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

Abstract

A glass and a rhenanite-wollastonite glass-ceramic were synthesized with the qualitative composition Na2O-CaO-SiO2-P2O5. Both materials were prepared by reaction sintering under isostatic pressure (RSIP) using powder mixtures. Solid state reactions were complete within a few hours at 950 degrees C under modest pressure. Formation of the glass and crystalline phases was driven by an intermediate, reactive, low viscosity Na2O-SiO2 phase. A reaction mechanism is suggested. Porous materials were obtained with two ranges of pore sizes: 100-200 microm and < or =5 microm in diameter. The glass and the glass-ceramic were corroded in simulated body fluid at 37 degrees C. The evolution of surface features was studied. Gel layers formed on both materials. Corrosion was fastest inside the pores. Microcrystals of apatite were identified by crystal structure analysis and by chemical analysis. During corrosion of the glass-ceramic, rhenanite most likely was converted into apatite. Comparison of these results with published information suggests that the glass and glass-ceramic are bioactive. We suggest that RSIP can be used (a) to control the surface porosity and pore size of bioactive implants, thereby increasing the stability of tissue/implant interfaces; (b) to make glasses and glass-ceramics with new properties; and (c) to make near net-shape materials.

Hydroxyapatite and tricalcium phosphate composites with bioactive glass as second phase: State of the art and current applications

“…The phase analysis revealed that the glass and the b-TCP reacted during the thermal treatment, giving rise to the formation of rhenanite (NaCaPO 4 ) and wollastonite (CaSiO 3 ), similarly to what has been reported in the literature for analogous HA/bioglass composites. 133,294 The reaction mechanism, originally proposed by Gong et al, 294 is described by the following equations:…”

Advances in Porous Biomaterials for Dental and Orthopaedic Applications

“…Brittleness and slow degradation rates are disadvantages associated with their use. Gong et al fabricated glass implants with 5% porosity and pores that ranged from 100–200 µm to the <10 µm range, and also glass-ceramic implants with macropores (100–200 µm) and micropores (<5 µm) [110]. Glassy carbon pellets with 40% porosity induced bone in-growth in tibia defects in rabbits [111].…”

Change of phase composition and morphology of sonochemically synthesised hydroxyapatite nanoparticles with glycosaminoglycans during thermal treatment

“…28 Glass ceramics containing NaCaPO 4 were also reported to be bioactive. 29,30 Therefore, the resulting glass ceramic powders from the starting nanoparticles possess high biocompatibility.…”