BACKGROUNDThe low-temperature resistance aging performance of Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) is the key effective factor that influences the long-term success rate of prosthesis. The objective of this study was to test and compare the aging performances for resisting low temperature of Lava Frame, Cercon Smart, and Upcera Yttria-stabilized zirconia core materials, via analyzing the micro and the crystal phases of the materials, and measure the three-point bending strength and the fracture toughness.

METHODSThe three zirconia green bodies were prepared as 60 test samples for three-point bending strength and as 60 test samples for fracture toughness. The test samples for three-point bending strength and fracture toughness were assigned to five groups and were treated respectively for 0, 5, 10, 15, and 20 hours to observe the micro and the crystal phases of the test samples. Then the three-point bending strength and fracture toughness were tested by X-ray diffraction (XRD).

RESULTSThe m phase content of Lava Frame was raised from 7.70% to 13.01%; the m phase content of Cercon Smart was raised from 4.95% to 8.53%; and Lava Frame is raised from 10.84% to 35.18%. The three-point bending strengths of the three zirconia core materials were higher than 1100 MPa and the fracture toughness was higher than 3 MPa·m(1/2). The three-point bending strength and the fracture toughness of Upcra zirconia decreased the most, followed by Lava Frame, and then by Cercon Smart.

CONCLUSIONThe aging resistance sequences of the three zirconia core materials are, from strong to weak, Cercon Smart, Lava Frame, and Upcera.

Ceramics ; chemistry ; Dental Porcelain ; chemistry ; Microscopy, Electron, Scanning ; Temperature ; X-Ray Diffraction ; Yttrium ; chemistry ; Zirconium ; chemistry

OBJECTIVETo prepare zirconia toughened nano-composite alumina ceramic powder for dental application. Physical and chemical property of the prepared material were tested, and the effect of development technology on composite powder was also studied in this study.

METHODSNano-composite alumina powder was prepared by surface-induced precipitation method. The effect of pH value and dispersing agent content on volume of alumina suspension sediment was recorded. The effect of ultrasonic time on agglomeration was measured also. X ray diffraction (XRD) was used to analyze powder phase before and after the stabilizer was added. Scanning electronic microscope (SEM) was applied for characterizing the specimen.

RESULTSThe dispersion was better at pH=9 and wt (dispersing agent) = 0.2% approximately 0.3%. Selecting proper ultrasonic time can decrease the agglomeration of powders and lower the average particle size. XRD analysis indicated that the phase composition of the prepared nano-composite ceramic powder was shown as alpha-Al2O3, t-ZrO2 and a small amount of m-ZrO2 after the addition of stabilizer. Through SEM observation, nanometer-sized ZrO2 particles (80 approximately 100 nm) were uniformly located on the surface of submicrometer alumina grains.

CONCLUSIONSBy choosing appropriate preparation method, weakly agglomerated powders with fine particle size can be obtained. The zirconia part of nano-composite powder was transmitted to partially stabled zirconia after the use of stabilizer.

Aluminum Oxide ; chemistry ; Dental Porcelain ; chemistry ; Hydrogen-Ion Concentration ; Powders ; Zirconium ; chemistry

OBJECTIVETo investigate the influence of mold temperature on the mechanical properties of Ti-Zr alloy castings.

METHODSTi-Zr alloy was cast into a mold which was made of a zircon (ZrO2.SiO2) investment with a casting machine (China) designed as vacuum, pressure and centrifuge. At three mold temperatures (room temperature, 300 degrees C, 600 degrees C) the Ti-Zr alloy was cast separately. The ultimate tensile strength (sigmab), 0.2% offset yield point strength (sigma0.2), and elongation to fracture (delta) were determined by a universal testing machine with 15 mm pre-marked gauge interval. The surface micro-structures of Ti-Zr alloy castings at three mold temperatures were observed by optical microscope.

RESULTSAt a higher mold temperature during casting, the tensile strength and yield strength of Ti-Zr alloy were significantly increased, while the elongations were significantly decreased. The micro-structure of the surface was different from the inner part. There was a reacted layer in the outermost surface. The thickness of reacted layers at the three mold temperatures was about 35.5 man (room temperature), 55.0 microm (300 degrees C) and 65.5 microm (600 degrees C), respectively. The inner part of microstructure composed of main a phases within the prior alpha grain boundaries.

CONCLUSIONThe mold temperature is one of the major factors influencing Ti-Zr alloy mechanical properties. Comparing with Ti6Al4V alloy and Co-Cr alloy castings, Ti-Zr alloy is more suitable for denture frame.

Dental Alloys ; chemistry ; Dental Casting Technique ; Temperature ; Titanium ; chemistry ; Zirconium ; chemistry

OBJECTIVETo investigate the effects of sintering temperature on the physical and mechanical properties of dental zirconia toughened ceramic (ZTC).

METHODS3 mol% yttria-stabilized zirconia compacts were prepared by dry press method and then sintered at 1,490 degrees C, 1,530 degrees C, 1,570 degrees C and 1,610 degrees C respectively. The physical properties and bending strength were then measured.

RESULTSThe result of the study indicated along with the rise of sintering temperature density and shrinkage of ZTC increased, but the pore structure decreased. It also showed the peak of bending strength was in 1,570 degrees C.

CONCLUSIONSIn terms of sintering temperature and bending strength among the selected temperature, the best sintering temperature of 3 mol% yttria-stabilized zirconia should be about 1,570 degrees C.

Dental Porcelain ; chemistry ; Hardness ; Temperature ; Tensile Strength ; Yttrium ; chemistry ; Zirconium ; chemistry

OBJECTIVEThe fabrication of all-ceramic dental restorations is challenged by ceramics' relatively low flexural strength and intrinsic poor resistance to fracture. This paper aimed at investigating the relationships between powder-size gradation and mechanical properties of Zirconia toughened glass infiltrated nanometer-ceramic composite (Al(2)O(3)-nZrO(2)).

METHODSAl(2)O(3)-nZrO(2) ceramics powder (W) was processed by combination methods of chemical co-precipitation and ball milling with addition of different powder-sized ZrO(2). Field-emission scanning electron microscopy was used to determine the particle size distribution and characterize the particle morphology of powders. The matrix compacts were made by slip-casting technique and sintered to 1,450 degrees C and flexural strength and the fracture toughness of them were measured.

RESULTS1. The particle distribution of Al(2)O(3)-nZrO(2) ceramics powder ranges from 0.02 - 3.5 micro m and among them the superfine particles almost accounted for 20%. 2. The ceramic matrix samples with addition of nZrO(2) (W) showed much higher flexural strength (115.434 +/- 5.319) MPa and fracture toughness (2.04 +/- 0.10) MPa m(1/2) than those of pure Al(2)O(3) ceramics (62.763 +/- 7.220 MPa; 1.16 +/- 0.02 MPa m(1/2)).

CONCLUSIONSThe particle size of additive ZrO(2) may impose influences on mechanical properties of Al(2)O(3)-nZrO(2) ceramics matrix. Good homogeneity and reasonable powder-size gradation of ceramic powder can improve the mechanical properties of material.

Aluminum Oxide ; chemistry ; Dental Porcelain ; chemistry ; Hardness ; Nanomedicine ; Nanotechnology ; Particle Size ; Powders ; Tensile Strength ; Zirconium ; chemistry

The aim of this study was to determine if accelerated aging of porcelain veneering had an effect on the surface properties specific to a tetragonal-to-monoclinic transformation (TMT) of zirconia restorations. Thirty-six zirconia samples were milled and sintered to simulate core fabrication followed by exposure to various combinations of surface treatments including as-received (control), hydrofluoric acid (HF), application of liner plus firings, application of porcelain by manual layering and pressing with firing, plus accelerated aging. The quantity of transformed tetragonal to monoclinic phases was analyzed utilized an X-ray diffractometer and one-way analysis of variance was used to analyze data. The control samples as provided from the dental laboratory after milling and sintering process had no TMT (Xm = 0). There was an effect on zirconia samples of HF application with TMT (Xm = 0.8%) and liner plus HF application with TMT (Xm = 8.7%). There was an effect of aging on zirconia samples (no veneering) with significant TMT (Xm = 70.25%). Both manual and pressing techniques of porcelain applications reduced the TMT (manual, Xm = 4.41%, pressing, Xm = 11.57%), although there was no statistical difference between them. It can be concluded that simulated applications of porcelain demonstrated the ability to protect zirconia from TMT after aging with no effect of a liner between different porcelain applications. The HF treatment also caused TMT.
Dental Porcelain ; chemistry ; Surface Properties ; X-Ray Diffraction ; methods ; Zirconium ; chemistry

OBJECTIVETo evaluate the effect of Fe2O3 and CeO2 as colorants on yttria stabilized tetragonal zirconia poly-crystals (Y-TZP) powder.

METHODSThe spray granulation slurry of colored zirconia was prepared with different concentrations of Fe2O3 (0.15%) and CeO2 (4%), which were added in Y-TZP. Zirconia powder was made by spray granulation. The powder specimens were divided into three groups: uncolored zirconia, Fe2O3 (0.15%) zirconia, and CeO2 (4%) zirconia. The particle morphologies of the powder specimens were measured with a laser particle size analyzer and an optical microscope.

RESULTSThe differences in D50 among the three groups were statistically significant (P<0.05). Group Fe2O3 showed a significant difference from groups CeO2 and uncolored zirconia (P<0.05). Group uncolored zirconia showed no significant difference from group CeO2 (P>0.05). Mostly spherical powder was observed in the three groups.

CONCLUSIONFe2O3 as a colorant can affect particles, whereas CeO2 has no effect.

Color ; Dental Stress Analysis ; Ferric Compounds ; Humans ; Materials Testing ; Yttrium ; chemistry ; Zirconium ; chemistry

OBJECTIVETo study the measures for preventing and controlling the pollution of aqueous extract of Astragali Radix proceeded with inorganic ceramic membrane micro-filtration, in order to find effective measures for preventing and controlling the membrane pollution.

METHODThe resistance distribution, polymer removal and changes in physical and chemical parameters of the zirconium oxide film of different pore diameters were determined to analyze the state or location of pollutants as well as the regularity of formation. Meanwhile, recoil and ultrasonic physical measures were adopted to strengthen the membrane process, in order to explore the methods for preventing and controlling the membrane pollution.

RESULTWhen 0.2 microm of ZrO2 micro-filtrated aqueous extract of Astragali Radix, the rate of pollution was as high as 44.9%. The hole blocking resistance and the concentration polarization resistance were the main filtration resistances, while the surface deposit resistance decreased with the increase in the membrane's hold diameter; after micro-filtration, the liquid turbidity significantly reduced, with slight changes in both pH and viscosity. The 0.2 microm ZrO2 micro-filtration membrane performed better than the 0.05 microm pore size membrane in terms of conductivity. The 0. 2 microm and 0.05 microm pore diameter membranes showed better performance in the removal of pectin. The ultrasonic measure to strengthen membranes is more suitable to this system, with a flux rate up by 41.7%.

CONCLUSIONThe membrane optimization process adopts appropriate measures for preventing and controlling the membrane pollution, in order to reduce the membrane pollution, recover membrane performance and increase filtration efficiency.

Astragalus Plant ; chemistry ; Ceramics ; chemistry ; Drug Contamination ; Drugs, Chinese Herbal ; chemistry ; Filtration ; methods ; Membranes, Artificial ; Technology, Pharmaceutical ; Zirconium ; chemistry

Variation in pH value of oral cavity circumstance causes decayed tooth. In this paper, corrosions of Ti-Fe-Mo-Mn-Nb-Zr dental alloys in various pH lactic acids were studied by immersion test. In the case of pH=4, which is an acidity slightly larger than that causes decayed tooth, Ti-Fe-Mo-Mn-Nb-Zr alloys are entirely corrosion-resistant, and the corrosion type is pitting. With the increase in acidity, the corrosion-resistance of Ti-Fe-Mo-Mn-Nb-Zr alloys deteriorates, and the corrosion type changes from pitting to intergranular corrosion. Fe ion is the most dissolved substance in impregnation, which means Fe goes against the corrosion-resistance of Ti alloys. Both results of thermodynamics calculation and X-ray photoelectron spectroscopy have shown that Mn2O3, Nb2O5 and TiO2 form oxide film on the surface of Ti-Fe-Mo-Mn-Nb-Zr alloys.
Corrosion ; Dental Alloys ; chemistry ; Humans ; Hydrogen-Ion Concentration ; Iron ; chemistry ; Lactic Acid ; chemistry ; Manganese ; chemistry ; Molybdenum ; chemistry ; Niobium ; chemistry ; Surface Properties ; Titanium ; chemistry ; Zirconium ; chemistry

Graded Zirconia-hydroxyapatite composite bioceramic and simplex Zirconia-hydroxyapatite composite bioceramic were produced, and the extractes of these two of materials were made to evaluate their immunocompatibility. Scanning electron microscope (SEM) was used to detect the character of the surface of the graded composite bioceramic. Holding and without holding phytohemagglutinin (PHA), proliferation and activation of peripheralblood monocytes(PBMCs) cultured in the two extracts were studied. Cultured in PHA after 72 hours, the proliforation rate of the graded composite group was significantly higher than the simplex composite group (P < 0.01). There was no difference of apoptosis of PBMCs of the two groups (P > 0.05). Cultured in PHA after 24 hours, the ratio of CD3/CD69 positive PBMCs of the simple composite group was significantly higher than that of the graded composite material group (P < 0.01). The numbers of PBMCs activated by the graded composite material group were less than that of the simply composite material group and the technique of graded composite will be helpful to improve its immunocompatibility.
Adult ; Cells, Cultured ; Dental Porcelain ; chemistry ; pharmacology ; Durapatite ; chemistry ; pharmacology ; Humans ; Materials Testing ; Monocytes ; drug effects ; immunology ; Zirconium ; chemistry ; pharmacology