Effect of titanium powder shavings on tissues.

Titanium (Ti) is widely used in the manufacture of odontological and orthopedic implants. Implant corrosion, with the ensuing release of ions to the milieu, is one of the possible causes of implant failure. We demonstrated that commercial titanium dioxide (TiO₂) (Sigma Co,USA): 1) is deposited in organs with macrophagic activity (liver, spleen and lung), 2) is transported in the blood in cells of the phagocytic-mononuclear lineage and 3) induces an increase in the formation of reactive oxygen species (ROS) in alveolar macrophages. The aim of the present study was to a) develop a model that accurately reproduces the corrosion process that occurs on orthopedic and odontological implants and b) compare the effects of commercial TiO₂ and Ti obtained from titanium shavings. Male Wistar rats (approx. 100g body weight (n=10)) were injected i.p. with a suspension of TiO₂ powder (group Ti ), obtained in our laboratory by thermal oxidation of titanium shavings, at a dose of 1.60g/100g body weight. The control group (C) was injected with saline solution. Six months post-injection the following end-points were assessed: 1) Ti in blood cells, 2) deposits of TiO₂ in liver, spleen and lung by light microscopy, 3) generation of ROS in alveolar macrophages by reduction of tetrazolium blue to formazan salts and 4) oxidative damage to membranes (lipoperoxidation) by the TBARS assay (tiobarbituric acid reactive species). The study of blood smears revealed the presence of Ti in phagocytic mononuclear cells. The histological study of the organs demonstrated the presence of Ti particles in the parenchyma of organs with no associated tissue alterations. TiO₂ induced a significant increase in generation of ROS (C:37±1.2 vs Ti:66± 7.8) with no associated oxidative damage to membranes (C: 2.1± 0.2 vs Ti: 2.8±0.3 ). These results may be attributed to an adaptive response. The biological response to TiO₂ shavings would reproduce the action of commercial TiO₂ in terms of distribution and effect of corrosion. Grants: F. Roemmers and UBACyT O 020. Acknowledgements: Dr. Gustavo Duffó, National Atomic Energy Commission.