Deposition of Hydroxyapatite on Silica Made from Rice Husk Ash to Produce the Powder Component of Calcium Phosphate Cement

Hydroxyapatite (HA) has been deposited on silica (SiO2) particles to produce HA-SiO2 composite that will be used as the powder component of calcium phosphate cement. HA was expected to be on the composite surface to maintain its bioactivity. SiO2 was made by the sol-gel method, in which silicate solution was extracted from rice husk ash with NaOH solution. Deposition of HA on SiO2 was carried out by wet chemical deposition method at various Ca/Si molar ratio (in a range of 5–25) followed by calcination at 600 °C for 2 h. Results showed that HA was successfully deposited on SiO2 particles. The cell parameters of the HA crystals were slightly distorted by the presence of SiO2 and HA in the composite had a bigger cell volume than pure HA. The crystallite size of HA in the composites increased with the increase of the Ca/Si ratio but the values were smaller than pure HA. SiO2 acted as a morphology directing agent. At low Ca/Si ratio, the HA-SiO2 particles were in a form of short rod-like particles with sizes of < 50 nm, while at high Ca/Si ratio, a mixture of short and long rod-like particles with the size of < 100 nm was obtained. The zeta potential of composites was almost similar to pure HA. These properties indicated that HA-SiO2 composites support the bioactivity of injectable calcium phosphate cement.

Melting ranges of heterophase systems Zr – Si – ZrB2 – ZrSi2-MoSi2 and Zr – Si – HfB2 – HfSi2 – MoSi2

The work is devoted to studying the melting ranges of the base Zr – Si eutectic composition depending on the content of the heterophasic powder component in the ZrB2 – ZrSi2 – MoSi2 and HfB2 – HfSi2 – MoSi2 systems in an amount of 30 – 90 % obtained by the method of self-propagating high-temperature synthesis (SHS). The melting range of the mixture Zr – Si was 1420 – 1440 °C, while the addition of SHS-powders ZrB2 – ZrSi2 – MoSi2 led to an increase in the melting onset temperature Тmelt.onset to 1460 – 1560 °С and the complete melting temperature Tmelt.complete to 1480 – 1670 °C. The addition of HfB2 – HfSi2 – MoSi2 powders had a weak effect on the values of Тmelt.onset (1390 – 1430 °С), but led to an increase in the values of Tmelt.complete to 1510 – 1550 °С. X-ray phase analysis showed that the remelted samples contained ZrB2/HfB2, ZrSi2/HfSi2, MoSi2 phases and Si, with the number of phases being directly proportional to the content of SHS powders in the composition of the Zr – Si mixture. The ingots were characterized by a homogeneous structure consisting of a silicon matrix, ZrSi2/HfSi2, MoSi2 disilicide grains, with ZrB2/HfB2 diboride inclusions.

Novel Nanotechnology of TiO2Improves Physical-Chemical and Biological Properties of Glass Ionomer Cement

The aim of this study was to assess the performance of glass ionomer cement (GIC) added with TiO2nanotubes. TiO2nanotubes [3%, 5%, and 7% (w/w)] were incorporated into GIC’s (Ketac Molar EasyMix™) powder component, whereas unblended powder was used as control. Physical-chemical-biological analysis included energy dispersive spectroscopy (EDS), surface roughness (SR), Knoop hardness (SH), fluoride-releasing analysis, cytotoxicity, cell morphology, and extracellular matrix (ECM) composition. Parametric or nonparametric ANOVA were used for statistical comparisons (α≤0.05). Data analysis revealed that EDS only detected Ti at the 5% and 7% groups and that GIC’s physical-chemical properties were significantly improved by the addition of 5% TiO2as compared to 3% and GIC alone. Furthermore, regardless of TiO2concentration, no significant effect was found on SR, whereas GIC-containing 7% TiO2presented decreased SH values. Fluoride release lasted longer for the 5% and 7% TiO2groups, and cell morphology/spreading and ECM composition were found to be positively affected by TiO2at 5%. In conclusion, in the current study, nanotechnology incorporated in GIC affected ECM composition and was important for the superior microhardness and fluoride release, suggesting its potential for higher stress-bearing site restorations.

Determination Features of the Component Diffusion Coefficients of the Fe-Cr-Ni-Gr Powder Systems Sintering

To predict structuring and to produce Fe-Cr-Ni-Graphite-based powdered alloys with tailor-made properties, the component diffusion coefficients have been determined that allow calculating sintering or homogenizing annealing parameters of heterogeneous charge products. It has been revealed that Fe, Cr and Ni heterodiffusion coefficients are influenced not only by their own concentration, but also by structuring kinetics and the number and distribution of the graphite in charge. The electron-probe test shows the distribution of the components in the in-terparticle contact zones. Using the Motano’s, the Lubov’s and the Maksimov’s methods, the values of mutual diffusion coefficients depending on the component concentration have been determined. Using Darken’s ratios and having experimentally determined the component interparticle zones and the displacement distance, the partial heterodiffusion coefficients have been calculated. The given paper proves that the powder-component grain-size distribution alloys should be selected on the basis of relative values of the heterodiffusion coefficients.

A Study on the Change of Fluorescent Powder Component by Orthogonal Design

This paper explained the basic principles of single factor experiment and orthogonal design which were used to change the component of fluorescent powder and improve latent fingerprint appearing effect on object surface. Besides, the author also commented on the characteristics of optimized formulation.

Newer Glass Ionomer Cements having Strontium Ions and the Effect of their Release on Acidic Medium

ABSTRACT Glass ionomer cements (GICs) are mostly used in restorative dentistry. Their efficacy is enhanced as compared to other direct restorative materials because they release various ions like fluoride (F–), strontium (Sr+2) and calcium (Ca+2) when they are exposed to an acidic environment. Newer GICs often have Sr+2 in place of Ca+2 ions as part of their powder component. Both ions (F– and Sr+2) have a synergistic effect on the remineralization process. These elements are not dependent on each other. Either one has an effect on remineralization. A combination of Sr+2 and F– might provide more benefits than either of these elements individually. An attempt has been made in this article to discuss the composition, setting reaction and bonding mechanism of GIC with the tooth surface and to cover the effects of release of Sr+2 and F– ions from GIC on the tooth structure. How to cite this article Hassan U, Farooq I, Mahdi S, Ullah R, Rana H. Newer Glass Ionomer Cements having Strontium Ions and the Effect of their Release on Acidic Medium. Int J Prosthodont Restor Dent 2012;2(2):57-60.

Flexural Properties of Silorane Bone Cement

There has been little change in the formulation of bone cements since Sir John Charnley first developed them in the 1970s. Bone cements are methacrylate based systems packaged in two components [1]. The powder component contains a mixture of polymethyl methacrylate (PMMA), methyl methacrylate-styrene-copolymer, and a radio opacifier (either barium sulfate or zirconium oxide) [2]. The second component is a liquid monomer typically containing methyl methacrylate, N, N-dimethyl-p-toluidine (activator), and hydroquinone. Flexural strength and flexural modulus of bone cements range between 60–75 MPa and 2.2–3.3 GPa, respectively [3, 4]. ISO 5833 requires bone cements to have a strength greater than 50 MPa and a modulus greater than 1.8 GPa [5].