Porous bioactive glass and glass-ceramics made by reaction sintering under pressure

Construction of Inorganic Bulks through Coalescence of Particle Precursors

Bulk inorganic materials play important roles in human society, and their construction is commonly achieved by the coalescence of inorganic nano- or micro-sized particles. Understanding the coalescence process promotes the elimination of particle interfaces, leading to continuous bulk phases with improved functions. In this review, we mainly focus on the coalescence of ceramic and metal materials for bulk construction. The basic knowledge of coalescent mechanism on inorganic materials is briefly introduced. Then, the properties of the inorganic precursors, which determine the coalescent behaviors of inorganic phases, are discussed from the views of particle interface, size, crystallinity, and orientation. The relationships between fundamental discoveries and industrial applications are emphasized. Based upon the understandings, the applications of inorganic bulk materials produced by the coalescence of their particle precursors are further presented. In conclusion, the challenges of particle coalescence for bulk material construction are presented, and the connection between recent fundamental findings and industrial applications is highlighted, aiming to provide an insightful outlook for the future development of functional inorganic materials.

Biocompatibility of biphasic α,β-tricalcium phosphate ceramics in vitro

The biocompatibility of biphasic α,β-tricalcium phosphate ceramics, obtained by annealing a compact preform based on β-tricalcium phosphate powder, was studied in vitro. It was found that within 10–30 days the adhesion of primary dental pulp stem cells located on the surface of biphasic α,β-tricalcium phosphate ceramics is suppressed. Decrease of the cell number on the surface of biphasic α,β-tricalcium phosphate ceramics, most likely, can be associated with both the pH level (acidic) as a result of hydrolysis of the more soluble phase of α-tricalcium phosphate and with the nature of surface that changes as a result of the formation and growth of hydroxyapatite crystals.

•

In vitro tests of biphasic α,β-tricalcium phosphate ceramics enriched with 65% of α-Ca₃(PO4)² modification were carried out.

•

Surface morphology of α,β-tricalcium phosphate ceramics gradually changed during in vitro tests for 30 days.

•

Sharp edges of hydroxyapatite plate crystallites formed at the surface of ceramics suppressed the cell activity.

•

Acidification near the surface of ceramics containing biodegradable α-tricalcium phosphate suppressed the cell activity.

•

Acidifying α-tricalcium phosphate is a perspective phase of ceramic composites in combination with alkalinizing phases.

Synthesis of novel tricalcium phosphate-bioactive glass composite and functionalization with rhBMP-2

A functionalization is required for calcium phosphate-based bone substitute materials to achieve an entire bone remodeling. In this study it was hypothesized that a tailored composite of tricalcium phosphate and a bioactive glass can be loaded sufficiently with rhBMP-2 for functionalization. A composite of 40 wt% tricalcium phosphate and 60 wt% bioactive glass resulted in two crystalline phases, wollastonite and rhenanite after sintering. SEM analysis of the composite's surface revealed a spongious bone-like morphology after treatment with different acids. RhBMP-2 was immobilized non-covalently by treating with chrome sulfuric acid (CSA) and 3-aminopropyltriethoxysilane (APS) and covalently by treating with CSA/APS, and additionally with 1,1'-carbonyldiimidazole. It was proved that samples containing non-covalently immobilized rhBMP-2 on the surface exhibit significant biological activity in contrast to the samples with covalently bound protein on the surface. We conclude that a tailored composite of tricalcium phosphate and bioactive glass can be loaded sufficiently with BMP-2.

Advances in Porous Biomaterials for Dental and Orthopaedic Applications

The connective hard tissues bone and teeth are highly porous on a micrometer scale, but show high values of compression strength at a relatively low weight. The fabrication of porous materials has been actively researched and different processes have been developed that vary in preparation complexity and also in the type of porous material that they produce. Methodologies are available for determination of pore properties. The purpose of the paper is to give an overview of these methods, the role of porosity in natural porous materials and the effect of pore properties on the living tissues. The minimum pore size required to allow the ingrowth of mineralized tissue seems to be in the order of 50 µm: larger pore sizes seem to improve speed and depth of penetration of mineralized tissues into the biomaterial, but on the other hand impair the mechanical properties. The optimal pore size is therefore dependent on the application and the used material.

Biomaterials in orthopaedics

At present, strong requirements in orthopaedics are still to be met, both in bone and joint substitution and in the repair and regeneration of bone defects. In this framework, tremendous advances in the biomaterials field have been made in the last 50 years where materials intended for biomedical purposes have evolved through three different generations, namely first generation (bioinert materials), second generation (bioactive and biodegradable materials) and third generation (materials designed to stimulate specific responses at the molecular level). In this review, the evolution of different metals, ceramics and polymers most commonly used in orthopaedic applications is discussed, as well as the different approaches used to fulfil the challenges faced by this medical field.

A new rhenanite (β-NaCaPO4) and hydroxyapatite biphasic biomaterial for skeletal repair

Biphasic beta-rhenanite (beta-NaCaPO(4))-hydroxyapatite (Ca(10)(PO(4))(6)(OH)(2)) biomaterials were prepared by using a one-pot, solution-based synthesis procedure at the physiological pH of 7.4, followed by low-temperature (300-600 degrees C) calcination in air for 6 h. Calcination was for the sole purpose of crystallization. An aqueous solution of Ca(NO(3))(2). 4H(2)O was rapidly added to a solution of Na(2)HPO(4) and NaHCO(3), followed by immediate removal of gel-like, poorly-crystallized precursor precipitates from the mother liquors of pH 7.4. Freeze-dried precursors were found to be nanosize with an average particle size of 45 nm and a surface area of 128 m(2)/g. Upon calcination in air, precursor powders crystallized into biphasic (60% HA-40% rhenanite) biomaterials, while retaining their submicron particle sizes and high surface areas. beta-rhenanite is a high solubility sodium calcium phosphate phase. Samples were characterized by XRD, FTIR, SEM, TEM, ICP-AES, TG, DTA, DSC, and surface area measurements.

New macroporous calcium phosphate glass ceramic for guided bone regeneration

This work describes a method to obtain macroporous resorbable glass and glass ceramic scaffolds with controlled biodegradability for tissue engineering applications. The constructs consisted of glass and glass ceramics in the system P(2)O(5)-CaO-Na(2)O-TiO(2) and they were prepared by foaming a slurry of glass particles by addition of a H(2)O(2) solution, and subsequent sintering of the porous structures obtained. Different thermal treatments were applied to control the degree of devitrification of the glass. The resultant materials showed a porosity percentage between 40% and 55% with a wide variety of pores ranging from 20 to 500 microm in diameter as determined by SEM and Image Analysis. The resulting constructs were predominantly formed by a vitreous phase, although small amounts of calcium metaphosphate and pyrophosphates were detected by X-ray diffraction and Raman spectroscopy after the sintering process. The biological response was also evaluated by means of the MTT test, the material showed a non-cytotoxic effect.