BIOACTIVE GLASS-CERAMIC SCAFFOLDS WITH HIGH-STRENGTH FOR ORTHOPEDIC APPLICATIONS

This study aims to produce 45S5 bioactive glass scaffolds (45% SiO2-24.5% CaO-24.5% Na2O-6 % P2O5) through a novel process of powder technology and polymer foaming, patented by the IMI (Industrial Materials Institute, NRC). Initially, various foaming agent/binder/bioglass powder ratios were proved and the optimal ratio was 0.5/54.5/45.0 in wt. %, respectively. The mixing of the powders was carried out in a shaker-mixer and it was compacted in alumina molds. The samples obtained were submitted to a heat treatment in two stages, the first one, foaming, and the second one, pyrolysis and sintering in the same thermal profile, with the goal of obtaining scaffolds with mechanical properties and a bioactive response by immersion in SBF appropriated for orthopedic applications. The sintering temperature of scaffolds was 975 degrees C. Then, the scaffolds were machined to obtain uniform cylindrical samples for mechanical testing and cut into tablets of 3 mm in thickness that were immersed in SBF for bioactivity tests for 0, 1, 3, 7, 14, 21 and 28 days. The characterization of scaffolds before immersion in SBF was performed by scanning electron microscopy (SEM) and microtomography (mu CT), also they were tested for compression, and measurement of density and porosity. After immersion the samples were observed with SEM and analyzed by EDS, X-ray diffraction (XRD) and infrared spectroscopy (FT-IR), also the mass variation was estimated. The scaffolds obtained by the experimental method described above, showed a 55 to 65% interconnected porosity and an average compressive strength of 13.78 +/- 2.43 MPa, and showed the formation of hydroxyapatite layer after 7 days of immersion in SBF, fulfilling the requirements to be used as a regenerative scaffold. The proposed method of powder technology and polymer foaming, allows controlling the porosity, pore size and compression strength of the scaffolds by varying the ratio foaming agent/binder/bioglass powder and sintering temperature.