Incorporation of 45S5 bioglass via sol-gel in ß-TCP scaffolds: Bioactivity and antimicrobial activity evaluation.

In this work, ß-TCP (ß-tricalcium phosphate) bioresorbable scaffolds were prepared by the gel casting method. Then, they were impregnated with a 45S5 bioglass sol gel solution to improve biocompatibility and promote bioactivity and antimicrobial activity. The ß-TCP scaffolds had an apparent porosity of 72%, and after the incorporation of the bioglass, this porosity was maintained. The elements of the bioglass were incorporated into ß-TCP matrix and there was a partial transformation from the ß-TCP phase to the α-TCP (α-tricalcium phosphate) phase, besides the formation of bioactive calcium and sodium­calcium silicates. The scaffolds ß-TCP with 45S5 bioglass incorporated (ß-TCP/45S5) did not show a reduction in their values of mechanical strength and Weibull modulus, despite the partial transformation to the α-TCP phase. Bioactivity, cell viability, and antimicrobial activity improved significantly for the ß-TCP/45S5 scaffold comparing to the scaffold without the bioglass. The mineralization of carbonated hydroxyapatite was verified in Simulated Body Fluid (SBF). The cell viability, evaluated by the reduction of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide - MTT in MG63 cells, increased by 178%, and ß-TCP/45S5 scaffold also enhanced cell activity and osteoblast differentiation observed by means of total protein contend and alkaline phosphatase activity, respectively. The formation of growth inhibition zones was also observed in the disk diffusion assay for three tested microorganisms: Staphylococcus aureus, Escherichia coli and Candida albicans. To conclude, the vacuum impregnation method in 45S5 bioglass sol gel solution was effective in penetrating all the interconnected macroporosity of the scaffolds and covering the surface of the struts, which improved their biological properties in vitro, bioactivity and antibacterial activity, without reducing mechanical strength and porosity values. Thus, the ß-TCP/45S5 scaffolds are shown as potential candidates for use in tissue engineering, mainly in bone tissue regeneration and recovery.

Silica infiltration in partially stabilized zirconia: Effect of hydrothermal aging on mechanical properties.

It aimed to evaluate if silica infiltration might influence the hydrothermal degradation of zirconia by determining: the phases formed, hardness, microstructure, and flexural strength of a 3Y-TZP. Yttria partially stabilized zirconia discs (1.2 mm thickness x 13 mm diameter) (InCeram YZ, Vita Zanhfabrik) were produced and assigned into 6 groups, considering 2 factors: silica infiltration in 2 levels (as-sintered or infiltration) and hydrothermal aging (LTD-Low Temperature Degradation) in 3 levels (baseline, aging at 132 °C for 35 h or 140 h). All the groups were subjected to the biaxial flexural test (n = 30), and Vickers hardness (n = 42). Weibull analysis was performed to determine the Weibull moduli (m) and characteristic strenghts (σ0). The specimens were characterized by scanning electron microscopy (SEM) to evaluate microstructure and X-ray diffraction (XRD) for phases percentages determination. For as-sintered condition: there was saturation of the amount of monoclinic zirconia after 35 h of hydrothermal aging, with 66% of monoclinic zirconia formed on the surface. LTD generated a progressive reduction in hardness over time; flexural strength was increased by the 35-h treatment (baseline: 974 MPa; 35 h: 1161.5 MPa), but, the 140 °C treatment was deleterious (698.5 MPa). On the other hand, the infiltrated specimens had an increase in the amount of cubic zirconia on the surface and showed 26% (35h) and 31% (140h) of monoclinic zirconia after the hydrothermal aging ; the strength was kept unaltered after LTD-35 h (935.9 MPa) and an increase was observed after LTD-140 h (1033.6 MPa); the hardness values had no statistically significant changes during the process. Thus, one can concludes that the silica infiltration can prevent the decrease in the mechanical properties due to the LTD on partially stabilized zirconia materials.