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Abstract In this paper, a water soluble hydantion epoxy resin (ER) was employed to prepare zirconia green bodies with high mechanical strength via epoxy gel-casting (EGC) for dental applications. The rheological properties and gelation behaviors of the suspensions, and the microstructure and mechanical strength of zirconia were systematically studied. The results revealed that solid loadings of up to 52.0 vol% could be achieved with the addition of 0.8 wt% dispersant. When the concentration of ER in the 52.0 vol% suspensions increased from 10.0 to 25.0 wt%, the mechanical strength of the resulting green bodies was enhanced from 40.96 ± 5.20 to 51.22 ± 12.01 MPa. A rough sketch of a pre-sintered zirconia crown was soft-machined from the green body consolidated from a 52.0 vol% suspension containing 10.0 wt% ER. The sintered body had a high mechanical strength of 942.77 ± 95.61 MPa. Highlights • The hydantion epoxy resin was employed to prepare zirconia green body with high mechanical strength for dental application. • The mechanical strength of zirconia green body was reach to 51.22 ± 12.01 MPa. • Pre-sintered zirconia crown was soft-machined and the sintered body had a high mechanical strength of 942.77 ± 95.61 MPa. [ABSTRACT FROM AUTHOR]

Microspheres with hollow and/or porous structures have been widely used in various applications. A new method of spraying and freezing emulsions was developed to prepare hollow HA (hydroxyapatite) microspheres with interconnected pores by using PVA (polyvinyl alcohol) as emulsifiers and binders. The relationships between viscosity and shear time or rates were tested and the dispersing stability of oil in water (O/W) emulsions was characterized with comparison to suspensions without the addition of oil phase. The effects of solid loadings of HA and the volume ratio between oil and water on the morphologies of microspheres were investigated. Hollow HA microspheres with particle diameter of ~ 20 μm and pore size of ~ 0.6 μm were successfully obtained by spray freezing method. Besides, drying and sintering processes were crucial to the formation of hollow and porous structures, respectively. The gentamicin loading and releasing of HA porous microspheres with different hollow volumes were tested. [ABSTRACT FROM AUTHOR]

Osteoblasts growing into bone substitute is an important step of bone regeneration. This study prepared porous hydroxyapatite (HA)/BaTiO 3 piezoelectric composites with porosity of 40%, 50% and 60% by ice-templating method. Effects of HA/BaTiO 3 composites with different porosities, with and without polarizing treatment on adhesion, proliferation and differentiation of osteoblasts were investigated in vitro. Results revealed that cell densities of the porous groups were significantly higher than those of the dense group ( p < 0.05), so did the alkaline phosphate (ALP) and bone gla protein (BGP) activities. Porosity of 50% group exhibited higher ALP activity and BGP activity than those of the 40% and 60% groups. Scanning electron microscopy (SEM) observations revealed that osteoblasts adhered and stretched better on porous HA/BaTiO 3 than on the dense one, especially HA/BaTiO 3 with porosity of 50% and 60%. However, there was no significant difference in the cell morphology, cell densities, ALP and BGP activities between the polarized group and the non-polarized group ( p > 0.05). The absence of mechanical loading on the polarized samples may account for this. The results indicated that hierarchically porous HA/BaTiO 3 played a favorable part in osteoblasts proliferation, differentiation and adhesion process and is a promising bone substitute material. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HA) microspheres with high porosities were successfully obtained using an improved ice-templated spray drying (ITSD) technique for drug delivery applications. Pore structures and pore sizes of microspheres have great impact on drug loading and release kinetics. Therefore, solvent types, polyvinyl alcohol (PVA) contents and solid loadings of suspensions were adjusted to control the pore structures and pore sizes. Microspheres with interconnected pore networks and aligned pore structures were obtained using camphene-based and tert-butyl alcohol (TBA)-based suspensions, respectively. With the increase of PVA contents in suspensions, the growth of sintering neck became more obvious and the surface of HA particles became smoother. The inner pore structures of microspheres transformed from uniformly distributed cellular pores to three-dimensional interconnected pore networks, with the increase of solid loadings in suspensions. Gentamicin was successfully loaded into porous HA microspheres. The drug loading percentage increased from 40.59 to 49.82% with the increase of porosity of HA microspheres. The release percentage during the initial 18 h increased from 48.72 to 65.68% with the transformation of pore structures from independent cellular pores (main diameter ~ 3 μm) to three-dimensional interconnected pore networks (main diameter > 3 μm). [ABSTRACT FROM AUTHOR]

Abstract: It was proposed that the piezoelectric effect played an important physiological role in bone growth, remodelling and fracture healing. An aligned porous piezoelectric composite scaffold was fabricated by freeze casting hydroxyapatite/barium titanate (HA/BT) suspensions. The highest compressive strength and lowest porosity of 14.5MPa and 57.4% with the best parallelism of the pore channels were achieved in the HA10/BT90 composite. HA30/BT70 and HA10/BT90 composites exhibited piezoelectric coefficient d 33 of 1.2 and 2.8pC/N, respectively, both of which were higher than the piezoelectric coefficient of natural bone. Increase of the solid loading of the suspension and solidification velocity led to the improvement of piezoelectric coefficient d 33. Meanwhile, double-templates resulted in the coexistence of lamellar pores and aligned macro-pores, exhibiting the ability to produce an oriented long-range ordered architecture. The manipulation flexibility of this method indicated the potential for customized needs in the application of bone substitute. An MTT assay indicated that the obtained scaffolds had no cytotoxic effects on L929 cells. [Copyright &y& Elsevier]

Abstract: Freeze casting of aqueous suspension was investigated as a method for fabricating hydroxyapatite (HA) porous ceramics with lamellar structures. The rheological properties of HA suspensions employed in the ice-templated process were investigated systematically. Well aligned lamellar pores and dense ceramic walls were obtained successfully in HA porous ceramics with the porosity of 68–81% and compressive strength of 0.9–2.4MPa. The results exhibited a strong correlation between the rheological properties of the employed suspensions and the morphology and mechanical properties of ice-templated porous HA ceramics, in terms of lamellar pore characteristics, porosities and compressive strengths. The ability to produce aligned pores and achieve the manipulation of porous HA microstructures by controlling the rheological parameters were demonstrated, revealing the potential of the ice-templated method for the fabrication of HA scaffolds in biomedical applications. [Copyright &y& Elsevier]