Jie Mo Tian

The Color of Fe2O3 and Bi2O3 Pigmented Dental Zirconia Ceramic

The aim of this study was to explored the effects of Fe2O3 and Bi2O3 on the color properties of a 3Y-TZP zirconia ceramics for dental application. Pigmented dental ZrO2 powders were prepared by mixing different concentration of Fe2O3 and Bi2O3, also in their combinations with 3Y-TZP powders. The mixture was compacted by isostastic pressure, then densely sintered. Color parameters were measured by Minolta CM2600d spectrophotometer. XRD was used to exam the structure of colored 3Y-TZP. Experimental results showed that the hue of the materials shift from yellow-green to yellow-red with the increasing concentration of the Fe2O3 and Bi2O3. Combined use of Fe2O3 and Bi2O3 could further decrease the L* value, which color scope was suitable for dental color matching. The XRD spectra showed only tetragonal phase was detected.

Strength and Fracture Mode for Dental Colored ZrO2 Ceramics Coated with Dental Porcelain

The purpose of this study was to investigate the flexural strength and the mode of failure of dental colored ZrO2 ceramics with or without porcelain coating. Colorants (Fe2O3,CeO2, etc.) were mixed with 3Y-TZP powder to prepare colored dental zirconia. Specimens were made in monolithic or bilayered forms which were coated with veneering porcelain. Experimental results showed that there were not significantly differences of bending strengths between white and colored materials or between bilayered specimen, while the strength of monolithic specimen were significantly higher than their bilayered counterpart. In all bilayered specimens, the bulk fracture initiated at the tensile surface of the core material and was consistently accompanied with porcelain crush and delamination at the interface. Colorants for 3Y-TZP had minor effects on its mechanical properties.

Preparation and Characterization of Biodegradable β-TCP-Based Composite Microspheres as Bone Tissue Engineering Scaffolds

Since a small globular particle was first used as support for three-dimensional (3D) growth of anchorage-dependent cells in suspended cultures, a variety of microspheres as tissue engineering scaffolds have been developed. In this paper, β-TCP and chitosan were selected as the components of microspheres due to their biodegradability and osteogenic properties. The biodegradable β-TCP/chitosan composite microspheres were prepared by a solid-in-water-in-oil (s/w/o) emulsion cross-linking method in this paper. The size distribution, surface morphology, and microstructure of the microspheres were evaluated. Scanning electron microscopy revealed that the size of the microspheres with good spherical morphology was distributed in the range of 50~200μm. In vitro immersion experiments were carried out to evaluate the degradability of the microspheres, and the results demonstrated that the chitosan/β-TCP composite microspheres were potential materials as tissue engineering scaffolds for bone repair.

One-Step Approach for the Fabrication and Characterization of Hydroxyapatite/TiO2 Composite Ceramic Coatings by Micro-Arc Oxidation In Situ on the Surface of Pure Titanium

The hydroxyapatite (HA)/ TiO2 composite ceramic coatings were formed by micro-arc oxidation (MAO) on pure titanium in mixed electrolyte of calcium glycerophosphate and calcium acetate with DC pulse power. Microstructure, phase composition, porosity and thickness of the coatings were examined using SEM, XRD, Image-Pro Plus 6.0 Image analysis system and Eddy current thickness gauge. Results indicate that MAO coatings containing calcium and phosphorus were formed in situ on pure titanium surface. Pores formed by the discharge channels distribute uniformly on the coatings surface, and the inner layer is dense. The principal crystalline phases of the MAO coatings are anatase TiO2, rutile TiO2, HA, Ca3(PO4)2 and matrix Ti. The interface is metallurgical bonding and the bonding strength is strong. And reaction time makes a greater influence than voltage in thickness and voltage makes a greater influence than time in porosity.

Effects of Surface Treatment on the Microstructural and Crystallographic Changes of Dental 3Y-TZP Ceramic

Objective: To investigate the effects of different surface treatments on the microstructural and crystallographic changes of dental 3Y-TZP ceramics. Methods: 21 pieces of zirconia specimens (15 ´ 15 ´ 1.5 mm) were prepared and divided into 7 groups: control group; grinding group; polishing group; sandblasting group; sandblasting + veneer porcelain sintering group; sandblasting + veneer porcelain sintering twice group and sandblasting + annealing group. The crystal structure of specimen was monitored by X-ray diffraction (XRD) before morphological observation with scanning electron microscope. Results: monoclinic phase increased after grinding while decreased little after polishing, bigger phase change presented after sandblasting compared with decreased phase change induced by veneer porcelain sintering; annealing eradicated the surface m phase. Grinding produced coarse scratches on the surface of samples with removal of surface particles; after grinding and polishing to 7 um level, the surface particles were removed massively, and the surface became smooth with remaining scare scratches and substantial micro cracks. Sandblasting removed scratches near completely producing coarse and irregular surface of samples. Conclusions: Grinding, sandblasting and polishing could produce the transition of Zirconia Ceramic surface from t to m phase. It is better to use heat treatment after mechanical treatment to reverse the changed surface phase.

Effects of Aging on the Mechanical Properties of Dental Pigmented 3Y-TZP Ceramics

The purpose of this study was to investigate the structure, mechanical and low temperature aging properties of colored dental zirconia ceramics. Colored 3Y-TZP zirconia dental zirconia ceramics were made by mixing colorants and their combinations into a 3Y-TZP powder, the green body were compacted at 200MPa, presinter at 1050°C and densely sintered at 1500°C for 2h. Specimens were subjected to an accelerated aging test carried out in an autoclave in steam at 134°C, 2bar, for 4hs. XRD was used to identify the crystal phases, three-point bending strength were tested before and after aging according to the ISO 6872 standard, polished and aging specimens were observed by Atomic Force Microscopy (AFM) to evaluate surface microstructure. Tetragonal-to-monoclinic phase transformation was detected for both uncolored and colored specimens, the relative content of monoclinic phase was increased with the prolonged aging time. Aging had no significant negative effects on flexural strength on colored 3Y-TZP. The nucleation and growth of monoclinic phase were detected by AFM in surface of both colored and uncolored zirconia.

Effect of Pigmentation on Strength of Dental Y-TZP/Porcelain Bilayered Structure

The purpose of this study was to investigate the effect of pigmentation on the flexural strength of dental Y-TZP/porcelain layered structure. KaVo™ Everest zirconia substructures was pigmented by dipping presintered blocks in coloring solution, and colored TZ-3YS zirconia substructures were fabricated by adding pigments before isostatically pressing. Specimens were made in monolithic or bilayered forms. The bending strength was tested. XRD and SEM with EDX were used to analyze the characteristics of the surface structure. Experimental results showed that there were significant differences of bending strength in both zirconia systems between white and colored monoclinic materials, which also in bilayered structures. Pigmentation has no apparent effects on the bonding strength between veneering porcelain and zirconia. Both coloring methods are appropriate when the concentration of pigments is under deliberate controlled.

Study on Dental Colored Zirconia Restoration

This paper explored the color and mechanical properties of CeO2 and Er2O3 shaded zirconia ceramics for dental application. Twelve kinds of colored dental ZrO2 powders were prepared. Experimental results showed that the hue of the materials shift from yellow-green to yellow-red with the increasing concentration of the CeO2 and Er2O3, while reducing of the brightness( L* ) value was little. Three-point bending strength decreased form 1209MPa to 845MPa after coloring, which was lower than the uncolored materials (1301MPa). The fracture toughness decrease slightly. SEM observation revealed more porous microstructure in specimen containing both two additives. Cerium oxide and erbium oxide are candidates of color additives for shading dental zirconia ceramics.

Self-Setting Biphase Porous Calcium Phosphate Cement

This work has achieved a novel self-setting biphase porous calcium phosphate cement (CPC). This biphase porous CPC is mainly formed by α-tricalcium phosphate (α-TCP) and β-tricalcium phosphate (β-TCP). The influence of the weight percent (wt%) of β-TCP of the powder was studied. The setting time is mainly 10-30min, and increasing with the weight percent of β-TCP. Powder ray diffraction (XRD) analysis showed that most α-TCP have turned to low-crystallinized HA after immersed in Simulated Body Fluid (SBF) of 37°C for 7 days. SEM observation showed that the resultants are mainly formed with micropores and microcrystallites, and more micropores turned out in cements with more β-TCP after immersed in SBF for 8 weeks.

Preparation of Porous Hydroxyapatite Scaffolds

Porous hydroxyapatite (HA) ceramic scaffolds were prepared using three-dimensional (3-D) gel-lamination technology with sodium lauryl sulfate as foaming agent and lauryl as foaming stabilizing agent. With gelling system of sodium alginate and calcium chloride, the foamy HA slurry was gelled layer by layer on the 3-D gel-lamination machine to prepare the porous ceramic scaffolds. The viscosity of the foamy ceramic slurry was examined. After sintering, the porous HA bioceramic was characterized in terms of the porous microstructure and mechanical properties. The experimental results demonstrated that the resultant porous ceramic with appropriate pore size, porosity characters, mechanical properties and bioactivity could be obtained.