Aluminum-free glass ionomer cements containing 45S5 Bioglass® and its bioglass-ceramic.

Although the incorporation of bioactive glasses into glass ionomer cements (GICs) has led to promising results, using a bioactive glass as the only solid component of GICs has never been investigated. In this study, we developed an Al-free GIC with standard compressive strength using various combinations of 45S5 Bioglass® and its glass-ceramic as the solid component. The glass-ceramic particles with 74% crystallinity were used for this purpose as they can best act as both remineralizing and reinforcing agents. Strengthening mechanisms including crack deflection and crack-tip shielding were activated for the GICs containing 50-50 wt% bioglass and bioglass-ceramic as the optimum ratio. The progression of the GIC setting reaction at its early stages was also monitored and verified. We also discussed that our bimodal particle size distribution containing both micron- and nanosized particles may enhance the packing density and integrity of the structure of the cements after setting. In such GICs produced in this study, the toxic effects of Al are avoided while chemical bonds are expected to form between the cement and the surrounding hard tissue(s) through interfacial biomineralization and adhesion.

Glass ionomer cements with enhanced mechanical and remineralizing properties containing 45S5 bioglass-ceramic particles.

The clinical applications of glass ionomer cements (GICs) are limited by their relatively poor mechanical properties and insufficient remineralizing capacity. In this study, we developed hybrid GICs with improved mechanical and remineralizing properties via incorporation of an optimum amount (5 wt%) of 45S5 bioglass-ceramic particles. Also, we found that bioglass-ceramic particles with 74% crystallinity best act as both remineralizing and reinforcing agents. The degree of crystallinity of the additives, is overlooked in this context in other research. At around 74% crystallinity, there is sufficient amount of combeite and an amorphous phosphorous-rich phase in the 45S5 bioglass-ceramic particles to respectively promote their reinforcing role and allow them to effectively partake in the setting process creating an excellent interfacial bond with the GIC matrix. As a result, several strengthening mechanisms such as crack deflection and crack-tip shielding are activated within the hybrid GIC containing 5 wt% bioglass-ceramic with 74% crystallinity, contributing to its improved mechanical properties. The enhanced remineralizing and mechanical properties of such hybrid GICs can potentially improve their in vivo performance and broaden their clinical applications.

Morphology of Aluminum Alloy Foams Produced with Dolomite via Partial Sintering of Precursors.

Highly expanded, low-cost aluminum-based foams were successfully produced via powder metallurgy using dolomite as foaming agent. Nickel additions (5-15 wt.%) were explored in order to reduce the temperature disparity between dolomite decomposition and the melting range of the metallic matrix. Specific Al-Ni compositions provide appropriate viscosities for effective encapsulation of CO2 gas released during dolomite decomposition. A partial sintering step of compacted precursors was introduced prior to foaming, which resulted in high porosity levels (~86%) and significant volume expansion (~250%) in the final product. The partial sintering technique was a key determining factor in obtaining stable, highly expanded cellular structures with homogeneous pores, averaging 3 mm in size and being morphologically comparable with ALPORASTM foams.

Morphological examination of highly porous polylactic acid/Bioglass® scaffolds produced via nonsolvent induced phase separation.

In this study, we produce highly porous (up to ∼91%) composite scaffolds of polylactic acid (PLA) containing 2 wt % sol-gel-derived 45S5 Bioglass® particles via nonsolvent induced phase separation at -23°C with no sacrificial phases involved. Before the incorporation of the bioglass with PLA, the particles are surface modified with a silane coupling agent which effectively diminishes agglomeration between them leading to a better dispersion of bioactive particles throughout the scaffold. Interestingly, the incorporation route (via solvent dichloromethane or nonsolvent hexane) of the surface modified particles in the foaming process has the greatest impact on porosity, crystallinity, and morphology of the scaffolds. The composite scaffolds with a morphology consisting of both mesopores and large macropores, which is potentially beneficial for bone regeneration applications, are examined further. SEM images show that the surface modified bioglass particles take-up a unique configuration within the mesoporous structure of these scaffolds ensuring that the particles are well interlocked but not completely covered by PLA such that they can be in contact with physiological fluids. The results of preliminary in vitro tests confirm that this PLA/bioglass configuration promotes the interaction of the bioactive phase with physiological fluids. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2433-2442, 2017.

Synthesis of 45S5 Bioglass® via a straightforward organic, nitrate-free sol-gel process.

More than four decades after the discovery of 45S5 Bioglass® as the first bioactive material, this composition is still one of the most promising materials in the tissue engineering field. Sol-gel-derived bioactive glasses generally possess improved properties over other bioactive glasses, because of their highly porous microstructure and unique surface chemistry which accelerate hydroxyapatite formation. In the current study, a new combination of precursors with lactic acid as the hydrolysis catalyst have been employed to design an organic, nitrate-free sol-gel procedure for synthesizing of 45S5 Bioglass®. This straightforward route is able to produce fully amorphous submicron particles of this glass with an appropriately high specific surface area on the order of ten times higher than that of the melt-derived glasses. These characteristics are expected to lead to rapid hydroxyapatite formation and consequently more efficient bone bonding.