Local Cellular Responses to Titanium Dioxide from Orthopedic Implants.

We evaluated recently published articles relevant to the biological effects of titanium dioxide (TiO2) particles on local endogenous cells required for normal bone homeostasis, repair, and implant osseointegration. Structural characteristics, size, stability, and agglomeration of TiO2 particles alter the viability and behavior of multiple bone-related cell types. Resulting shifts in bone homeostasis may increase bone resorption and lead to clinical incidents of osteolysis, implant loosening, and joint pain. TiO2 particles that enter cells (through endocytosis or Trojan horse mechanism) may further disrupt implant retention. We propose that cellular responses to titanium-based nanoparticles contribute to pathological mechanisms underlying the aseptic loosening of titanium-based metal implants.