OBJECTIVETo compare the retention of selected cores to all-ceramic posts in post-and-core system, in which the ceramic core was combined with the post by direct sintering, adhering, and the composite resin core was formed onto the post.

METHODSA total of 15 all-ceramic post fabricated by alumina-zirconia nano-composite infiltrated ceramics were divided into three groups. In group A, forming and combining the ceramic core with the post by direct sintering. In group B, combining the ceramic core with the post by adhering. In group C, forming composite resin core onto the post. Each specimen was placed into a special jig along the post axis and subjected to a load on INSTRON 4302 universal testing instrument until failure.

RESULTSThere was a statistically significant difference between the groups (P < 0.01). Group A showed a significantly higher retention which was 3.04 and 2.88 times as high as group B and C respectively (P < 0.01). There was no significant difference between adhering and composite resin core (P> 0.05).

CONCLUSIONA reliable retention of the core to the post can be achieved when the alumina-zirconia nanocomposite infiltrated ceramic core is formed and combined with the post by direct sintering, which offers significantly higher retention than adhering and forming composite resin core onto the post.

Aluminum Oxide ; Ceramics ; Composite Resins ; Dental Porcelain ; Dental Restoration Failure ; Humans ; Materials Testing ; Post and Core Technique ; Zirconium

OBJECTIVETo investigate the effects of Sol-Gel coating on the corrosion resistance of nickel-chronium alloys in vitro.

METHODSThe bond strength of coating-substrate interface sintered at different temperatures (300, 400, 500, 600 degrees C) was tested by scratching method. The Sol-Gel coating was analyzed by scanning electron microscope (SEM), and its corrosion resistance was assessed by a static immersion method.

RESULTSThe bond strength of coating-substrate interface reaches the peak at 400 degrees C. The Sol -Gel coating can apparently inhibit the release of metal ions and improve the corrosion resistance of nickel-chromium alloy.

CONCLUSIONSol-Gel coating can evidently improve corrosion resistance of the nickel-chromium alloy, which has great potential in prospective clinical practice.

Alloys ; Chromium Alloys ; Corrosion ; Dental Alloys ; Humans ; Nickel ; Polymethyl Methacrylate ; Prospective Studies

OBJECTIVETo prepare zinc-modified carbonated hydroxyapatite (Zn-CHA) coating material via sol-gel method and explore the influence of zinc substitution on physical and chemical properties of biomaterial samples.

METHODSTwo kinds of samples with different zinc content and Ca/P molar ratio were prepared. One was fabricated with 4% zinc and the Ca/P molar ratio was 1.67. Another was prepared with 8% zinc and the (Ca+Zn)/P molar ratio was 1.67. The coating samples were characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM). Furthermore, the zinc ions releasing ability of the coating samples were investigated by atomic absorption spectroscopy (AAS).

RESULTSXRD results revealed that the coating samples contained hydroxyapatite phase. After determination by FTIR, the biomaterial samples were found to contain carbonate and resemble biological apatites. High homogeneous and porous surfaces of coating samples were observed in SEM micrographs. According to the results of dissolution test, zinc was incorporated into hydroxyapatite lattice structure or surface absorbed when calcium was insufficient or sufficient respectively.

CONCLUSIONThe results demonstrate that phase-pure zinc-modified carbonated hydroxyapatite might be prepared through simple sol-gel method and have favorable antibacterial effect.

Apatites ; Biocompatible Materials ; Durapatite ; Microscopy, Electron, Scanning ; Polymethyl Methacrylate ; Spectroscopy, Fourier Transform Infrared ; X-Ray Diffraction ; Zinc

A in vitro platelet aggregation bioassay was developed for the quality control of XST capsules. The in vitro anti-platelet aggregation effect in rats was observed to detect the bioactivity of XST capsules. Panax notoginseng saponins and Xuesaitong lyophilizedpowder for injection were taken as standard control substances to determine the potency. According to the results, XST capsules showeda significant inhibitory effect on thrombin-induced platelet aggregation in a dose-dependent manner. The in vitro anti-platelet activity oflyophilized powder for injection was stabler than that of Panax notoginseng saponins, and so suitable to serve as a standard control substance. The biological potency of XST capsules compared with standard control substance was detected by using parallel line assay. According to the results, the established bioassay method had a good repeatability (RSD 2.92%). The sample test results could pass thereliability test(linear deviation P > 0.05, parallel deviation P > 0.05). This bioassay method could be used as one of the complementary quality control methods for XST capsules.
Animals ; Capsules ; pharmacology ; Drugs, Chinese Herbal ; pharmacology ; Male ; Panax notoginseng ; chemistry ; Platelet Aggregation ; drug effects ; Platelet Aggregation Inhibitors ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Saponins ; pharmacology

Objective To study the effects of alumina content on sintered density, mechanical property and translucency of zirconia nanocomposite all-ceramics. Methods Specimens of zirconia nanocomposite all-ceramics were divided into five groups based on their alumina content which are 0% (control group), 2. 5% , 5. 0% , 7. 5% and 10. 0% respectively. The sintered densities were measured using Archimedes' method. Specimens' bending strengths were measured with three-point bending test( ISO 6872). The visible light transmittances were measured with spectrophotometric arrangements and the fractured surfaces were observed using scanning electron microscope (SEM).Results The control group of pure zirconia could be sintered to the theoretical density under pressure-less sintering condition. The bending strength was (1100.27 ±54.82) MPa, the fracture toughness was (4.96 ±0.35) MPa·m1/2 and the transmittance could reach 17. 03%. The sintered density and transmittance decreased as alumina content increased from 2. 5% to 10%. However, the fracture toughness only increased slightly. In all four alumina groups, the additions of alumina had no significant effect on samples' bending strengths (P >0. 05). When the content of alumina was 10% , fracture toughness of specimens reached (6. 13 ±0.44) MPa·m1/2 while samples' transmittance declined to 6. 21 %. SEM results showed that alumina particles had no significant effect on the grain size and distribution of tetragonal zirconia polycrystals. Conclusions Additions of alumina to yttria-tetragonal zirconia polycrystals could influence its mechanical property and translucency. Additions of the other phase to zirconia ceramics should meet the clinical demands of strength and esthetics.

OBJECTIVEThe objective of this study is to investigate the influence of zirconia content which is 0-30.0% weight percentage of matrix on translucency of zirconia-toughened alumina glass-infiltrated ceramics.

METHODSSeven groups were divided according to different weight percentage of zirconia (0, 2.5%, 5.0%, 7.5%, 10.0%, 20.0% and 30.0%). After sintering, infiltrating and polishing, spectral transmittance was determined with spectrophotometer under D65 standard source. Contrast ratio was also tested by whiteness colorimeter.

RESULTSWith mass fraction of zirconia increasing from 0 to 30.0%, spectral transmittance reduced from 0.406% to 0.058%, while contrast ratio value increased from 0.849 +/- 0.005 to 1.015 +/- 0.006. When zirconia content was 10.0%, contrast ratio was 0.990 +/- 0.008. When it was more than 10.0%, transmission rate of the downward trend and contrast ratio of the rising trend became flat.

CONCLUSIONZirconia content has a direct impact on translucency of zirconia-toughened alumina glass-infiltrated ceramic, which is essentially opaque when zirconia content is 10.0%. When mass fraction of zirconia is more than 10.0%, the influence of zirconia content is reduced.

Aluminum Oxide ; Ceramics ; Dental Materials ; Dental Porcelain ; Glass ; Zirconium

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

OBJECTIVETo investigae the function of the glass colorant on the color of the machinable infiltrated ceramics(MIC).

METHODSFive kinds of glass with different colorant were infiltrated through the aluminous matrix by heating the components to 1 100 degrees C for 2 hours. The specimens surface was polished, and their thickness was 0.5 mm.

RESULTSThe refractive index of the MIC infiltration glass was 1.59691 (587.6 nm, nd) . The most different parameter of the MIC color were L*, then a*, and b* had little difference . The parameters of the color space of MIC were: L*(64.55-71.46), a*(3.35-7.38), b*(10.00-12.41), Ca*b*(11.38-13.95), ha*b*(54.07-73.00). These were almost close to the color parameters of Vita In-ceram.

CONCLUSIONThis experiment proved that the glass colorant was changed the MIC color parameters, and the main function was on L*, then a*. The ceramic color was up to the requirement of clinic.

Aluminum Oxide ; Ceramics ; Color ; Dental Materials ; Dental Porcelain ; Glass ; Humans

OBJECTIVETo evaluated the cytotoxicity of a new nano-hydroxyapatite (n-HA) root canal sealer.

METHODSIn this study, the cytotoxicity was evaluated by the method of MTT assay in vitro, and culture medium F12 as control, three concentrations of the soaking material cultured with mouse osteoblast separately, to test the cell relative growth rate (RGR) of every group.

RESULTSThe toxicity graduation of the n-HA root canal sealer tends to 0 with the culture time increasing. The cell survival rate of n-HA root canal sealer showed high relatively. The OD value of cell was similar for the negative control and the extracts (P > 0.05).

CONCLUSIONThe result indicated that n-HA root canal sealer was compatible with the testcells.

Animals ; Cell Survival ; Dental Pulp Cavity ; Durapatite ; Mice ; Root Canal Filling Materials ; Zinc Oxide-Eugenol Cement

OBJECTIVETo study the cell biocompatibility of porous biphasic calcium phosphate nanocomposite in vitro.

METHODSBone marrow mesenchymal cell (BMSCs) obtained from SD rat bone marrow were in vitro induced and proliferated. Afler their osteoblast phenotypes were verified, BMSCs were seeded onto prepared porous biphasic calcium phosphate nanocomposite (Experiment group) and common porous hydroxyapatite (Control group). The cell adhesion was evaluated by scanning electron microscope. Synthesis of alkaline phosphatase enzyme (ALP) and osteocalcin were detected and cell cycle was detected by flow cytometry.

RESULTSBMSCs could fully attach to and extend on the material in experiment and control group, Moreover, experiment group were superior to control group in adhesion, proliferative abilities and osteogenic activity.

CONCLUSIONBMSCs can differentiate to osteoblast phenotype; the porous biphasic calcium phosphate nanocomposite as bone tissue engineering scaffold has good cell biocompatibility.

Alkaline Phosphatase ; Animals ; Bone Marrow Cells ; Bone and Bones ; Cell Adhesion ; Durapatite ; Hydroxyapatites ; Materials Testing ; Nanocomposites ; Osteoblasts ; Osteocalcin ; Rats ; Tissue Engineering ; Tissue Scaffolds