Production of gradient porous silicon nitride ceramics for bone grafting applications

The aim of this study is to produce gradient porous silicon nitride samples with the similar pore structure of bone. In this thesis, the tape casting method was chosen for the production of the gradient porous silicon nitride samples where the porous structure was obtained by addition of two different types pore formers (PVC and PMMA). Three types of tape slurries were prepared; two slurries from different pore formers and one slurry without pore former. Gradient structure prepared by lamination of three tapes. Laminated sample was kept in burn-out for removing polymeric substances and pore formers, then they were sintered under nitrogen atmosphere at 1700 C for 3 hours. Physical (density, porosity, etc.), phase and microstructural properties were characterized. A gradient pore structure successfully obtained according to SEM analysis, a gradual decrease in pore size was obtained along the cross-section of the samples. Also, mercury porosimetry analysis proved the formation of different pore sizes. Cell culture test was done by using osteoblast-like cells. Cytotoxic and biocompatibility behaviors of the sample was evaluated by two methods which are responsible for cell proliferation (WST-1) and cytotoxicity (LDH). The cell proliferation increased and attachment of cells on the surface of the scaffolds was observed. Likewise, the samples did not show any cytotoxic evaluation due to LDH results. As a result, gradient porous silicon nitride samples are biocompatible and have a possibility to using as a bone substitute element. Keywords: Gradient porosity, tape casting, silicon nitride, cytotoxicity, cell proliferation.