Inflammatory Response to Wear Particles: Comparisons Between Zirconia and Titanium In Vitro

To compare the inflammatory responses of peripheral blood mononuclear cells (PBMCs) subjected to titanium (Ti) and/or zirconia (Zr) particles while growing on Ti or Zr discs.

In total, 240 discs were fabricated at a size of 2 mm in height and 5 mm in diameter. Of the 240 discs, 120 discs were made of Ti (commercially pure [CP] grade 4), and 120 discs were made of Zr (3 mol% yttria-stabilized zirconia polycrystals [3Y-TZP]). The PBMCs were cultured on the two-disc materials, and particles with a size up to 20 mm Ti (99.5% Ti) and 0.1 to 0.2 mm Zr (3Y-TZP) were added to the cultures. The concentration levels of inflammatory cytokines in culture supernatants were measured through Bio-Plex assay (Bio-Rad Laboratories), and light microscopic analysis was performed to detect cell attachment and characterize particle shape and cell-particle interaction.

The inflammatory responses of PBMCs were generally higher when cells were cultured on a Ti surface compared to a Zr surface. In addition, higher cytokine levels were seen when cells were cultured in the presence of Ti particles compared to Zr particles when no discs were used. However, there were only significantly increased levels for three cytokines (MCP-1, IFN-γ, and TNF-α) when particles were added to Ti discs. Higher release of neutrophil extracellular traps (NETs) from neutrophils were seen in presence of Zr particles compared to Ti particles. A reduction in cell death was observed in the presence of Zr particles compared to Ti particles and unstimulated control samples.

The type of growth material and presence of particle affects PBMCs in vitro. Cells seeded on Ti discs and together with Ti particles generated higher levels of inflammatory cytokines compared to the Zr counterparts.