Silicon nitride (Si_3N_4> implants have been used in spinal fusion surgery since 2008. The ability to fabricate Si-3N_4 implants with anatomically relevant shapes and controllable architecture can be particularly beneficial in patient-specific applications. In the present study, an aqueous paste composed of Si-3N_4 powder and sintering additives was prepared with the requisite rheology and formed into structures with different shape and architecture.by robocasting. Sintering and hot isostatic pressing (sinter-HIP) produced an almost dense Si_3N_4 phase (density = 3.23 ± 0.01 g/cm~3) with a microstructure composed of fibrous grains. Four-point bending tests of as-fabricated dense beams showed a flexural strength of 552 ± 68 MPa. Together, these results indicate that robocasting combined with sinter-HIP could provide a manufacturing strategy to create SiaN-t implants with controllable shape and architecture for applications in reconstructive surgery.
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