Mono or polycrystalline alumina-modified hybrid ceramics

Abstract

Objectives This study evaluated the effect of addition of alumina particles (polycrystalline or monocrystalline), with or without silica coating, on the optical and mechanical properties of a porcelain. Methods Groups tested were: Control (C), Polycrystalline alumina (PA), Polycrystalline alumina-silica (PAS), Monocrystalline alumina (MA), Monocrystalline alumina-silica (MAS). Polycrystalline alumina powder was synthesized using a polymeric precursor method; a commercially available monocrystalline alumina powder (sapphire) was acquired. Silica coating was obtained by immersing alumina powders in a tetraethylorthosilicate solution, followed by heat-treatment. Electrostatic stable suspension method was used to ensure homogenous dispersion of the alumina particles within the porcelain powder. The ceramic specimens were obtained by heat-pressing. Microstructure, translucency parameter, contrast ratio, opalescence index, porosity, biaxial flexural strength, roughness, and elastic constants were characterized. Results A better interaction between glass matrix and silica coated crystalline particles is suggested in some analyses, yet further investigation is needed to confirm it. The materials did not present significant differences in biaxial flexural strength, due to the presence of higher porosity in the groups with alumina addition. Elastic modulus was higher for MA and MAS groups. Also, these were the groups with optical qualities and roughness closer to control. The PA and PAS groups were considerably more opaque as well as rougher. Significance: Porcelains with addition of monocrystalline particles presented superior esthetic qualities compared to those with polycrystalline particles. In order to eliminate the porosity in the ceramic materials investigated herein, processing parameters need to be optimized as well as different glass frites should be tested.

Functionalized pink Al 2 O 3 :Mn pigments applied in prosthetic dentistry

“…Note that before preparation of the composite resins, the pigment powder was functionalized by means of a sol-gel silica coating method. Previously published results of elemental mapping by EDS/SEM show a thin film of Si atoms on the surface of the alumina particles, 36 so the silica layer is not expected to significantly affect particle size. In addition, its presence allows for effective and stable silanation, 34 which is required for a strong bond between resin matrix and filler particles, and avoids interfacial pores that would compromise not only the mechanical properties of the composite resins 18–20 but also their translucency.…”

“…2,3,35,36 In this study, 0.01 M or 0.02 M manganese nitrate and 1 M aluminum nitrate were dissolved in water. Manganese/aluminum citrate forms by stirring in 3 M citric acid anhydrous (Sigma-Aldrich) at 50°C for 1 hour.…”

“…TEOS was added to the suspension in the proportion of 5 mol% relative to the powder. 36 Vigorous magnetic stirring was maintained and the temperature increased to 60°C to evaporate the aqueous content. After drying, the particles were heat treated in an air atmosphere oven with a 5°C/minute heating rate up to 900°C dwell temperature for 2 hours.…”

Microstructural and mechanical analysis of two CAD-CAM lithium disilicate glass-reinforced ceramics

“…The following scanning parameters were used: filter Al 0.5 & Cu 0.038; source voltage 90 kV; source current 111A; image pixel size 10.0m; 81 slices; lower gray threshold 60; upper gray threshold 190. 13 The total porosity percentage was measured, and 3D images contrasting the dense mass of the ceramic and the void spaces of the pores were collected. The reconstructed 3D data sets were quantified using a CTAn automated image analysis system (Brunker, Kontich, Belgium).…”

“…The percentage of pores and the ceramic characterization can also be determined by micro-computed tomography (µCT), which allows analysis without destroying the specimens. 13 Moreover, the flexural strength test is important to evaluate the maximum force to fracture and the flexural modulus of dental ceramics, properties that can help characterize the load capacity of the material. 14 Additionally, the interaction of glass ceramics with resin cements, and their bonding capability to these cements, are important clinical parameters, modulated by the composition and susceptibility of these ceramics to surface treatment with hydrofluoric acid etching associated to silane coupling agents.…”