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Using a simple and innovative sandblasting process, disks of monolithic biomedical silicon nitride (β-Si 3 N 4) were texturized with a matrix of regular, discrete square trenches with a total depth in the range of hundreds of microns. The process consisted of sandblasting Si 3 N 4 substrates through a stainless-steel wire-mesh (150 or 200 μm) using abrasive silicon carbide powders (α -SiC, ∼40 μm) under 1,034 kPa (150 psi) of gas pressure. The depth of the porosities could be controlled varying both the treatment time and the distance from the surface. Part of the samples were then filled with 45S5 Bioglass® powders to improve the osteointegration and stimulate the production of bone tissue. Due to the increased macroscopic and microscopic roughness, biological testing using human osteosarcoma cells (SaOS-2) showed improved cell proliferation and greater production of both mineral (hydroxyapatite) and organic (collagen) phases on the patterned surfaces compared to untreated β-Si 3 N 4 or to the biomedical titanium control samples. Both of these effects were further enhanced when the porosities were filled with Bioglass®. • Textured sandblasting has been used for the first time on the surface of silicon nitride. • A steel wire mesh was used to mask the silicon nitride surface during processing. • The textured surface proved to be more osteoinductive compared to polished silicon nitride. • Addition of 45S5 bioglass further enhanced the production of bone tissue by SAOS-2 osteosarcoma cells. [ABSTRACT FROM AUTHOR]

The surface chemistry of silicon nitride plays an important role in stimulating osteoblasts to proliferate and produce bone tissue with improved efficiency. This property, which is advantageous in spinal fusion surgery has a chemical origin and is a direct consequence of the cleavage of covalent S N bonds in an aqueous environment. Building upon a wealth of published research on the stimulation of osteoblastic activity by silicon, the aim of this paper is to explore the role of nitrogen and, more specifically, the N/Si atomic ratio on the osteogenic response of Si 3 N 4. The surface stoichiometry of Si 3 N 4 was gradually altered toward a silicon-rich composition by systematically treating the Si 3 N 4 surface with a high-power pulsed laser in an Ar gas atmosphere (i.e., operated at different pulse times, spot sizes, and voltages). Different analytical probes were used to characterize the surface including X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and energy dispersive X-ray spectroscopy (EDS). Osteoconductivity was tested in vitro using SaOS-2 osteosarcoma cells, and samples with different surface stoichiometry were compared for their osteogenic response. These experiments clearly indicated a fundamental role for nitrogen off-stoichiometry in osteogenesis, and showed that both cell proliferation and growth of bone tissue diminished with decreasing nitrogen content. Unlabelled Image • Silicon nitride surfaces were successfully treated using a ND:YAG pulsed laser. • The pulsed laser treatment resulted in a Si-enriched material. • Metallic silicon domains are formed on the surface of silicon nitride after treatment. • Si-rich areas showed poorer osteogenic capabilities. [ABSTRACT FROM AUTHOR]