Porous wollastonite–hydroxyapatite bioceramics from a preceramic polymer and micro- or nano-sized fillers

Wollastonite Foams From an Extruded Preceramic Polymer Mixed with CaCO3 Microparticles Assisted by Supercritical Carbon Dioxide

“…[13] It is important to comment on the effect of extrusion on the phase development of the processed silicone þ filler mixtures. As in previous experiments with fillers mixed with solutions of MK polymer, [3,7] the CaCO 3 /silicone weight ratio was chosen in order to yield a CaO/SiO 2 molar ratio slightly below 1 (0.93), as this was found to promote the development of the desired phase, i.e. wollastonite (calcium mono-silicate, CaO/ SiO 2 molar ratio equal to 1), without forming secondary phases (with CaO/SiO 2 molar ratio higher than 1).…”

“…dissolution of the MK polymer in isopropyl alcohol, incorporation of micro-and nanosized CaCO 3 powders in a silicone solution, drying and cold pressing at 40 MPa. [7] Secondary processing experiments concerned CaCO 3 -filled silicone powders, obtained by finely grinding the extrudates, by means of a ball mill (60 min at 450 rpm, Pulverisette 7 planetary ball mill, Fritsch, Idar-Oberstein, Germany). The obtained powders, sieved to a dimension below 100 mm, were processed by cold pressing, or by warm pressing at 20 MPa with or without addition of PMMA microbeads (Cray Valley Waterborne Polymers Department, Atofina Italia, Milan, Italy) having a diameter of 150 mm.…”

“…The presence of such impurity was attributed to the presence of CaO-rich domains, deriving from the decomposition of relatively large particles of calcium carbonate (<10 mm). [7] The use of nanosized CaCO 3 filler particles (90 nm) practically removed this impurity, because of the easier reaction occurring between the smaller CaO domains with the surrounding silicone-derived silica matrix. It should be noted that the extruded sample containing commercial fine but not nanosized CaCO 3 particles, featured mainly wollastonite, with very limited traces of other silicate phases.…”

“…2CaOÁSiO 2 ) than that obtained from CaCO 3 microsized particles. [7,8] Although successful, this approach based on adding nanosized fillers to silicones still has important practical disadvantages. All the cited experiences refer to the introduction of fillers within solutions of silicone resins, based on solvents such as acetone or isopropyl alcohol, that needs to be removed by drying before further processing (e.g., cold or warm-pressing).…”

Development of Composite Scaffolds for Load Bearing Segmental Bone Defects

“…Having a chemical formula (Ca 10 (PO 4 ) 6 (OH) 2 ), stoichiometric HAp has a structure very similar to that of natural bone [24,26,34,[43][44][45]. For this reason, synthetic CaP materials including HAp are FDA-approved and were among the most investigated materials for scaffold composition for over three decades [46][47][48][49][50][51]. CaPs differ from one another in origin, composition, morphology, and physicochemical properties.…”