Papers by Keyword: Zirconia

Abstract: The measurement of temperature based on the characteristic lifetime decay in luminescence intensity of dopant ions following excitation is described with illustrations drawn from europium doping in yttria-stabilized zirconia. The method is particularly attractive for making measurements in a temperature gradient, such as those in thermal barrier coatings.

Abstract: Porous biomaterials including porous bioceramics play important roles for hard tissue replacement and regeneration. I this paper, porous alumina (with and without zirconia addition) ceramics were produced via coating polyurethane (PU) foams with Al2O3 (ZrO2) slurries, followed by drying at room temperature and sintering at 1300 oC. The advantage of the PU foam method was the achieved high pore interconnectivity, but the mechanical properties of the porous ceramics were rather poor due to the high macroporosity and the high microporosity. To remove the microporosity and strengthen the porous alumina ceramics, a lanthanum-modified aluminosilicate (LAS) glass was used to infiltrate the alumina struts. Nevertheless, the resulting LAS-modified macroporous alumina ceramics would have no ability to bond to bone tissues. To impart a bioactivity (i.e. the ability of bone bonding) to the bioinert porous ceramics, a bioactive glass layer was applied by dipping with the bioactive glass slurry and sintering at 1200 oC. The twice coated porous alumina ceramics would exhibit high compressive strengths, allow bone tissue ingrowth, and form strong bonematerial integration. A biodegradable filler – calcium phosphate cement was also incorporated. A possible application of the porous bioceramics would be for the maxillofacial reconstruction.

Abstract: In the present study, zirconia ceramic was ground with a resin-bonded diamond wheel on a precision surface grinding machine. Grinding temperatures generated at the wheel-workpiece contact zone were measured using a sandwiched foil thermocouple, and the net consumed grinding powers were also measured. The energy partition to the diamond abrasives was estimated using measured grinding temperatures and powers. Based on the energy partition values obtained from the analyzed results, the diamond tip temperature was calculated and found to be over 1000°C if the circular grain contact of radius was less than a critical value for ductile field grinding of zirconia ceramic.

Abstract: When producing implant materials, achievement of optimal bioactivity and biocompatibility are essential. Nanocoatings can provide an efficient cost effective way to alter the interactions of the implant material with its destined “host” environment. Nanocoatings of sol-gel derived carbonated hydroxyapatite (HAp) and zirconia were produced in this study. The surfaces were characterised by Fourier transform infrared spectroscopy (FTIR) and light microscopy. Cell adhesion, proliferation and viability, as well as expression of alkaline phosphatase (ALP is an indicator of bone formation) were assessed as indicators of biocompatibility. Our results have shown that sol-gel derived nano crystalline HAp acts as an ideal surface for implant coatings.

Abstract: In the present study, ZrO2 was added into the injectable calcium phosphate cements (CPCs) to improve their mechanical strength. Different mass fractions of ZrO2 (5 %, 10 %, 15 %, 20%) were mixed with the powder components consisted of tricalcium phosphate (α-TCP) and hydroxyapatite (HA). Then formed the paste via adding the liquid component consisted of citric acid. The compressive strength, the injectability, the initial setting time and finial time of CPC were measured, respectively. X-ray diffraction (XRD) was employed to analyse the phase of as-prepared CPC. Scanning Electron Microscope (SEM) and Energy dispersive spertrum (EDS) were used to observe the morphology and indicate the element components of CPC. The compressive strength of ZrO2-CPC was higher than that of CPC without added ZrO2. The compressive strength got the maximal when the mass fraction of ZrO2 was 15%. It had no effect on the injectability with adding ZrO2, which were 89 % to 92 %. It had a slight down-regulation of the initial and final setting time with adding ZrO2. SEM showed that there was amounts needle-like substance in CPC, which might be related to the improvement of compressive strength of CPC. XRD showed that there were HA, a few of α-TCP and ZrO2 diffraction peaks in CPCs. The present results indicate that it is feasible to improve the compressive strength of injectable CPC via adding ZrO2.

Abstract: Colloidal processing was used to cast zirconia and hydroxyapatite materials. The cast materials reached densities around 99% when sintered at 1500°C and 1200°C respectively. By controlling the colloidal process the sintered density of hydroxyapatite was also reduced to around 80% when the same sintering condition was used. The casting process was combined with free form fabrication to prepare designed scaffolds with identical macroporosity. These scaffolds were used to evaluate the early bone tissue response in rabbit femur. After six weeks of implantation the bone area in scaffolds of zirconia and hydroxyapatite were compared. In scaffolds of hydroxyapatite the bone area was roughly three times larger compared to corresponding scaffolds of zirconia. When the scaffolds of hydroxyapatite also contained an open microporosity of around 20% the amount of bone was even more pronounced. The results showed the importance of the material composition and the microstructure on the bone regenerating performance of scaffolds.

Abstract: In Vitro Bond strength of base-coated (Y, Fe)-TZPs (yttria and iron co-doped tetragonal zirconia polycrystals) were investigated to evaluate the feasibility for the ceramic bracket applications. Pre-sintered (Y,Fe)-TZP brackets were machined, abraded and spray-coated with granule slurries containing 10~50 wt% of flux. Better adhesion to the base surface of the brackets was observed by raising the amount of flux in the slurries. It may be because of the fusion and the collapse of the granules as a result of the high amount of flux. The one-way analysis of variance indicated that there were significant differences in bond strength measurements between the experimental groups except 30% and 50% flux content groups. The Weibull distribution revealed that 50% flux content group is the best with a high characteristic strength value. Mean ARI values exhibited large differences and ranged from 1.6 for 50% flux content group to 3.0 for non-coated group. Adhesive remnant of adhesive resin was decreased by increasing the flux up to 50%. Reduction in adhesive remnant is likely due to the higher bonding of adhesive resin to granules. No teeth and bracket damages were found in any teeth de-bonded by shear force. The base-coated brackets with higher strength (11.5 MPa) and no adhesive remnant were newly proposed for the orthodontics applications.

Abstract: The aim of this study was to investigate the effect of surface treatments on bonding strength of two kinds of zirconia to three kinds of resin cements. After thermal cycling, the shear bonding strength of both zirconia decreased in all the resin cements. The bonding strengths of two resin cements in which primer contains silane dramatically decreased after the thermal-cycling (p<0.01). Although the surface roughness of both zirconia sandblasted by 125-%m SiC was quite larger than that by 70-%m alumina (p<0.05), there were no significant differences in the bonding strength of the resin cement to both zirconia sandblasted by 70-%m Al2O3 and 125-%m SiC (p>0.05).

Abstract: The aim of this study was to evaluate the biocompatibility with the proliferation of osteoblast-like cell (MC3T3-E1) on zirconia/alumina nanocomposite (NANOZR) in comparison to yttria stabilized zirconia (3Y-TZP) and titanium (Ti). Cellular proliferations after 1-, 3-, 6-, and 9-day incubation were calculated from the measurement of the MTT activities of the proliferated cell and were analyzed by two-way ANOVA. Time-dependent proliferation of MC3T3-E1 in all the sample was observed in all three materials with culture days. However, these were no significant differences in the proliferation between three kinds of material, indicating all the materials have a similar-good biocompatibility.