo mufla, em sistema fechado, na temperatura de 1100 °C por 4 horas. Verificou-se que a adição do íon bário influencia na cinética de sinterização, na densificação final, na microestrutura e nas propriedades elétricas da cerâmica. A adição de bário aumenta a concentração da fase tetragonal no PZT, em função da substituição do chumbo por bário na rede perovskita. As amostras dopadas com concentrações maiores que 5,0 mol % em bário apresentaram segregação de PbO no contorno de grão, inibindo seu crescimento.

Nanosized lead lanthanum titanate (PLT) ceramic powders synthesized by the oxidant peroxo method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Study on the K3Li2Nb5O15 formation during the production of (Na0.5K0.5)((1-x))LixNbO3 lead-free piezoceramics at the morphotropic phase boundary

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis and characterization of lead zirconate titanate powders obtained by the oxidant peroxo method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A homovalent doping in PMN ceramics by using lithium and scandium cations

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Response of human alveolar bone-derived cells to a novel poly(vinylidene fluoride-trifluoroethylene)/barium titanate membrane

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Strain and vacancy cluster behavior of vanadium and tungsten-doped Ba[Zr(0.10)Ti(0.90)]O(3) ceramics

Strain and vacancy clusters behavior of polycrystalline vanadium (V) and tungsten (W)-doped Ba[Zr(0.10)Ti(0.90)]O(3), (BZT:2%V) and (BZT:2%W) ceramics obtained by the mixed oxide method was evaluated. Substitution of V and W reduces the distortion of octahedral clusters, decreasing the Raman modes. Electron paramagnetic resonance data indicate that the addition of dopants leads to defects and symmetry changes in the BZT lattice. Remnant polarization and coercive field are affected by V and W substitution due the electron-relaxation mode. The unipolar strain E curves as a function of electric field reach its maximum value for BZT:2%V and BZT:2%W ceramics. (c) 2008 American Institute of Physics.

Contribution of structural order-disorder to the room-temperature photoluminescence of lead zirconate titanate powders

Intense and broad visible photoluminescent (PL) band was observed at room temperature in structurally disordered PbZr0.53Ti0.47O3 powders. The lead zirconate titanate PbZr0.53Ti0.47O3 powders prepared by the polymeric precursor method and heat treated at different temperatures were structurally characterized at long range by means of X-ray diffraction. The PL was measured at room temperature samples heat treated at different temperatures. Experimental measurements and quantum-mechanical calculations showed that the high structural order and the high structural disorder in PbZr0.53Ti0.47O3 lattice are not favorable to the intense PL emission. Only samples containing simultaneous structural order and disorder in their lattice present the intense visible PL emission at room temperature. (C) 2007 Published by Elsevier B.V.

Barium strontium titanate powders prepared by spray pyrolysis

Ultasonic spray pyrolysis (SP) has been investigated for the production of the barium strontium titanate (BST) powders from the polymeric precursors. The processing parameters, such as flux of aerosol and temperature profile inside the furnace, were optimized to obtain single phase BST. The powders were characterized by the methods of X-ray diffraction analysis, SEM, EDS and TEM. The obtained powders were submicronic, consisting of spherical, polycrystalline particles, with internal nanocrystalline structure. Crystallite size of 10 nut, calculated using Rietveld refinement, is in a good agreement with results of HRTEM. (c) 2005 Elsevier B.V. All rights reserved.